CDPD Roaming Management
Contributed by Yi-Bing Lin
The
CDPD
roaming management is achieved by two functions:
the Mobile Home Function (MHF)
and the Mobile Serving Function (MSF).
An
M-ES
is identified by a distinct
Network Entity Identifier (NEI). Every NEI is
associated with a home
MDIS.
The home MDIS maintains a Location Directory to record
the address of the current serving MDIS for each of its homed M-ESs
(this procedure is referred to as
the Location Directory Service). The M-ES may roam away from its
home MDIS and visit other MDIS. The visited MDIS maintains a
Registration Directory to keep track of all visiting M-ESs
(this procedure is referred to as the Registration
Directory Service in the MHF).
Location Registration
The CDPD location registration procedure is described in the following steps:
Step 1:
From the channel stream, an M-ES identifies its location (the
address of the serving MDIS). When the M-ES moves to another serving area,
it registers at the Registration Directory of the current serving MDIS
(the Registration Service in the
MSF).
Step 2:
The serving MDIS then notifies the home MDIS of the current location of the
M-ES, and the Location Directory of the home MDIS is updated (the Registration
Service in the MHF).
Step 3:
The home MDIS then sends a message to
the old serving MDIS to delete the M-ES record of the Registration Directory
of the old MDIS.
NPDU Forwarding
Packet forwarding or Network Protocol Data Unit
(NPDU) forwarding is described in the following steps:
Step 1:
To route an NPDU from the originating MDIS
to an M-ES, the NPDU is first routed to
the home MDIS according to the NEI of the M-ES.
Step 2:
If the M-ES is not in the home area, then the address of the current serving
MDIS of the M-ES is identified in the Location Directory.
The NPDU is then encapsulated and tunneled
to the current serving MDIS.
This procedure is referred to as the
Redirection and Forwarding Service in MHF at the home MDIS.
Step 3:
Upon the receipt of the forwarded NPDU, the current serving MDIS decapsulates
the NPDU and routes it to the cell where the M-ES resides.
This process is referred to as the Readdress
Service in MSF at the serving MDIS).
JPL's Wireless Communication Reference Website
©
Yi-Bing Lin (Author) and
Jean-Paul M.G. Linnartz (Ed.), 1996.
