Partial response technology is applied as quadrature partial response (QPR) for a digital fixed wireless system. In order to improve BER characteristics, QPR may be combined with other coding technologies. One such technology is ambiguity zone detection or AZD, which is a simple form of a maximum likelihood (soft) decoder. A detailed explanation of how AZD works follows. A 9-QPR eye diagram and a block diagram of AZD correction are shown in Figs. 8 and 9, respectively.
