We consider the transmission of protocol data units in an LTE eNodeB in downlink direction and focus on the radio link control (RLC) and hybrid Automatic-Repeat-Request functionality at layer 2 of the transmission system. We model the associated window flow control of RLC frames in terms of an open queueing network with two stations and describe RLC frames waiting for acceptance by the flow control window by repeated objects collected in an orbit in front of this multi-server queueing network. We describe the correlated arrivals of frames by a general Markovian arrival process and the transfer of data transport blocks along the orthogonal frequency-division multiplexing channels by state-dependent service processes and varying channel capacities. We derive a versatile finite Markovian queueing model and show that its steady-state distribution can be computed in terms of a level-independent QBD process. Then we determine the basic performance metrics of the system in terms of the latter steady-state distribution.