  The problem of minimizing queueing delay of opportunistic access of multiple
continuous time Markov channels is considered. A new access policy based on
myopic sensing and adaptive transmission (MS-AT) is proposed. Under the
framework of risk sensitive constrained Markov decision process with effective
bandwidth as a measure of queueing delay, it is shown that MS-AT achieves
simultaneously throughput and delay optimality. It is shown further that both
the effective bandwidth and the throughput of MS-AT are two-segment piece-wise
linear functions of the collision constraint (maximum allowable conditional
collision probability) with the effective bandwidth and throughput coinciding
in the regime of tight collision constraints. Analytical and simulations
comparisons with the myopic sensing and memoryless transmission (MS-MT) policy
which is throughput optimal but delay suboptimal in the regime of tight
collision constraints.
