  The widespread proliferation of sensor nodes in the era of Internet of Things
(IoT) coupled with increasing sensor fidelity and data acquisition modality is
expected to generate 3+ Exabytes of data per day by 2018. Since most of these
IoT devices will be wirelessly connected at the last few feet, wireless
communication is an integral part of the future IoT scenario. The
ever-shrinking size of unit computation (Moore's Law) and continued
improvements in efficient communication (Shannon's Law) is expected to harness
the true potential of the IoT revolution and produce dramatic societal impact.
However, reducing size of IoT nodes and lack of significant improvement in
energy-storage density leads to reducing energy-availability. Moreover, smaller
size and energy means less resources available for securing IoT nodes, making
the energy-sparse low-cost leaf nodes of the network as prime targets for
attackers. In this paper, we survey six prominent wireless technologies with
respect to the three dimensions - security, energy efficiency, and
communication capacity. We point out the state-of-the-art, open issues, and the
road ahead for promising research directions.
