  We investigate energy efficient packet scheduling and power allocation
problem for the services which require reliable communication to guarantee a
certain quality of experience (QoE). We establish links between average
transmit power and reliability of data transfer, which depends on both average
amount of data transfer and short term rate guarantees. We consider a
slow-fading point-to-point channel without channel state information at the
transmitter side (CSIT). In the absence of CSIT, the slow fading channel has an
outage probability associated with every transmit power. As a function of data
loss tolerance parameters, and minimum rate and peak power constraints, we
formulate an optimization problem that adapts rate and power to minimize the
average transmit power for the user equipment (UE). Then, a relaxed
optimization problem is formulated where transmission rate is assumed to be
fixed for each packet transmission. We use Markov chain to model constraints of
the optimization problem. The corresponding problem is not convex for both of
the formulated problems, therefore a stochastic optimization technique, namely
the simulated annealing algorithm, is used to solve them. The numerical results
quantify the effect of various system parameters on average transmit power and
show significant energy savings when the service has less stringent
requirements on timely and reliable communication.
