  In this paper, we consider the bacterial point-to-point communication problem
with one transmitter and one receiver by considering the ligand receptor
binding process. The most commonly investigated signalling model, referred to
as the Level Scenario (LS), uses one type of a molecule with different
concentration levels for signaling. An alternative approach is to employ
multiple types of molecules with a single concentration level, referred to as
the Type Scenario (TS). We investigate the trade-offs between the two scenarios
for the ligand receptor from the capacity point of view. For this purpose, we
evaluate the capacity using numerical algorithms. Moreover, we derive an upper
bound on the capacity of the ligand receptor using a Binomial Channel (BIC)
model using symmetrized Kullback-Leibler (KL) divergence. A lower bound is also
derived when the environment noise is negligible. Finally, we analyse the
effect of blocking of a receptor by a molecule of a different type, by
proposing a new Markov model in the multiple-type signalling.
