Simple IP

Simple IP is similar to the dial-up Internet connections used by many people
over standard landline facilities. Simple IP is where a PPP session is
established between the mobile and the PDSN. The PDSN basically routes
packets to and from the mobile in order to provide end-to-end connectivity
between the mobile and the Internet. A diagram depicting Simple IP is
shown in Figure 7-10.

When using Simple IP, the mobile must be connected to the same
PDSN for the duration of the packet session. If the mobile, while in transit,
moves to a coverage area whose BSC/BTSs are homed out of another
PDSN, the Simple IP connection is lost and needs to be re-established.
The loss of the existing packet session effectively is the same as when the
Internet connection on the landline is terminated and you need to reestablish
the connection.

Let’s refer back to Figure 7-9, which is a simplified model of the simple
IP implementation. Many of the details are left out, but the concept shows
that the mobile is connected to the PDSN using a PPP connection in a besteffort
data delivery method at the agreed-upon transfer rate. The transfer
rate is determined by the subscribers profile, the radio resource availability,
and the radio environment itself.
The IP address of a mobile is linked to the PDSN, which can be static or
DHCP; for Simple IP, the choice is DHCP. A mobile with an active or dormant
data call can transverse around the network, going from cell to cell,
provided it stays within the PDSN’s coverage area. Additionally, the PDSN should support both the Challenge Handshake Authentication Protocol
(CHAP) and the Password Authentication Protocol (PAP).
Simple IP, as indicated, does not enable the subscriber full mobility with
packet data calls. When the subscriber exits the PDSN coverage area, it
must negotiate for a new IP address from the new PDSN, which, of course,
results in the termination of the existing packet session and requires a new
session to begin.

Regarding the radio environment, the CDMA2000 radio network provides
the mobile with a traffic channel that consists of a fundamental channel
and possibly a supplemental channel for higher traffic speeds. To help
explain the use of the Simple IP process, a call flow or a packet session flow
chart is shown in Figure 7-11, which represents a subscriber operating in
his or her home PDSN network. In Figure 7-12, the mobile is considered to
be ROAMing.