Christopher D. Long

A data broadcasting system expanding the information capacity of existing analog communication systems

This paper presents the physical layer functions powering a new wireless data broadcasting system over analog television signals, referred to as dNTSC system (for data over National Television System Committee (NTSC) standard). Novel data insertion techniques at the transmitter and data extraction techniques at the receiver allow data rates of 1-4 Mbps that coexist with existing analog transmission but do not adversely affect normal television reception. Novel digital signal processing (DSP) techniques include a video abatement system that reduces data-to-video crosstalk for unimpaired analog television reception, adaptive nonlinear amplifier compensation, and advanced video cancellation and adaptive data equalization methods in the receiver. An analysis of the dNTSC system through noisy, multipath channels reveals the subtleties of the dNTSC system, compared to a conventional, dedicated digital communication link.

Soft decision approaches for blind adaptive decision feedback equalizers

We consider joint blind optimization schemes for decision feedback equalizer (DFE) coefficients and decision device, and propose adaptive solutions based on a soft decision device which combines a blind infinite impulse response (IIR) filtering adaptation and the conventional decision directed (DD) DFE adaptation. The benefits of our approach are mainly three-fold: (1) the initialization of DFE taps does not rely on a training sequence; (2) the transition between the (re)initialization period and the tracking period is continuous and consequently the equalizer exhibits robust performance under sudden time variation in the multipath channel; (3) the optimized soft decision device mitigates error propagation of the DFE and further reduces the mean square error (MSE) of the DFE.