Patent ID: 8351495
Filing Date: 2013-01-08
Classification: H04L

Abstract:
1. A method for detection and analysis of interference and noise in a received signal within a bandwidth of a predetermined communication channel, the method comprising: complex down-conversion of the received signal to an in-phase and quadrature (IQ) sampled signal; low pass filtering and down-sampling the IQ sampled signal to generate a decimated IQ sampled signal having a sample rate commensurate with the bandwidth of the signal; storing at least a portion of the decimated IQ sampled signal in a first data storage element; extracting and recovering a symbol timing of the received decimated IQ sampled signal to generate a complex data stream having a sample rate twice that of the received symbol rate, and which is synchronized to coincide with symbol transition instants, and an estimate of the sample rate ratio between a received symbol rate and a decimated IQ sample rate; extracting and recovering a carrier phase and frequency offset using a carrier phase recovery and synchronization (CARS) digital phase locked loop, and generating soft symbol decisions delivered at the received symbol rate; capturing at least a portion of the soft symbol decisions from the carrier phase recovery and synchronization (CARS) digital phase locked loop in a second data storage element; reading the first data storage element and obtaining a decimator data set and reading the second data storage element and obtaining a symbol decisions data set; generating hard symbol decisions based on the soft symbol decisions data set; increasing a sampling rate of the hard symbol set of data to generate up-sampled hard symbol data; filtering the up-sampled hard symbol data using data shaping filter characteristics employed in a transmitting modulator, the data shaping filter characteristics being provided in the demodulator and cancellation algorithm; interpolating the up-sampled and filtered data to an effective sample rate, the effective sample rate being substantially equal to that of the decimator data set, the required interpolating factor being known from the estimate of the sample rate ratio available from the symbol timing recovery and synchronization digital phase locked loop; adjusting a signal level of the interpolated signal set to achieve amplitude parity with that of the decimator data set; estimating a relative delay, in samples, between the interpolated CARS data and the decimator data set by correlating the decimator data set with the interpolated symbol decision data set; adaptively equalizing the decimator data set to correlate with the interpolated CARS data set in time, amplitude, and phase so as to produce a set of taps for an equalizing filter; convolving the equalizing filter taps with the decimator data set to produce an equalized decimator data set; and cancelling the interpolated CARS data set from the equalized decimator data set to obtain a residue signal containing the received noise and interference.