Section: 2.6 Structure of TLLI
Content: A TLLI is built by the MS or by the SGSN either on the basis of the P-TMSI (local or foreign TLLI), or directly (random or auxiliary TLLI), according to the following rules. The TLLI consists of 32 bits, numbered from 0 to 31 by order of significance, with bit 0 being the LSB. A local TLLI is built by an MS which has a valid P-TMSI as follows: bits 31 down to 30 are set to 1; and bits 29 down to 0 are set equal to bits 29 to 0 of the P-TMSI. A foreign TLLI is built by an MS which has a valid P-TMSI as follows: bit 31 is set to 1 and bit 30 is set to 0; and bits 29 down to 0 are set equal to bits 29 to 0 of the P-TMSI. A random TLLI is built by an MS as follows: bit 31 is set to 0; bits 30 down to 27 are set to 1; and bits 0 to 26 are chosen randomly. An auxiliary TLLI is built by the SGSN as follows: bit 31 is set to 0; bits 30 down to 28 are set to 1; bit 27 is set to 0; and bits 0 to 26 can be assigned independently. Other types of TLLI may be introduced in the future. Part of the TLLI codespace is re-used in GERAN to allow for the inclusion of the GERAN Radio Network Temporary Identifier in RLC/MAC messages. The G-RNTI is defined in 3GPP TS 44.118[ None ]  [29]. The structure of the TLLI is summarised in table 1. Table 1: TLLI structure 'T', 'R', 'A' and 'X' indicate bits which can take any value for the type of TLLI. More precisely, 'T' indicates bits derived from a P-TMSI, 'R' indicates bits chosen randomly, 'A' indicates bits chosen by the SGSN, 'G' indicates bits derived from the assigned G-RNTI and 'X' indicates bits in reserved ranges.