This paper investigates a system proposal for transmitting digital high-definition television (HDTV) signals over terrestrial UHF channels. We compare uncoded 16-QAM and trellis-coded 32-CROSS modulation in conjunction with an orthogonal frequency division multiplexing (OFDM) procedure. Our simulations show the influence of the nonlinear distortions introduced by the high-power amplifier (HPA) of the transmitter. As HPA we consider a travelling wave tube amplifier (TWTA) and a solid state power amplifier (SSPA). The characteristics of the channel for HDTV in a single frequency network (SFN) is simulated using a timeinvariant multipath model.
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AbstractThe pa.per describes propa.ga,tion experiments pcrformed on a test link using different diversity configiirations. The results for the angle-diversity ant.cnna showed that the dispersive na,ture of the fading is ma.inly ca.used by ground reflectlions or ray bending a.t, ground-based layers. Outage calciilat.ions were performed for 16 QAM and 256 QAhl digital radio systems with different pa.rametcrs using the observed propagation cha.nne1 chara.cterist,ics. The rcsults showed tha.t propa.gation impairments can strongly be reduced by a.ngle-diversity reception a.s compared with single reception or horizonta.1 spacc diversity. Vertical spa.ce diversitay with a 1a.rge antenna separation, however, outperformed angle diversitmy, a t least, for the bea,m oricnta.tions chosen in this expcriincnt,.
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