This concept, by
the way, is carried forward within the IMS as well, but with a major difference. In the
circuit-switched domain, the subscriber identity is fixed to the facility (the telephone
line) used to access the network. Since this location is fixed, mobility is not possible
within the circuit-switched domain (at least not using today??™s traditional methods).
To access the network, the subscriber only needs to pick up the telephone and begin
dialing. There is no consideration for registration or authentication; these are all
manual processes that take place when the telephone line is ordered. The connection
is then made based on the dialed digits. This is a far departure from the IMS model,
where the subscriber can access the network from any location and facility, and the
subscription tied to the facility itself is not usually the same as the subscriber accessing
the network.
This is different for wireless, however. In a wireless network, the subscriber can be
anyplace within the home network, or in another network. We will talk about the wireless
model later, as there are many obvious differences between wireline and wireless
challenges.
To route a circuit-switched call to the IMS, there needs to be interaction between
the circuit-switched domain and the packet domain, and then the IMS domain. There
may be cases where the circuit-switched domain connects directly into the IMS domain
through gateways, but it is more likely that initially these connections will be made
through VoIP connections.
Pages:
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117