  In recent years, a large number of smart devices will be connected in
Internet of Things (IoT) using an ad hoc network, which needs more frequency
spectra. The cognitive radio (CR) technology can improve spectrum utilization
in an opportunistic communication manner for IoT, forming a promising paradigm
known as cognitive radio ad hoc networks,CRAHNs. However, dynamic spectrum
availability and mobile devices/persons make it difficult to develop an
efficient data transmission scheme for CRAHNs under an obstacle environment.
Opportunistic routing can leverage the broadcast nature of wireless channels to
enhance network performance. Inspired by this, in this paper, we propose an
Obstacle aware Opportunistic Data Transmission scheme (OODT) in CRAHNs from a
computational geometry perspective, considering energy efficiency and social
features. In the proposed scheme, we exploit a new routing metric, which is
based on an obstacle avoiding algorithm using a polygon boundary 1-searcher
technology, and an auction model for selecting forwarding candidates. In
addition, we prove that the candidate selection problem is NP-hard and propose
a heuristic algorithm for candidate selection. The simulation results show that
the proposed scheme can achieve better performance than existing schemes.
