  A method of channel polarization, proposed by Arikan, allows us to construct
efficient capacity-achieving channel codes. In the original work, binary input
discrete memoryless channels are considered. A special case of $q$-ary channel
polarization is considered by Sasoglu, Telatar, and Arikan. In this paper, we
consider more general channel polarization on $q$-ary channels. We further show
explicit constructions using Reed-Solomon codes, on which asymptotically fast
channel polarization is induced.
