Fast Rendezvous for Spectrum-Agile IoT Devices with Limited Channel Hopping Capability
Sigit Aryo Pambudi, Wenve Wang, Cliff Wang · 2018
The explosive number of IoT nodes and adoption of software-defined radio have enabled an efficient method of exploiting idle frequency spectrums called dynamic spectrum access (DSA). The foremost problem in DSA is for a pair of nodes to rendezvous and form a control channel prior to communication. Existing schemes require a channel hopping (CH) pattern with length O(N2), which is overly complex especially when the number of channels N is large. Moreover, the CH patterns are designed assuming DSA nodes have unlimited CH capability, which is hardly satisfied by nodes with long frequency switching time and limited sensing capacity. In this paper, we design a low-complexity rendezvous scheme that account for CH capability limits. The CH capability is captured using spectrum slice graphs that describe the possible channels for the next hop, given the currently-visited channel. By viewing the CH patterns as random walks over the spectrum graphs, we assign the walks with optimal transition probabilities that achieve the smallest rendezvous delay. The resulting symmetric random CH (S-RCH) scheme, which is suitable for IoT nodes without predetermined roles, achieves a lower rendezvous delay than existing Modular Modified Clock (MMC) scheme and offers more than 80 % successful rendezvous in mobile networks.