HOW CAN GUARD PERIODS BE CREATED FOR LTE TDD MODE OF OPERATION?

The second sub-frame of the LTE TDD frame structure contains three special fields.

• DwPTS
• UpPTS and
• Guard period (GP)

The total duration of these special fields is 1ms. The length of the guard period (GP) can be increased at the expense of DwPTS and/or UpPTS with OFDM symbol granularity. However, this creates only a guard period at the switch from DL to UL. To create a guard period at the switch from UL to DL, the eNodeB uses the normal timing advance mechanism to advance the terminal transmission so that they start earlier. This means that the guard period at the switch from UL to DL may be increased at the expense of the guard period at the switch from DL to UL. It also means that a UE with zero roundtrip propagation delay will have a timing advance equal to the duration of the guard period at the switch from UL to DL, as shown in figure below.

The GP configured in the special sub-frame is thus shared between the guard periods at the switches.