  The Medium Access Control protocol of Power Line Communication networks
(defined in Homeplug and IEEE 1901 standards) has received relatively modest
attention from the research community. As a consequence, there is only one
analytic model that complies with the standardised MAC procedures and considers
unsaturated conditions. We identify two important limitations of the existing
analytic model: high computational expense and predicted results just prior to
the predicted saturation point do not correspond to long-term network
performance. In this work, we present a simplification of the previously
defined analytic model of Homeplug MAC able to substantially reduce its
complexity and demonstrate that the previous performance results just before
predicted saturation correspond to a transitory phase. We determine that the
causes of previous misprediction are common analytical assumptions and the
potential occurrence of a transitory phase, that we show to be of extremely
long duration under certain circumstances. We also provide techniques, both
analytical and experimental, to correctly predict long-term behaviour and
analyse the effect of specific Homeplug/IEEE 1901 features on the magnitude of
misprediction errors.
