  Collaborative spectrum sensing has been recognized as a promising approach to
improve the sensing performance via exploiting the spatial diversity of the
secondary users. In this study, a new selfishness issue is identified, that
selfish users sense no spectrum in collaborative sensing. For easier
presentation, it's denoted as entropy selfishness. This selfish behavior is
difficult to distinguish, making existing detection based incentive schemes
fail to work. To thwart entropy selfishness in distributed collaborative
sensing, we propose YouSense, a One-Time Pad (OTP) based incentive design that
could naturally isolate entropy selfish users from the honest users without
selfish node detection. The basic idea of YouSense is to construct a trapdoor
one-time pad for each sensing report by combining the original report and a
random key. Such a one-time pad based encryption could prevent entropy selfish
users from accessing the original sensing report while enabling the honest
users to recover the report. Different from traditional cryptography based OTP
which requires the key delivery, YouSense allows an honest user to recover the
pad (or key) by exploiting a unique characteristic of collaborative sensing
that different secondary users share some common observations on the same radio
spectrum. We further extend YouSense to improve the recovery successful rate by
reducing the cardinality of set of the possible pads. By extensive USRP based
experiments, we show that YouSense can successfully thwart entropy selfishness
with low system overhead.
