The theory of transmission fluctuation spectrometry (TFS) was recently developed for particle size analysis in dilute flowing particle suspensions, whereby the statistical transmission fluctuations are used to extract the particle size distribution and particle concentration. This study addresses the high concentration effects on TFS. As a first part of this publication, the steric interactions between particles within the same monolayer are investigated by introducing a 2-dimensional particle-particle pair correlation function (PPCF), which describes the monolayer structure. As a result, the expression for the expectancy of the transmission square (ETS) through a monolayer is extended to high concentrations. The transmission fluctuation spectrum is found to be influenced by the monolayer structure, which is determined by the particle concentration and the particle-particle interaction potentials.