Nec USA, Inc.

Nec Corporation

Slobodan Nedic

Nenad Popovic

Samir Kapoor

An Apparatus for non-linear per-bin adaptive equalization in orthogonal multi-carrier data transmission systems with the Nyquist sub-channel spectral shaping and T/2 staggering of in-phase and quadrature components is disclosed. A previously introduced linear equalization embodiments are augmented by up to three, or more decision feed-back filters, to improve performance in presence of narrow-band interference (NBI) in wire-line and wire-less data transmission systems, and to enable exploitation of implicit diversity of multi-path fading channels, both with and without transmitter-end pre-coding. Adaptation properties of per-bin DFE equalization are analyzed by computer simulation for an intermediate number of constituent sub-channels. BER performance comparison between the conventional Orthogonal Frequency Division Multiplication-(OFDM) and (Orthogonal Quadrature Amplitude Modulation (OQAM)-based multi-carrier systems of similar modulation/demodulation complexity and transmission latency is provided and the potential advantage of using spectrally well shaped orthogonal sub-channels in wireless applications is demonstrated.

Per-bin DFE for advanced OQAM-based multi-carrier wireless data transmission systems

An improved method of decoding the Partial-Response Signaling type inter-bin distortion in receiver-end windowed DMT system is disclosed. The method exploits the Maximum Likelihood Sequence Estimation, which yields certain improvements over the conventional DFE-type decoding of PRS signals. Simulation results are shown for the case wherein AWGN is substantially the only impairment. Since in this case the noise samples at the neighboring frequency bin outputs bear correlation of the same type as the correlation introduced among data symbol samples, a trellis imbedded noise prediction/cancellation approach has been devised. It has been shown that performance degradation can be reduced from almost 8 dB to just 1 dB, compared to performance figures with no windowing. Possible applications of this method are for xDSL and wireless OFDM systems.

MLSE decoding of PRS type inter-bin interference in receiver-end windowed DMT system

A receiver for improving the performance of conventional Discrete Multitone Modulation (DMT) based Asymmetric Digital Subscriber Line (ADSL) modems, in the presence of noise and/or interference. A demodulator having an FFT followed by a single-tap-per-bin frequency-domain equalizer is augmented by an additional data-path utilizing windowing or pulse shaping. Windowing is done independently for each symbol over the orthogonality interval and efficiently in the time domain or frequency domain. A decision feedback equalizer at the output of the windowed data-path cancels inter-bin-interference created by windowing.

Receiver for discrete multitone modulated signals having window function

An apparatus for receiving a discrete multi-tone (DMT) signal representative of a series of input symbols and including a plurality of orthogonal sinusoidal subchannels of finite length for each input symbol, the apparatus including a plurality of delay circuits, each operable to receive the DMT signal and produce a delayed DMT signal; a plurality of windowing circuits, each operable to receive a respective one of the delayed DMT signals and produce a windowed DMT signal; at least one finite duration fast Fourier transform (FFT) circuit, operable to receive the windowed DMT signals and produce respective complex signals representing a plurality of bins corresponding to the subchannels of the DMT signal; a plurality of multiplier circuits, each operable to produce a product of (i) a complex factor for compensating for a respective phase shift introduced by a corresponding one of the delay circuits, and (ii) a respective one of the complex signals; an equalizer circuit operable to receive the products from the plurality of multiplier circuits and produce a partial response signaling (PRS) coded signal; and a PRS decoder operable to receive the PRS coded signal and produce output symbols representative of the input symbols.

Growing community of inventors

Plainsboro, NJ, United States of America

Slobodan Nedic