  This survey paper focuses on the estimation schemes in molecular
communications (MC) systems. The existing studies in estimation schemes can be
divided into parameter estimation (e.g., distance, diffusion coefficient, and
flow velocity) and channel estimation. In this paper, we present, for the first
time, a comprehensive survey on i) distance estimation, since distance is the
most widely estimated parameter in current studies, ii) estimation of other
parameters (i.e. the parameters excluding distance), and iii) channel
estimation that focuses on the channel impulse response (CIR). Moreover, we
examine the noise that may impact on the estimation performance and the metrics
applied to evaluate the performance of different estimation schemes. Numerical
results are provided to compare the performance of different distance
estimation schemes. In addition, future research directions in parameter
estimation and channel estimation are identified and discussed.
