  This work presents a comprehensive performance analysis of diffusion based
direct, dual-hop, and multi-hop molecular communication systems with Brownian
motion and drift in the presence of various distortions such as inter-symbol
interference (ISI), multi-source interference (MSI), and counting errors.
Optimal decision rules are derived employing the likelihood ratio tests (LRTs)
for symbol detection at each of the cooperative as well as the destination
nanomachines. Further, closed-form expressions are also derived for the
probabilities of detection, false alarm at the individual cooperative,
destination nanomachines, as well as the overall end-to-end probability of
error for source-destination communication. The results also characterize the
impact of detection performance of the intermediate cooperative nanomachine(s)
on the end-to-end performance of dual/multi hop diffusive molecular
communication systems. In addition, capacity expressions are also derived for
direct, dual-hop, and multi-hop molecular communication scenarios. Simulation
results are presented to corroborate the theoretical results derived and also,
to yield insights into system performance.
