Network Structure

The network structure for a CDMA2000 system that supports 2.5G and 3G
has all the traditional voice elements associated with 2G wireless voice systems.
However, the introduction of a packet network requires the additional
network equipment to provide the connectivity between the radio access
network and the data network, whether it is public or private.
Obviously, or maybe it’s not obvious, numerous IP network configurations
can, will, and are being utilized for the support of 2.5G and 3G. The
reason for many different configurations lies in the fact that the information
is packet-based and therefore can be shipped between different company
networks or kept localized. Of course, the issue of the required
throughput and the physical interfaces is also a location dependant.
The packet network is often called the IP network, the IP access network,
or the carrier IP network, depending on your particular situation. However,
the fundamental premise is that the packet network needs to support the
transport and treatment of the packets in the chosen configuration.
Because numerous implementation methods are available for configuring
the packet network, only three main variants will be covered. The main
variants of a network configuration can then be modified to meet your particular
requirements. For example, it might be best to send all Internet traffic
to a local ISP, and virtual private network (VPN) applications, depending
on the treatment required, can be brought to one centralized location for
distribution on, say, an Asynchronous Transfer Mode (ATM) network when
connection to a corporate local area network (LAN) is required.
The three main variants in configuring a CDMA2000 network are as
follows:
■ Distributed
■ Regional
■ Centralized

The regional and centralized variants are similar in concept, except that
the centralized variant is an aggregation of several potential regional networks.
Some of the determinations for deciding on which variant to implement
is determined based on the following issues:
■ Services supported
■ Traffic volume
■ Location of PDSN
■ Commercial interconnection agreements
■ Network reliability and availability
Regardless of which configuration is utilized, it will need a router for the
backbone and, of course, a gateway for all of the offnet service delivery and
reception.
The following sections contain simplified figures and descriptions of the
three major network configuration variants that should be considered for a
CDMA2000 system. In all likelihood, the network architecture, will be initially
dictated by the existing 2G system that is in place. When reviewing
the network figures, the traditional voice networks and the packet networks
have implied different structures. The reason is that a packet network
can and should be treated separately from that of the voice transport
network unless Voice over IP (VoIP) is being utilized for internetwork transportation
of voice-based services.