  In this letter, we consider the problem of energy detection of unknown
signals in an intervehicular communication (IVC) system over n*Rayleigh fading
channels (also known as cascaded Rayleigh). Novel tight approximations for the
probability of detection are derived for the no-diversity and the maximum ratio
combining (MRC)) diversity schemes. Moreover, we investigate the system
performance when cooperative spectrum sensing (CSS) is considered with and
without imperfect reporting channels. The analytical results show that the
detection reliability is decreased as the fading severity parameter n increases
but reliability is substantially improved when CSS employs MRC schemes.
