Fully adaptive modem receiver using whitening matched filtering
Detector for demodulating a received signal and producing an information data signal with reduced intersymbol interference Patent #: 5546430
ApplicationNo. 979982 filed on 11/26/1997
US Classes:714/795, Viterbi decoding375/233, Decision feedback equalizer375/341, Maximum likelihood decoder or viterbi decoder714/786Forward error correction by tree code (e.g., convolutional)
ExaminersPrimary: Moise, Emmanuel L.
Attorney, Agent or Firm
International ClassesG06F 011/10
AbstractThe invention relates to joint decision feedback equalization and error correction decoding. To minimize error propagation, the invention uses a combination of enhanced soft decisions and delayed tentative hard decisions from the error correction (Viterbi) decoder to cancel intersymbol interference. Soft decisions are obtained by passing the DFE output through a hyperbolic arc tangent (soft) nonlinear device. These are used to suppress intersymbol interference (ISI) due to multipath with small delays. Tentative hard decisions from a Viterbi decoder are used to cancel ISI due to multipath with large delays, thus remedying the increasing effect of error propagation in channels with large delay spreads. When further combined with antenna diversity and a reduced-complexity DFE concept with adaptive feedforward tap assignment, the invention provides high packet throughput against Rayleigh fading, severe delay spreads, and high Doppler rates.