/** \brief UE specific DLSCH scheduling. Retrieves next ue to be schduled from round-robin scheduler and gets the appropriate harq_pid for the subframe from PHY. If the process is active and requires a retransmission, it schedules the retransmission with the same PRB count and MCS as the first transmission. Otherwise it consults RLC for DCCH/DTCH SDUs (status with maximum number of available PRBS), builds the MAC header (timing advance sent by default) and copies