  In cognitive radio networks, rendezvous is a fundamental operation by which
two cognitive users establish a communication link on a commonly-available
channel for communications. Some existing rendezvous algorithms can guarantee
that rendezvous can be completed within finite time and they generate
channel-hopping (CH) sequences based on the whole channel set. However, some
channels may not be available (e.g., they are being used by the licensed users)
and these existing algorithms would randomly replace the unavailable channels
in the CH sequence. This random replacement is not effective, especially when
the number of unavailable channels is large. In this paper, we design a new
rendezvous algorithm that attempts rendezvous on the available channels only
for faster rendezvous. This new algorithm, called Interleaved Sequences based
on Available Channel set (ISAC), constructs an odd sub-sequence and an even
sub-sequence and interleaves these two sub-sequences to compose a CH sequence.
We prove that ISAC provides guaranteed rendezvous (i.e., rendezvous can be
achieved within finite time). We derive the upper bound on the maximum
time-to-rendezvous (MTTR) to be O(m) (m is not greater than Q) under the
symmetric model and O(mn) (n is not greater than Q) under the asymmetric model,
where m and n are the number of available channels of two users and Q is the
total number of channels (i.e., all potentially available channels). We conduct
extensive computer simulation to demonstrate that ISAC gives significantly
smaller MTTR than the existing algorithms.
