QVSB data transmission

It is well-known that conventional double-sideband (DSB) transmission is not bandwidth-efficient; and historically, in applications where bandwidth is relatively scarce, analog single-sideband (SSB) and vestigial-sideband (VSB) techniques have been used. Previously, high-definition television (HDTV) has opted to send its images digitally-employing multi-level, amplitude-shift-keyed, VSB transmission. This paper extends and broadens the digital VSB transmission concept by demonstrating the utility of quadrature-VSB (QVSB), where two independent data streams are placed on sine and cosine VSB carriers-effectively doubling the bandwidth-efficiency, at the expense of inducing a controlled form of intersymbol-interference (ISI). Classes of minimal ISI filtering families for QVSB are defined, which are more restrictive than Nyquist data shaping. Also, it is demonstrated that m-ary QVSB typically achieves the same capacity as m²-ary QDSB, but requires significantly less E_b/N_o.