  In this paper, a two-hop network in which information is transmitted from a
source via a relay to a destination is considered. It is assumed that the
channels are static fading with additive white Gaussian noise. All nodes are
equipped with a single antenna and the Channel State Information (CSI) of each
hop is not available at the corresponding transmitter. The relay is assumed to
be simple, i.e., not capable of data buffering over multiple coding blocks,
water-filling over time, or rescheduling. A commonly used design criterion in
such configurations is the maximization of the average received rate at the
destination. We show that using a continuum of multilevel codes at both the
source and the relay, in conjunction with decode and forward strategy at the
relay, performs optimum in this setup. In addition, we present a scheme to
optimally allocate the available source and relay powers to different levels of
their corresponding codes. The performance of this scheme is evaluated assuming
Rayleigh fading and compared with the previously known strategies.
