  In this paper an analytical model is introduced to describe the impulse
response of the diffusive channel between a pointwise transmitter and a given
fully-absorbing (FA) receiver in a molecular communication (MC) system. The
presence of neighbouring FA nanomachines in the environment is taken into
account by describing them as sources of negative molecules. The channel
impulse responses of all the receivers are linked in a system of integral
equations. The solution of the system with two receivers is obtained
analytically. For a higher number of receivers the system of integral equations
is solved numerically. It is also shown that the channel impulse response shape
is distorted by the presence of the interferers. For instance, there is a time
shift of the peak in the number of absorbed molecules compared to the case
without interference, as predicted by the proposed model. The analytical
derivations are validated by means of particle based simulations.
