An Enhanced Fast Multi-Radio Rendezvous Algorithm in Heterogeneous Cognitive Radio Networks

Abstract

In this paper, we propose a fast rendezvous algorithm for a heterogeneous cognitive radio network (CRN), where each user might have more than one radio. One of the well-known problems for most multiradio rendezvous algorithms in the literature is that they are not backward compatible to users with only one radio. To tackle this backward compatibility problem, our approach is a hierarchical construction that groups several time slots into an interval and proposes a novel algorithm to emulate two radios with a single radio in an interval. By doing so, at the interval level, each user behaves as if it had (at least) two radios. For the two-user rendezvous problem in a CRN with ${N}$ commonly labelled channels, the interval length is chosen to be ${M}$ time slots, where ${M=2\lceil \text {log}_{2} (\lceil \text {log}_{2} N \rceil)\rceil +7}$ . We show that the maximum time-to-rendezvous (MTTR) of our algorithm is bounded above by ${9 M \lceil n_{1}/m_{1} \rceil \cdot \lceil n_{2}/m_{2} \rceil }$ time slots, where ${n_{1}}$ (resp. ${n_{2}}$ ) is the number of available channels to user 1 (resp. 2), and ${m_{1}}$ (resp. ${m_{2}}$ ) is the number of radios for user 1 (resp. 2). For the setting that each user is equipped with only one radio and two available channels, our MTTR bound is only ${M}$ and that improves the state-of-the-art bound $16(\lceil \log _{2} \log _{2} N \rceil +1)$ in the literature. By conducting extensive simulations, we show that for the expected time-to-rendezvous, our algorithm is also better than several existing multiradio algorithms.