 this case. 144 VoLTE and ViLTE The TTI bundling function consists of transmitting, in four consecutive sub-frames, four redundancy versions, without waiting for the return of HI information, in order to reduce the value of the jitter. The same modulation and coding scheme and the same frequency band are used for transmission of the four redundancy versions. The TTI bundling function is limited to the transmission for the uplink. The TTI bundling function is not supported for the aggregation of radio channels. In the FDD mode, the number of HARQ processes is reduced to 4 (Figure 4.16). The HI information is transmitted 4 ms after the last redundancy version. If the HI information corresponds to a NACK, the four redundancy versions are retransmitted with a 16 ms delay. Transmission instants of data on PUSCH physical channel number process Reception instants of ACK/NACK on PHICH physical channel Figure 4.16. TTI bundling function in the FDD mode For a color version of the figure, see www.iste.co.uk/perez/volte.zip In the TDD mode, the TTI bundling function is only applicable in configurations 0, 1 and 6 of the time frame. The HARQ processes number is limited to 3 for the configurations 0 and 6 and to 2 for the configuration 1 (Figure 4.17). Radio Interface Procedures Transmission instants of data on PUSCH physical channel Sub-frame number Reception instants of ACK/NACK on PHICH physical channel L01234567890123456789012345678901 process number Figure 4.17. TTI function bundling in the TDD mode for configuration For a color version of the figure, see www.iste.co.uk/perez/volte.zip Service Profiles 5.1. Subscription data 5.1.1. Subscription to the EPS network When subscribing to the evolved packet system (EPS), the user is assigned a private international mobile subscriber identity (IMSI) which is associated with a profile on the telephone service (Figure 5.1). User profile APN-Configuration-Profile APN-Configuration APN-Configuration-Profile PDN-Type Service-Selection Subscriber-Status Network-Access-Mode EPS-Subscri