Abstract
We consider the transmission over an unknown frequency-selective
channel of two independent sources with different characteristics:
one source (such as voice) has a low information rate with a strict
delay constraint; the other (such data) has a high rate but without
any delay constraints. We assume that, due to the delay
requirements, the low-rate source must be decoded first and below
a certain error probability. We study a communication system in
which pilot symbols are not present and the low-rate information is
decoded non-coherently. The decoded low-rate codewords are
then used for channel estimation to facilitate coherent decoding of
the high-rate source. For a fixed detection error probability of the
low-rate source, we derive achievable rate expressions for the
high-rate source. We demonstrate a convergence behavior of the
achievable rate of the high-rate source as the decision error
probability of the low-rate source goes to zero. Numerical results
show that the achievable rate of the high-rate source converges to
that achievable by a training-based scheme at moderate decision
error levels.