Section: 6.1.3.5 Timing Advance Command MAC Control Element
Content: The Timing Advance Command MAC control element is identified by MAC PDU subheader with LCID as specified in table 6.2.1-1. It has a fixed size and consists of a single octet defined as follows (figure 6.1.3.5-1): - TAG Identity (TAG Id): This field indicates the TAG Identity of the addressed TAG. The TAG containing the SpCell has the TAG Identity 0. The length of the field is 2 bits; - Timing Advance Command: This field indicates the index value TA (0, 1, 2… 63) used to control the amount of timing adjustment that MAC entity has to apply (see clause 4.2.3 of TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [2]). The length of the field is 6 bits. Figure 6.1.3.5-1: Timing Advance Command MAC control element