US 5,255,290 A · Method and apparatus for combined frequency offset and timing offset estimation

Abstract

A method and apparatus for generating a frequency offset estimate and a timing offset estimate from a base band signal. In an important application of the invention, a modulated carrier signal is transmitted over a transmission channel and then received and demodulated to generate the base band signal. The modulated carrier signal comprises data having a transmitted symbol frequency and phase, and a carrier signal modulated by the data. The invention simultaneously generates from the base band signal a frequency offset estimate representing the difference between the transmitted and received carrier signal frequency, and a timing offset estimate representing the difference between the transmitted symbol phase and the recovered symbol phase of the base band signal. In preferred embodiments, the base band signal is a digital signal sampled at a rate which exceeds the Nyquist rate. Typically, a sampling rate of more than two samples per symbol is adequate to meet this condition. A pair of nonlinear operations is performed on this digital base band signal, and the resulting two nonlinear signals are processed to generate the frequency offset and timing offset estimates.

Claims14

Dependent claims

A method for generating a frequency offset estimate and a timing offset estimate from a base band signal, wherein the base band signal is a digital signal r(t) indicative of digital data which have been transmitted with a symbol frequency 1/T and a phase, but which have been received after transmission with a frequency offset error and a timing offset error, wherein the digital signal r(t) is a complex signal having a complex conjugate signal r*(t), including the steps of:

(a) performing a first nonlinear operation on the base band signal to generate a first nonlinear signal;
(b) while performing step (a), performing a second nonlinear operation on the base band signal to generate a second nonlinear signal, wherein the first nonlinear signal has form (r(t))(r*(t-T)), where T=(1/T).sup.-1, and the second nonlinear signal has form (r(t))(r*(t+T));
and
(c) processing the first nonlinear signal and the second nonlinear signal to generate the frequency offset estimate, and simultaneously processing the first nonlinear signal and the second nonlinear signal to generate the timing offset estimate.

1 more element

An apparatus for generating a frequency offset estimate and a timing offset estimate from a base band signal, wherein the base band signal is a digital signal r(t) indicative of digital data which have been transmitted with a symbol frequency 1/T and a phase, but which have been received after transmission with a frequency offset error and a timing offset error, wherein the digital signal r(t) is a complex signal having a complex conjugate signal r*(t), said apparatus including:

first means for performing a first nonlinear operation on the base band signal to generate a first nonlinear signal;
second means, connected in parallel with the first means, for performing a second nonlinear operation on the base band signal to generate a second nonlinear signal, wherein the first nonlinear signal has form (r(t))(r*(t-T)), wherein T=(1/T).sup.-1, and the second nonlinear signal has form (r(t))(r*(t+T));
and
means for processing the first nonlinear signal and the second nonlinear signal to generate, substantially simultaneously, the frequency offset estimate and the timing offset estimate.

1 more element

Dependencies are inferred from the claim text.

Method and apparatus for combined frequency offset and timing offset estimation

Life of this patent

Method and apparatus for combined frequency offset and timing offset estimation

Life of this patent

Abstract

Claims14