there is no need to for UL to DL time gap, let me clarify. It is a HW requirement as there is no switch that takes absolute zero time in switching from Tx to Rx. So, just for that, even in LTE, a guard period is required in UL to DL switch. And since for the sake of simplicity, no frame diagram shows it, this time is taken out of the Guard Period in the Special Subframe after the Dwpts in the DL to UL switch.
The discussions done before were for half duplex eNB, In that case, eNB would not need a gap at UL to DL switch.
