  Various system tasks like interference coordination, handover decisions,
admission control etc. in current cellular networks require precise mid-term
(spanning over a few seconds) performance models. Due to channel-dependent
scheduling at the base station, these performance models are not simple to
obtain. Furthermore, LTE cellular systems are interference-limited, hence, the
way interference is modelled is crucial for the accuracy. In this paper we
present a closed-form analytical performance model for proportional fair
scheduling in OFDMA/LTE networks. The model takes into account a precise SINR
distribution into account. We refine our model with respect to uniform
modulation and coding, as applied in LTE networks. Furthermore, the analytical
analysis is extended also for ultra-dense deployments likely to happen in the
5-th generation of cellular networks. The resulting analytical performance
model is validated by means of simulations considering realistic network
deployments. Compared with related work, our model demonstrates a significantly
higher accuracy for long-term throughput estimation.
