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Consider a P‐TMSI of a GPRS mobile subscriber which is of 32 bits in length. The mapping and deriving of an NRI and a TLLI from a P‐TMSI is shown in Figure 5.5.

 NRI

An NRI is mapped into the Bits 23rd to 14th of a P‐TMSI.

 TLLI

The first two MSBs of a TLLI are set to 1's. The Bits 29th to 0th of a TLLI is mapped into the corresponding bits of a P‐TMSI.

Figure 5.5 GPRS MS identity: mapping of an NRI and TLLI into a P‐TMSI.