Note: Descriptions are shown in the official language in which they were submitted.
CA 02340577 2001-03-13
Mobile IP Mobility Management at Dormant Hand-Over in CMDA IP-Based
Cellular Packet-Data Network
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to IP-based packet-data cellular
telecommunications, particularly to a method and system for more efficiently
managing a mobile node dormant hand-off in a CDMA packet-data cellular
telecommunications network.
Description of the Related Art
The CDMA 2000 cellular telecommunications network is a third generation
(3G) IP-based cellular telecommunications network that uses the Code Division
Multiple Access (CDMA) radio access technology for providing high-speed
wireless service to mobile stations (MS). The services include interactive and
background type of traffic classes, as well as conversational and streaming
type of
services, such as voice, text, internet and multimedia applications.
An exemplary IP-based CDMA 2000 cellular telecommunications network
includes a plurality of mobile stations herein designated as Mobile Nodes
(MNs)
communicating over a radio interface with Base Transceiver Stations (BTS).
Each
group of one or more BTSs is connected to, and controlled by a Base Station
Controller (BSC) having a Packet Control Function (PCF), which purpose is to
manage the radio resources of each co-operating BTS. One or more Mobile
Switching Centers (MSCs) may be connected to the IP-based CDMA 2000 cellular
packet data telecommunications network for the provision of cellular service
to
subscribers, while a Packet Data Service Node (PDSN) performs the switching
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and routing functions directed to the packet data communications within the
CDMA 2000 cellular telecommunications network.
The CDMA 2000 packet-data cellular telecommunications network
provides Mobile IP service to packet mobile users. Mobile IP service is
provided
over a Point-to-Point Protocol (PPP) connection between the MN and the PDSN.
When a PPP connection is established, negotiation messages are exchanged
between the MN and the PDSN with regards to authentication and compression,
followed by the MN's mobile IP registration. Thereafter, data may be sent from
and to the MN, such as for example during a voice conversation or a file
download. However, the MN becomes dormant when no data is transmitted for a
certain period of time over the PPP connection. In instances when the MN is
dormant, there is no traffic channel assigned to the mobile, although the PPP
connection is maintained in both the MN and the PDSN.
When a mobile node moves within the packet data service area, instances
arise when the MN is moved, or handed-off, from a first serving packet zone to
a
second service packet zone. This scenario involves the establishment of a new
traffic channel between the new serving Base Station Controller (BSC) and the
MN, as well as the establishment of a new PPP connection between the new
serving PDSN and the MN.
Reference is now made to Figure 1, wherein there is shown a nodal
operation and signal flow diagram illustrating the complex and complicated
prior
art method for performing a dormant hand-off for a mobile node. Shown in Fig.
1
is a CDMA 2000 packet data cellular telecommunications network 100
comprising at least one Mobile Node (MN) 110, communicating over an air
(radio)
interFace 112, and via a plurality of Base Transceiver Stations (BTSs, not
shown)
with a plurality of Base Station Controllers (BSCs), such as for example BSCs
114 and 116. The BSCs 114 and 116 may each comprise a Packet Control
Function (PCF), which purpose is to manage the radio resources of each served
BTS. Thus, the combined functionality of a BSC and a PCF is herein designated
as BSC/PCF,
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although in some implementations the BSC and PCF may not be collocated. The
network 100 may further comprise at least one Mobile Switching Center (MSC)
118 and a plurality of Packet Data Service Nodes (PDSNs), such as for example
PDSN 120 and PDSN 122. The BSC/PCFs and the PDSNs may be connected
with each other through an IP-based network 111. For the purpose of better
understanding the present invention, it is assumed that a dormant MN 110 moves
from a first packet zone, wherein it was served by BSC/PCF Source (BSC/PCF-S)
114 and PDSN Source (PDSN-S) 120, to a second packet zone wherein it is to be
served by BSC/PCF Target (BSS/PCF-T) 116 and PDSN Target (PDSN-T) 122.
By dormant MN, it is meant an MN that previously established a Point-to-Point
Protocol (PPP) connection with a PDSN, such as for example with the PDSN-S
120, but that did not exchange data over that connection for a given period of
time,
thus causing the traffic channel between itself and the PDSN 120 to be
dropped,
while the PPP connection was kept active in both the MN and the PDSN-S.
Therefore, when the MN 110 crosses the packet zone boundary at dormant
state, the MN 110 sends an origination request message 124 to the target BSC
116 via a BTS (not shown), for requesting service from BSC/PCF-T 116.
Responsive to the receipt of the origination request message 124, the BSC/PCF-
T
116 replies back to the MN 110 through a BS acknowledgement order message
129, for confirming that it accepts to serve the MN 110. The BSC 116 further
exchanges with the serving MSC 118 serving set up messages 128 and 130,
through which the MSC 118 is requested, and accepts, to support cellular
service
for the MN 110. Since the MN 110 has moved to a new packet zone, the target
BSC 116 selects a new PDSN, such as the target PDSN 122 for providing mobile
IP service for the MN 110, and thus sends an All registration request message
132 to the target PDSN 122 for requesting the set up of an A10 connection
(also
called herein a Radio network Packet data serving node session or connection,
(RP) with the MN 110. Responsive to the receipt of the A11 registration
request
message 132, the target PDSN 122 replies back to the BSC/PCF-T 116 with an
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A11 registration reply message 136. The BSC/PCF-T 116 then sends to the MSC
118 an Assignment Failure message 137 informing the MSC that the MN 110 is
dormant. At this stage, the PDSN-T 122 may begin to send data packets for the
MN 110, action 139. In the prior art technique, the BSC/PCF-T 116 further
signals
the MSC 118 with a BS Service Request 141 for requesting packet data service,
to
which the MSC 118 responds with a BS service response 143 accepting the
provision of packet data service. The MSC 118 further sends a Paging Request
145 to the BSC/PCF-T 116 to establish a mobile terminated packet data call.
Responsive to 145, the BSC/PCF-T 116 further issues a Page Message 149 over
the paging channel, and receives back from the MN 110 a Page Response
Message 151 over the access channel. Upon receipt of message 151, the
BSC/PCF-T 116 places the Page Reponses Message in a Complete L3 Info
Message 153 and sends it to the MSC 118. The BSC/PCF-T 116 also
acknowledges to the MN 110 the receipt of the Page Response Message 151, in
message 155. Responsive to the receipt of the message 153, the MSC finally
requests the establishment of a traffic channel with the MN 110, action 157.
With
reference being now made jointly to Fig. 1.a and Fig. 1.b, channel
establishment
procedures take place in 159 resulting in a traffic channel 161 to be
established
between the MN 110 and the BSC/PCF-T 116. The data packets received from the
PDSN-T 122 in 139, and that were buffered by the BSC/PCF-T 116, may now be
sent to the MN 110, action 163, for the establishment of the new PPP
connection
150 through PPP connection establishment procedure 148.
As it may be seeing, the prior art method for performing a dormant hand-off
in a CDMA 2000 packet-data cellular telecommunications network is complicated
and comprises unnecessary signalling that overuses the network's
communications resources. For example, having a paging procedure involving at
least messages 145, 149, 151, and 153 in order to locate yet again an MN that
just
registered with the BSC/PCF-T 116 is unnecessary.
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It would be advantageous to have simpler method for performing a dormant
hand-off in the CDMA 200 packet-data cellular telecommunications network, that
takes advantage of the information already passed among the network's nodes
for
avoiding signalling associated with the transmission of redundant and
unnecessary information.
The present invention provides such a solution.
Summary of the Invention
It is therefore an object of the present invention to provide In an IP-
based Code Division Multiple Access (CDMA) cellular telecommunications
network, a method for handing-off a dormant Mobile Node (MN) to a target
packet
zone having a Packet Data Service Node (PDSN) and a Base Station Controller
with a Packet Control Function (BSC/PCF), the method comprising the steps of:
transmitting from the dormant MN to the BSC/PCF an origination
request message comprising an indication that the MN is dormant;
responsive to a receipt of the origination request, sending from the
BSC/PCF to the PDSN a registration request message, the registration request
comprising an indication of an identity of the MN and an indication that the
MN is
dormant;
transmitting from the PDSN to the BSC/PCF a registration reply for
requesting an establishment of a traffic channel between the BSC/PCF and the
MN, the registration reply comprising an indication that the PDSN has packet
data
ready to be sent to the MN;
responsive to a receipt of the registration reply by the BSC/PCF,
establishing a traffic channel between the BSC/PCF and the MN.
It is another object of the present invention to provide an IP-based
Code Division Multiple Access (CDMA) cellular telecommunications system
comprising:
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a target packet zone to which a dormant Mobile Node (MN) is being
handed-off from a source packet zone, the target packet zone comprising:
a Base Station Controller having a Packet Control
Function (BSC/PCF), the BSC/PCF receiving an origination
request message from the dormant MN during the hand-off;
and
a Packet Data Service Node (PDSN) receiving from the
BSC/PCF a registration request for requesting packet data
service provision, the registration request comprising an
identification of the MN and an indication that the MN is
dormant;
wherein responsive to the receipt of the registration
request message, the PDSN sends a registration reply
message to the BSC/PCF for requesting an establishment of a
traffic channel between the BSC/PCF and the MN; and
responsive to the receipt of the registration reply by the BSC/PCF,
establishing a traffic channel between the BSC/PCF and the MIN.
Brief Description of the Drawings
For a more detailed understanding of the invention, for further objects and
advantages thereof, reference can now be made to the following description,
taken in conjunction with the accompanying drawings, in which:
Figure 1.a is a first part of a nodal operation and signal flow diagram
illustrating a complex prior art method for performing a dormant hand-off for
a
mobile node;
Figure 1.b is a second part of the nodal operation and signal flow diagram
illustrating a complex prior art method for performing a dormant hand-off for
a
mobile node; and
Figure 2 is a nodal operation and signal flow diagram illustrative of the
exemplary preferred embodiment of the invention.
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Detailed Description of the Preferred Embodiments
Reference is now made to Figure 2, wherein there is shown a nodal
operation and signal flow diagram illustrative of an exemplary preferred
embodiment of the invention. Shown in Fig. 2 is a CDMA 2000 packet data
cellular telecommunications network 100 comprising at least one Mobile Node
(MN) 110, communicating over an air (radio) interface 112, and via a plurality
of
Base Transceiver Stations (BTSs, not shown) with a plurality of Base Station
Controllers (BSCs), such as for example BSCs 114 and 116. The BSCs 114 and
116 may each comprise a Packet Control Function (PCF), which purpose is to
manage the radio resources of each BTS. The network 100 may further comprise
at least one Mobile Switching Center (MSC) 118 and a plurality of Packet Data
Service Nodes (PDSNs), such as for example PDSN 120 and PDSN 122. The
BSC/PCFs and the PDSNs are connected with each other through an IP-based
network 111. For the purpose of better understanding the present invention, it
is
assumed that a dormant MN 110 moves from a first packet zone, wherein it was
served by BSC/PCF Source (BSC/PCF-S) 114 and PDSN Source (PDSN-S) 120,
to a second packet zone wherein it is to be served by BSS/PCF Target
(BSS/PCF-T) 116 and PDSN Target (PDSN-T) 122. By dormant MN, it is meant
an MN that previously established a Point-to-Point Protocol with a PDSN, such
as for example with the PDSN-S 120, but that did not exchange data over that
connection for a given period of time, thus causing the traffic channel
between
itself and the PDSN 120 to be dropped, while the PPP connection was kept
active in both the MN and the PDSN-S 120.
Therefore, when the MN 110 crosses the packet zone boundary at
dormant state, according to the preferred embodiment of the present invention,
the MN 110 detects a new packet zone identification and sends an origination
request message 124 to the target BSC 116 via a BTS, for requesting service
from BSC/PCF-T 116 of the target packet system. According to the invention,
the
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origination request message 124 may comprise a Packet Zone Identification
parameter 125 indicative of the new packet zone the MN 110 is trying to
register
with, an indication 126 to the effect of that the MN 110 is dormant (no
current data
transfer is taking place), and an identification 127 of the MN 110 itself,
preferably
under the form of an International Mobile Station Identification (IMSI). The
indication 126 may comprise the parameter Data Ready to Sent (DRS) set to zero
(0), DRS=O, that indicates to the network that the MN 110 is dormant since it
sent
no data for a given period of time. Responsive to the receipt of the
origination
request message 124, the BSC/PCF-T 116 replies back to the MN 110 through a
BS acknowledgement order message 129 for confirming the receipt of message
124. The BSC/PCF-T 116 may further exchange with the serving MSC 118
serving set up messages 128 and 130, through which the MSC 118 requests
support of radio resources for the MN 110. In the present scenario, since the
MN
110 has moved to a new packet zone, the BSC/PCF-T 116 selects a new PDSN,
such as the target PDSN (PDSN-T) 122 for providing mobile IP service for the
MN
110, and thus sends an A11 registration request message 132 to the PDSN-T 122
for requesting the set up of an A10 connection (also called herein a Radio
network
Packet data serving node session or connection, (RP) with the MN 110.
According to the preferred embodiment of the present invention, the A11
2 o registration request message 132 comprises first an identification of the
MN 110,
such as for example the IMSI 127, and an indication parameter 134 informing
the
target PDSN 122 that a dormant hand-off is being performed for the MN 110. The
indication parameter 134 may comprise a Data Ready to Sent (DRS) parameter
set to zero (0), DRS=O, for providing that information, or alternatively any
other
Mobility Event Indicator (MEI). Responsive to the receipt of the A11
registration
request message 132, and based on the MN's IMSI 70, the PDSN-T 122 realises
that it has no bindings for the MN 110 (no information characterizing a PPP
connection is found in the PDSN for that MN), and thus deduct that it supports
no
current PPP connection for the MN 110, action 135, and replies back to the
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BSC/PCF-T 116 with an All registration reply message 136 requesting the
establishment of a traffic channel. According to the preferred embodiment of
the
invention, the A11 registration reply message 136 may comprise an acceptance
parameter 138 informing the target BSC 116 that the target PDSN 122 is to
provide mobile IP service for the MN 110, and an indication 140 that the PDSN-
T
122 has data ready to be sent to the MN 110. The indication 140 may comprise a
PDSN_DRS parameter 140, that according to the preferred embodiment of the
invention is now set to 1(PDSN_DRS=1) for requesting the BSC/PCF 116 to set
up the traffic channel and to inform BSC/PCF 116 that the PDSN 122 has data
ready to be sent for the MN 110. Altematively, the indication 140 may be any
Data
Available Indicator (DEI), as believed appropriate by the requirements or
preferences of any network operator. According to the invention, upon receipt
of
the A11 registration reply message 136 having the indicator 140, the BSC/PCF-T
116 proceeds with the establishment of a traffic channel with the MN 110,
action
142. The set-up of the traffic channel may be performed according to the
standard
IOS, lnteroperability Standard for the Access network V.4.0 (or later)
Verification
and Validation (V&V), herein included by reference and referred to as the
Standard.
One the traffic channel 144 is established, the BSC/PCF 116 reports to the
PDSN-T 122 the successful establishment of the traffic channel through a
Registration message 145 that may comprise an Active Start parameter 146.
Thereafter, the BSC/PCF-T 116 replies back to the MSC 118 with an
assignment complete message 143 for confirming the establishment of the
traffic
channel 144.
Immediately following the receipt of the Registration message 145, , the
PDSN-T 122 may begin sending data packets intended for the MN 110. For
example, the first data packets sent from the PDSN 122 to the MN 110 may
comprise Link Layer Protocol (LCP) packets 147 that are used by the BSC/PCF-T
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116 and the MN 110 to establish the new PPP session between the serving PDSN
122 and the MN 110.
The method continues with signalling messages being exchanged between
the PDSN-T 122 and the MN 110 for the establishment of the PPP connection,
action 148, as described for example in the Standard. Once the new PPP
connection 150 is successfully established between the PDSN 122 and the MN
110, traffic data packets, such as for voice and data communications, may be
exchanged between the PDSN-T 122 and the MN 110.
The present invention provides an significant simplification of the prior art
method for dormant handoff by eliminating the need for paging-associated
signalling when a dormant MN enters a new packet zone.
Although several preferred embodiments of the method and system of the
present invention have been illustrated in the accompanying Drawings and
described in the foregoing Detailed Description, it will be understood that
the
invention is not limited to the embodiments disclosed, but is capable of
numerous
rearrangements, modifications and substitutions without departing from the
spirit of
the invention as set forth and defined by the following claims.
