  We study the throughput-vs-delay trade-off in an overlay multi-channel
single-secondary-user cognitive radio system. Due to the limited sensing
capabilities of the cognitive radio user, channels are sensed sequentially.
Maximizing the throughput in such a problem is well-studied in the literature.
Yet, in real-time applications, hard delay constraints need to be considered
besides throughput. In this paper, optimal stopping rule and optimal power
allocation are discussed to maximize the secondary user's throughput, subject
to an average delay constraint. We provide a low complexity approach to the
optimal solution of this problem. Simulation results show that this solution
allows the secondary user to meet the delay constraint without sacrificing
throughput significantly. It also shows the benefits of the optimal power
allocation strategy over the constant power allocation strategy.
