Hughes Electronics Corporation

Hughes Aircraft Company

Hughes Network Systems, LLC

Long Huynh

Michael I Parr

Bassel F Beidas

Mark C Davis

David N Critchlow

Fred D Harris

Youngky Kim

John L Watson

Sharath Ananth

Drew Barnett

Filtering loop and method for maintaining synchronization between a receiver and a transmitter reduces overhead and enables more robust operation. The method includes the step of receiving an error signal corresponding to a synchronization parameter. A first order filter is applied to the error signal such that a residual signal results. The method further provides for compensating the residual signal for drift such that the compensated residual signal estimates a rate of change in the residual signal. By compensating the residual signal for drift, difficulties associated with time lag and signal degradation are obviated.

Filter loop structure for synchronization in a mobile communication terminal and a method of using the same

A method for estimating and compensating for a fading communications channel includes the steps of generating matched filter data from a received data burst, interpolating between reference symbols to generate a fading channel estimate from the matched filter data, applying a phase correction to the matched filter data from the fading channel estimate to recover free data from the matched filter data, and performing decision feedback on the free data to improve the fading channel estimate.

Fading communications channel estimation and compensation

A device and method of selecting and deselecting an equalizer in a digital communications receiver. The method includes receiving a receiver signal, estimating an estimated delay spread in the receiver signal, and determining a threshold delay spread. In the event the estimated delay spread exceeds the threshold delay spread, the method includes selecting the equalizer. In the event the estimated delay spread does not exceed the threshold delay spread, the method includes deselecting the equalizer. The method also includes generating a receiver output signal in response to an equalizer signal in the event the equalizer is selected, and generating the receiver output signal in response to the receiver signal in the event the delay spread does not exceed the threshold. The device includes a radio receiver that receives the receiver signal and an analysis circuit coupled to the radio receiver. The analysis circuit estimates the estimated delay spread in the radio signal, and determines the threshold delay spread. The receiver also includes an equalizer that equalizes the receiver signal and generates an equalizer signal in response thereto; a switching device that selects the equalizer in the event the delay spread exceeds the threshold, and deselects the equalizer in the event the delay spread does not exceed the threshold. A system output is further included that generates a receiver output signal in response to the equalizer signal or the receiver signal depending on whether the equalizer is selected.

Receiver selection based on delay spread estimation

A system and method for jointly determining initial tap coefficients for a maximum likelihood sequence estimating equalizer and a timing error of an incoming signal, in one embodiment, receives the incoming signal into a receiver, and locates a known portion within a time frame of the incoming signal. The known portion is compared with a stored representation of the known portion, and with a stored representation of a derivative of the known portion. The initial tap coefficients and timing error of the incoming signal are jointly determined based on the comparing of the known portion with the stored representations, and a subsequent known portion is located within a subsequent time frame of the incoming signal based on the timing error. The initial tap coefficients are passed to a maximum likelihood sequence estimating equalizer.

Joint maximum likelihood channel and timing error estimation

A device and method for receiving a radio signal transmitted over a channel, selecting and deselecting an equalizer, and balancing processing in response to such selection. A radio frequency signal is received from a transmission channel into a receive path, and delay spread in the radio frequency signal is estimated using an analysis circuit. The analysis circuit also determines a threshold delay spread. In the event the estimated delay spread exceeds the threshold delay spread, an equalizer is selected, otherwise the equalizer is deselected. Similarly, in the event the estimated delay spread does not exceed the threshold delay spread, a high complexity processor is selected, otherwise a low complexity processor is selected. If the low complexity processor is selected, an output signal is generated using the low complexity processor, and if the high complexity processor is selected, the output signal is generated using the high complexity processor.

Balanced processing based on receiver selection

A cellular base station (10) in a digital cellular system employs transmitting circuitry in which voice signals (15) are processed at a low frequency level (12) into two separate paths. A first of the low frequency signals is variably delayed (20), and the first and the other low frequency signals are upconverted to radio frequency level (16,22) for transmission over independent time-spaced transmission paths (26,28) to cellular receivers. A receiver downconverts and demodulates the radio frequency diversity signals, and then combines the demodulated diversity signals to generate an equalized combination diversity signal for receiver output processing.

Time division multiple access cellular communication system and method

A device and method of adjusting an equalizer in a digital communications receiver in response to relative velocity between the communications receiver and a communications transmitter. A radio frequency receiver receives a radio frequency signal from the communications transmitter through a communications channel, and an analog to digital converter digitizes a first portion of the radio frequency signal during a first time period, and generates a first data signal made up of digital samples. The analog to digital converter also digitizes a second portion of the radio frequency signal during a second time period and generates a second data signal, also made up of samples. A channel estimator estimates characteristics of the communications channel in response to a portion of the first data signal, and generates a first channel estimate in response thereto. Finally, a processor determines an estimated velocity of the communications receiver relative to the communications transmitter, weights the first channel estimate in response to the estimated velocity, and generates a revised channel estimate in response to the weighting of the first channel estimate and the second data signal.

Growing community of inventors

San Diego, CA, United States of America

Long Huynh