  In this paper, we consider the channel allocation problem for throughput
maximization in cognitive radio networks with hardware-constrained secondary
users. Specifically, we assume that secondary users exploit spectrum holes on a
set of channels where each secondary user can use at most one available channel
for communication. We develop two channel assignment algorithms that can
efficiently utilize spectrum opportunities on these channels. In the first
algorithm, secondary users are assigned distinct sets of channels. We show that
this algorithm achieves the maximum throughput limit if the number of channels
is sufficiently large. In addition, we propose an overlapping channel
assignment algorithm, that can improve the throughput performance compared to
the non-overlapping channel assignment algorithm. In addition, we design a
distributed MAC protocol for access contention resolution and integrate the
derived MAC protocol overhead into the second channel assignment algorithm.
Finally, numerical results are presented to validate the theoretical results
and illustrate the performance gain due to the overlapping channel assignment
algorithm.
