U.S. patent application number 13/230221 was filed with the patent office on 2011-12-29 for method and system for implementing inter-access networks handoff in active state in hrpd network.
This patent application is currently assigned to HUAWEI TECHNOLOGIES CO., LTD.. Invention is credited to Quanzhong Gao, Qingrong He, Zhiming Li.
Application Number | 20110317668 13/230221 |
Document ID | / |
Family ID | 37430935 |
Filed Date | 2011-12-29 |
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United States Patent
Application |
20110317668 |
Kind Code |
A1 |
Gao; Quanzhong ; et
al. |
December 29, 2011 |
Method and System for Implementing Inter-Access Networks Handoff in
Active State in HRPD Network
Abstract
A method and system for implementing an inter-Access Network
(AN) handoff in an active state in a High Rate Packet Data (HRPD)
Network are disclosed. The method includes determining that an
inter-AN handoff operation is necessary and initiating a handoff
procedure to perform the inter-AN handoff, sending data to be
transmitted to an access terminal to the destination AN in advance
in the handoff procedure, and then sending the access terminal the
data to be transmitted to the access terminal by the source AN or
the destination AN according to the result of the handoff
procedure.
Inventors: |
Gao; Quanzhong; (San Diego,
CA) ; He; Qingrong; (Shenzhen, CN) ; Li;
Zhiming; (Schaumburg, IL) |
Assignee: |
HUAWEI TECHNOLOGIES CO.,
LTD.
Shenzhen
CN
|
Family ID: |
37430935 |
Appl. No.: |
13/230221 |
Filed: |
September 12, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11941283 |
Nov 16, 2007 |
8054801 |
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13230221 |
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PCT/CN2006/000989 |
May 16, 2006 |
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11941283 |
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Current U.S.
Class: |
370/331 |
Current CPC
Class: |
H04W 36/10 20130101;
H04W 36/02 20130101; H04W 36/0066 20130101 |
Class at
Publication: |
370/331 |
International
Class: |
H04W 36/00 20090101
H04W036/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2005 |
CN |
200510072595.2 |
May 19, 2005 |
CN |
200510070971.4 |
Jun 14, 2005 |
CN |
200510077113.2 |
Claims
1. A method for implementing an inter-Access Network (AN) handoff
in an active state in a High Rate Packet Data (HRPD) network, the
method comprising: during a handoff procedure from a source AN to a
destination AN, initiating, by the destination AN, a connection
establishment between the destination AN and a Packet Data Service
Network (PDSN) before an access terminal establishes a connection
with the destination AN; receiving, by the destination AN or a
destination Packet Control Function (PCF), data from the PDSN; and
after the access terminal has established the connection with the
destination AN, sending, by the destination AN or the destination
PCF, the data received from the PDSN to the access terminal.
2. The method according to claim 1, further comprising receiving,
by the destination AN, a handoff request message from the source
AN.
3. The method according to claim 2, wherein initiating the
connection establishment between the destination AN and the PDSN
before the access terminal establishes the connection with the
destination AN comprises: sending, by the destination AN, a
connection establishment request to the destination PCF, and
establishing a connection between the destination PCF and the
destination AN; and registering, by the destination PCF, to the
PDSN, and establishing a connection between the destination PCF and
the PDSN.
4. The method according to claim 2, wherein the data received by
the destination PCF or the destination AN from the PDSN are sent to
the source AN or a source PCF simultaneously.
5. The method according to claim 1, further comprising: sending, by
the destination AN, a handoff complete message to the source AN
when the access terminal can receive data via the destination AN,
to cause the source AN interchange information with the source PCF
to release the connection between the source PCF and the source
AN.
6. The method according to claim 2, wherein after receiving, by the
destination AN, a handoff request message from the source AN, the
method further comprises: sending, by the destination AN, a handoff
reply message to the source AN to make the source AN send a channel
assignment message to the access terminal and interchange
information with a source PCF to disconnect an air interface
connection when receiving a reply from the access terminal, or,
interchange information with the source PCF to disconnect the air
interface connection directly after sending the channel assignment
message without waiting for the reply from the access terminal.
7. The method according to claim 6, wherein after sending, by the
destination AN, the handoff reply message to the source AN to make
the source AN send the channel assignment message to the access
terminal, the method further comprises: allocating, by the
destination AN, a Uni-cast Access Terminal Identifier (UATI), for
the access terminal.
8. The method according to claim 7, wherein the method further
comprises: interchanging, by the destination AN, information with
the destination PCF so as to establish an air interface
connection.
9. A access network (AN), comprising: a first unit, configured to
initiate a connection establishment between the AN and a Packet
Data Service Network (PDSN) before an access terminal establishes a
connection with the AN during handoff procedure from a source AN to
the AN; a second unit, configured to receive data from the PDSN;
and a third unit, configured to send the data received from the
PDSN to the access terminal after the access terminal has
established the connection with the AN.
10. The AN according to claim 9, further comprising: a fourth unit,
configured to receive a handoff request message from the source
AN.
11. The AN according to claim 9, the first unit is configured to
send a connection establishment request to a destination PCF and
establish a connection between the destination PCF and the AN to
make the destination PCF establish a connection between the
destination PCF and the PDSN.
12. The AN according to claim 10, further comprising: a fifth unit,
configured to send a handoff complete message to the source AN when
the access terminal can receive data via the AN, to make the source
AN interchange information with the source PCF to release the
connection between a source PCF and the source AN.
13. The AN according to claim 9, further comprising: a sixth unit,
configured to allocate a Uni-cast Access Terminal Identifier (UATI)
for the access terminal.
14. The AN according to claim 9, further comprising: a seventh
unit, configured to interchange information with a destination PCF
so as to establish an air interface connection.
Description
[0001] The present application is a continuation of U.S.
application Ser. No. 11/941,283, filed Nov. 16, 2007, which is a
continuation of International Application No. PCT/CN2006/000989,
filed May 16, 2006, which claims priority to Chinese Application
No. 200510072595.2, filed May 16, 2005, Chinese Application No.
200510070971.4, filed May 19, 2005, and Chinese Application No.
200510077113.2, filed Jun. 14, 2005, each of which is incorporated
herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to the field of
communications, and in particular, to a method and system for
implementing an inter-Access Network (AN) handoff in an active
state in a High Rate Packet Data (HRPD) network.
BACKGROUND
[0003] With the development of communication technologies, the 3rd
Generation Partnership Project 2 (3GPP2) proposed a standard for
HRPD technology in order to solve the crucial issue on air
interfaces in a Code Division Multiple Access (CDMA) system. This
standard aims to improve the data transmission rate on a wireless
interface. Compared with the data rate of 153.6 kbit/s provided by
CDMA 2000 1x, the HRPD technology may provide a forward data rate
up to 2.4 Mbit/s.
[0004] In an HRPD network, a new modulation technique is utilized
over air interface and methods for data rate control, scheduling
optimization and time division multiplex and the like are added,
which cause a significant improvement in data transmission rate
over air interface. In the HRPD technology, a private data channel
on a CDMA carrier (1.25 MHz) may be employed to support high rate
packet data services, with a forward data rate up to 2.4576 Mbit/s,
and a peak data rate of 153.6 kbit/s for a single user supported in
reverse direction.
[0005] A separate carrier is needed to support HRPD when deploying
an HRPD network. In this manner, when moving in the HRPD network,
an access terminal may move from one AN into another AN in the HRPD
network. At this time, a handoff from a source NA to a destination
NA is necessary.
[0006] Currently, the 3GPP2 standard supports only the inter-AN
handoff in dormant state. This handoff process is as follows: when
an access terminal performing a data service in an HRPD network
moves to an edge of the coverage zone of a cell, it is necessary to
be handed off to another AN so as to continue its data service. At
this time, the system switches the packet data service from an
active state to a dormant state at the source AN, and then hands
off to the destination AN in the dormant state. After moving into
the destination AN, the system switches the packet data service
from the dormant state back to the active state at the destination
AN.
[0007] With the above handoff process, a handoff operation from a
source AN to a destination AN may be implemented. However, for a
data service with high real-time requirement, such as Voice over IP
(VoIP), Video Phone, Push-To-Talk (PTT) and stream media, such a
handoff process may cause an interruption of the service, which
will result in an adverse effect to the utilization of the service
for the user.
[0008] In other words, in the method of inter-AN, inter-Packet
Control Function (PCF) handoff in dormant state provided in the
prior art standard, it is necessary to release the Point-to-Point
Protocol (PPP) connection being in use during a handoff process,
and thus it is necessary for a Packet Data Service Network (PDSN)
to reallocate a new PPP connection for the destination network.
During the reallocation of the new PPP connection, for one thing,
the service of the user may be interrupted due to the failure of
the reallocation process resulted from problems of the resources;
for another, the current service of the user may be delayed
significantly because it will cost the PDSN some time to
reestablish a PPP connection.
[0009] In view of this, a hard handoff process is required to
ensure the continuity of a service during an inter-AN handoff
process. However, in the prior art standard, only an inter-AN
handoff process in dormant state is defined, and there is a lack of
an inter-AN, inter-PCF hard handoff process in an active state in
an HRPD system.
SUMMARY OF THE INVENTION
[0010] In view of the above, the present invention is to provide a
method and system for implementing an inter-AN handoff in an active
state in an HRPD network, to ensure the continuity of a service for
an access terminal during a handoff process across ANs, across
PCFs.
[0011] Based on this, the present invention provides a method to
ensure the returnablity in the case of a failure of a handoff, so
as to improve the reliability of the service communication.
[0012] The present invention provides the following technical
solutions.
[0013] A method for implementing an inter-AN handoff in an active
state in an HRPD network is provided, which includes the following
steps. It is determined that an inter-AN handoff operation is
necessary, and a handoff procedure is initiated. In the inter-AN
handoff procedure, a connection between a destination AN and a PDSN
is established before an access terminal establishes a connection
with the destination AN, and user data is sent by the PDSN to the
destination AN/PCF. When the access terminal establishes a
connection with the destination AN, the data received from the PDSN
is sent from the destination AN/PCF to the access terminal.
[0014] Here, determining that the inter-AN handoff operation is
necessary and initiating the handoff procedure includes the
following steps. A source AN determines that an inter-AN handoff
operation is necessary according to a received route update
message, and determines the destination AN corresponding to the
source AN. The source AN sends a handoff request message to the
destination AN.
[0015] Here, when a handoff is performed between Access Networks
belonging to different PCFs, establishing the connection and
sending the user data includes the following steps. In response to
receiving the handoff request sent from the source AN, the
destination AN sends a connection establish request to the
destination PCF, and establishes a connection between the
destination PCF and the destination AN; the destination PCF
registers to the PDSN, and establishes a connection between the
destination PCF and the PDSN. When a source PCF requests to stop
sending data, the PDSN sends data to the destination PCF and stops
sending data to the source PCF.
[0016] This last step could include the following steps. When
disconnecting of an air interface connection between the source AN
and the access terminal is determined, the source PCF sends a
stop-sending-data request to the PDSN requesting the PDSN to stop
sending data the source PCF. When receiving the stop-sending-data
request sent from the source PCF, the PDSN starts sending data to
the destination PCF if the PDSN has not sent data to the
destination PCF, while stopping sending data to the source PCF.
[0017] Here, when a handoff is performed between Access Networks
belonging to different PCFs, establishing the connection between
the destination AN and PDSN and sending the user data includes the
following steps. In response to receiving the handoff request sent
from the source AN, the destination AN sends a connection establish
request to the destination PCF, and establishes a connection
between the destination PCF and the destination AN. The destination
PCF registers to the PDSN, and establishes a connection between the
destination PCF and the PDSN. After the connection between the
destination PCF and the PDSN has been established, the PDSN sends a
bi-cast indication message to the source AN to notify the source
AN/PCF that the PDSN will send data to the destination PCF/AN and
the source AN/PCF simultaneously.
[0018] When the existing connection between the PCF and the PDSN is
determined as an inter-AN handoff, the PDSN sends the bi-cast
indication message. Here, the data includes real-time service data
and non-real-time service data. Here, the method further includes
in response to receiving the bi-cast Indication message, the source
AN stops sending real-time service packets while continuing to send
non-real-time service packets.
[0019] Here, the method further includes that when the access
terminal can receive data via the destination AN, the destination
AN sends a handoff complete message to the source AN, and that in
response to receiving the handoff complete message, the source AN
interchanges information with the source PCF, and releases the
connection between the source PCF and the source AN.
[0020] Here, establishing the connection and sending the user data
further includes the following step. The source AN sends a channel
assignment message to the access terminal according to a handoff
reply message sent from the destination AN, and interchanges
information with the source PCF instructing to disconnect an air
interface connection when receiving a reply from the access
terminal, or, the source AN interchanges information with the
source PCF instructing to disconnect the air interface connection
directly after sending the channel assignment message without
waiting for the replay from the access terminal.
[0021] For example, the source AN sends the channel assignment
message to the access terminal, the access terminal is handed off
to the destination AN, and the destination AN allocates a Uni-cast
Access Terminal Identifier (UATI) for the access terminal, so as to
complete assignment of the UATI. The destination AN interchanges
information with the destination PCF so as to establish an air
interface connection of the destination AN.
[0022] Alternatively, the source AN sends a UATI assignment message
to the access terminal, and sends the traffic channel assignment
message to the access terminal when the UATI assignment is
completed, and completes the channel assignment. The destination AN
interchanges information with the destination PCF so as to
establish an air interface connection of the destination AN.
[0023] Here, for a handoff between Access Networks belonging to
different PCFs, the PDSN sends data to be transmitted to the access
terminal simultaneously to the source PCF to which the source AN
belongs and the destination PCF to which the destination AN
belongs.
[0024] Here, the data to be transmitted to the access terminal is
saved in the Base Transceiver Stations corresponding to the source
AN and the destination AN respectively.
[0025] Here, the method further includes that when the handoff
procedure from the source AN to the destination AN fails, the
source AN and the source PCF send the access terminal the data to
be transmitted to the access terminal.
[0026] The present invention further provides a system for
implementing an inter-AN handoff in an active state in an HRPD
network, including a source AN, a source PCF, a destination AN, and
a destination PCF.
[0027] After the source AN initiates an inter-AN handoff procedure,
the destination AN establishes a connection with a PDSN before an
access terminal establishes a connection with the destination AN,
and the PDSN sends user data to the destination AN/PCF.
[0028] After the access terminal has established the connection
with the destination AN, the destination AN/PCF sends the data
received from the PDSN to the access terminal.
[0029] Here, when the source PCF requests to stop sending data, the
PDSN sends data to the destination PCF while stopping sending data
to the source PCF.
[0030] Here, after the connection between the destination PCF and
the PDSN has been established, the PDSN sends a bi-cast indication
message to the source AN to notify the source AN/PCF that the PDSN
will send data to the destination PCF/AN and the source AN/PCF
simultaneously.
[0031] As can be seen from the technical solutions provided in the
present invention, an inter-AN, inter-PCF hard handoff is achieved.
During the procedure for such a hard handoff, the PDSN sends data
to the destination PCF/AN in advance, so that the data may be sent
from the destination PCF/AN to the access terminal immediately
after a connection between the access terminal and the destination
AN has been established. Accordingly, the continuity of a service
may be improved, and the time delay and the packet loss due to a
time delay may be reduced.
[0032] Furthermore, if the handoff fails, the data may be sent to
the access terminal by the source PCF, so that the packet loss
resulted from the failed handoff may be avoided.
[0033] Alternatively, after a connection between the destination
PCF/AN and the PDSN has been established, the PDSN may send a
concurrent indication message to the source PCF/AN, and sends data
to the destination PCF and the source PCF simultaneously when
receiving a reply from the source PCF/AN, then the destination PCF
buffers the data in the handoff procedure. The source PCF also
buffers the data after receiving a bi-cast indication message for a
future return in the case of a handoff failure. Therefore, the
reliability may be improved. The destination AN or PCF may send
data to the access terminal immediately after the establishment of
a connection between the access terminal and the destination
AN.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a schematic diagram illustrating the networking
structure of an HRPD network according to the present
invention;
[0035] FIG. 2 is a flow chart illustrating an inter-PCF, inter-AN
hard handoff in a method according to an embodiment of the present
invention; and
[0036] FIG. 3 is a flow chart illustrating an inter-PCF, inter-AN
hard handoff in a method according to another embodiment of the
present invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0037] The essence of the present invention lies in that,
respective data information is sent to a destination AN in advance
during an inter-AN handoff. The data may be saved on the
destination AN, or may be saved on a PCF to which the destination
AN belongs, or may be saved on a Base Transceiver Station (BTS) to
which the destination AN corresponds. Therefore, the continuity of
a service after the handoff process ends may be ensured. Meanwhile,
the data may be sent to the source AN/PCF, and saved at the source
AMN/PCF, or saved on a Base Transceiver Station (BTS) to which the
source AN corresponds. In this manner, the continuity of a service
may be guaranteed whether the handoff is successful or not. Here,
the access terminal may be a Mobile Station (MS) or the like.
[0038] The networking structure of an HRPD network is generally
shown in FIG. 1. In the HRPD network, an Access Terminal (AT) 110
interworks with a source AN 120 through an air interface AL, the
source AN 120 interworks with a PCF 130 via interfaces A8 and A9,
the PCF 130 interworks with a PDSN 140 via interfaces A10 and A11.
In this manner, the AT 110 may obtain the data traffic sent from
the PDSN 140 via the source AN 120 and the PCF 130.
[0039] In the implementation, an method according to the present
invention mainly includes the following.
[0040] When a destination AN establishes an A8 connection with a
destination PCF and the destination PCF establishes an A10
connection with a PDSN (the A10 connection is a connection between
a PCF and a PDSN) during an inter-PCF, inter-AN hard handoff
process, the PDSN determines on its own accord whether to send a
bi-cast indication message according as whether there exists an A10
connection.
[0041] During the inter-PCF handoff, after the A8 and A10 have been
established between the destination AN, the destination PCF and the
PDSN, the PDSN sends data to both the source PCF and the
destination PCF, so as to reduce the delay and packet loss of the
destination AN/PCF. Further, the PDSN notifies the source PCF
before sending data, and the destination AN/PCF may receive the
subsequent data when receiving the notification. The source AN/PCF
will not send the subsequently received data to the access terminal
if the handoff is successful, and will continue to send the data
that are not overtime only when the handoff fails.
[0042] Or, a method according to the present invention may include
the following.
[0043] After sending a traffic channel assignment message to (or
receiving a response to this message from) an access terminal, a
source AN requests a PDSN to stop sending traffic data to a source
PCF and send traffic data in advance to a destination PCF.
[0044] In the above process according to the present invention, the
PDSN may decide according to the service options to send data to
the destination PCF while sending data to the source PCF for a
delay-sensitive service. In other words, if the requirement for
delay is in accord with a predetermined requirement, after the A8
and A10 has been established between the destination AN, the
destination PCF and the PDSN during an inter-PCF handoff.
[0045] Furthermore, in the method according to the present
invention, the data received by the destination AN may be sent
directly to a BTS in the destination AN for buffering, and the data
received by the source AN may also be sent to a BTS in the source
AN for buffering so as to reduce delay during an inter-AN
handoff.
[0046] Upon receiving a channel assignment complete message or a
UATI complete message from the access terminal, the destination AN
sends data to the access terminal immediately.
[0047] In the technical solution shown in FIG. 2, after sending the
traffic channel assignment message to the access terminal, the
source PCF may choose to send an Xoff (stop sending data) message
to the PDSN requesting the PDSN to stop sending data so as to save
the bandwidth (see step 214). Alternatively, the source PCF may
choose not to send the Xoff message so as to facilitate the return
in the case of a handoff failure.
[0048] With the method according to the present invention, the
requirement of the transmission of a real-time service and a
non-real-time service in a HRPD network could be met.
[0049] In an actual application, an embodiment of the present
invention provides a process for an inter-AN hard handoff in the
case of inter-PCF, i.e., a process for an inter-AN hard handoff
between different PCFs, which will be described below.
[0050] A process for an Inter-AN/Inter-PCF hard handoff, i.e., an
inter-AN hard handoff between different PCFs, is as shown in FIG. 2
which includes the following steps.
[0051] Step 21: An AT sends a source AN a route update message
which contains the information of neighboring area in which the
signal is stronger.
[0052] Step 22: The source AN determines that a hard handoff is
necessary according to the route update message, and sends a
destination AN a handoff request message which contains the
information of a session related with the AT.
[0053] Step 23: On receiving the handoff request message, the
destination AN verifies the message and authenticates the AT. If
the verification is passed, the destination AN establishes an A8
connection with a destination PCF and starts a timer TA8-Setup.
Here, an indication requesting the PDSN to send data to the
destination PCF in advance may be added in the message for
establishing the A8.
[0054] Step 24: On receiving an A9-Setup-A8 message, the
destination PCF initiates an A10 connection establishment to the
PDSN, i.e., sends a registration request message to the PDSN
requesting the PDSN to send data to the destination PCF in advance.
A new message may be added to send the indication.
[0055] Step 25: After the A10 connection has been established, the
PDSN responds to the destination PCF by sending an A11 registration
reply message, i.e. an A11-registration Reply message.
[0056] Step 26: After the A8 connection has been completed, the
destination PCF feeds back an establishment of A9 and A8 interfaces
connection message, i.e., an A9-Connect-A8 message, to the
destination AN. The destination AN then stops the timer
TA8-Setup.
[0057] Step 27: The PDSN sends a bi-cast Indication message to the
source PCF indicating that the data will be sent by PDSN to the
destination AN/PCF and the source AN/PCF at the same time.
[0058] Step 28: After receiving the bi-cast Indication message, the
source PCF sends the bi-cast Indication message to the source AN
notifying the source AN to continue to receive data from the source
PCF. After receiving the bi-cast Indication message, the source AN
needs to continue to send the received non-real-time traffic data
to the access terminal. As for the real-time traffic data, the
source AN needs to send only the data which is received before the
reception of the bi-cast Indication message to the access terminal.
The source AN will not send the data which is received after the
reception of the bi-cast Indication message to the access terminal
unless the handoff fails.
[0059] In other words, after determining that the bi-cast
Indication message has been received, for the data packets which
are received after the reception of the bi-cast Indication message,
the source AN will not send the real-time traffic data packets to
the access terminal, but will continue to send the non-real-time
traffic data packets to the access terminal.
[0060] In addition, in this step, a reply-to-PDSN mechanism may be
chosen, and a reply mechanism may also be added between the PCF and
AN, so as to ensure the reliability of the signaling
transmission.
[0061] Step 29: After sending the bi-cast Indication message, the
PDSN may decide whether to send forward data to the destination PCF
according to the attributes of traffic, or may send forward data to
the destination PCF uniformly regardless of the attributes of
traffic. The destination PCF saves the received data and sends the
received data to the access terminal immediately after the
destination AN establishes a connection with the access
terminal.
[0062] Step 210: After sending the bi-cast Indication message, the
PDSN sends forward data to the source PCF at the same time. The
data may be saved at the source PCF, or may be sent to the source
AN and saved at the source AN.
[0063] Step 211: The destination AN sends the source AN a handoff
request reply message which contains the parameters of the channel
assigned to the destination AN and the like.
[0064] Step 215: After receiving the handoff request reply message,
the source AN sends a channel assignment message over the traffic
channel to the AT instructing the AT to perform a handoff to the
destination AN.
[0065] Step 212: At the same time, the source AN sends the source
PCF a message requesting the disconnection between the A9 and AL
interfaces, i.e. an A9-AL-Disconnected message, instructing the
source PCF to stop sending data to the source AN. In other words,
the source AN will not wait a reply to the traffic channel
assignment message, but directly sends the source PCF a message
requesting the disconnection between the A9 and AL interfaces,
i.e., an A9-AL-Disconnected message, instructing the source PCF to
stop sending data to the source AN.
[0066] Alternatively, after receiving a reply to the traffic
channel assignment message, the source AN sends the source PCF a
message requesting the disconnection between the A9 and AL
interfaces, i.e., an A9-AL-Disconnected message, instructing the
source PCF to stop sending data to the source AN.
[0067] Step 213: In response to the message requesting the
disconnection between the A9 and AL interfaces, the source PCF
sends the source AN an acknowledge message, i.e., an
A9-A1-Disconnected Ack message, and stops sending data to the
source AN.
[0068] Step 214: The source PCF sends the PDSN an Xoff message,
i.e., a stop sending data message, requesting the PDSN to stop
sending data to the source PCF, and indicating the handoff has been
performed.
[0069] This step is optional. If this message is sent, the
communication resources of the A interface may be saved. If this
message is not sent, it may be ensured not to loss data in the case
of a failure of the handoff though the communication resources of
the A interface may be occupied.
[0070] Step 216: When being handed off to the destination AN, the
AT sends a channel assignment complete message to the destination
AN.
[0071] Step 217: The destination AN sends a UATI assignment message
to the AT over the traffic channel, to allocate a new UATI for the
AT.
[0072] Step 218: Upon receipt, the AT sends a UATI complete message
back to the destination AN over the traffic channel.
[0073] Step 219: After the handoff is successful, a session between
the AT and the PDSN is activated, and the destination AN sends data
to the AT.
[0074] This step may be executed at any moment after the execution
of step 218, the sooner, the better.
[0075] Step 220: The destination AN sends an A9-AL Connected
message indicating the channel has been activated.
[0076] Step 221: The destination PCF sends a registration message,
i.e. an A11-Registration Request message, to the PDSN, indicating
that the link has been activated, and the PDSN sends a registration
reply back to the destination PCF.
[0077] If step 214 is not executed or the Xoff message is lost, the
PDSN will stop sending data to the source AN/PCF at this
moment.
[0078] Step 222: The destination PCF sends back an acknowledge
message of the connection between the A9 and the AL, i.e. an
A9-AL-Connected Ack message, to the destination AN.
[0079] Step 223: The destination AN sends a handoff complete
message to the source AN.
[0080] Step 224: After receiving the handoff complete message, the
source AN sends an A9-Release-A8 message to the source PCF
notifying the source PCF to release the connection between the A9
and A8 interfaces. At the same time, a timer TAre19 is started, and
the A8 link is released at the source AN.
[0081] Step 225: After receiving the A9-Release-A8 message from the
source AN, the source PCF sends an A11-Registration Request message
to the PDSN to release the A10 connection. After releasing the A10
connection, the PDSN sends back an A11-Registration Reply message
to the source PCF, and the source PCF releases the resources of the
A10 connection.
[0082] Step 226: The source CF releases the resources of the A8
connection, and sends the source AN an A9-Release-A8 Complete
message (indicating that the connection between the A9 and A8 has
been released), and the source AN will stop the timer TAre19 on
receiving the message.
[0083] Steps 215, 216, 217 and 218 described above with reference
to FIG. 2 may alternatively be implemented by the following
steps.
[0084] After step 211 described above, step 215' may be
executed.
[0085] Step 215': The source AN sends a UATI assignment message to
the AT over the traffic channel to allocate a new UATI to the AT.
This new UATI is allocated by the destination AN, and may be
carried to the source AN via a handoff request reply message.
[0086] Step 216': The AT sends a UATI complete message back to the
source AN over the traffic channel.
[0087] Step 217': The source AN sends a channel assignment message
to the AT over the traffic channel, so as to perform the handoff to
the destination AN.
[0088] The step 212 may be executed directly subsequent to step
217', or may be executed after receiving a channel assignment reply
message returned from the AT.
[0089] After step 214, step 218' will be executed.
[0090] Step 218': After being handed off to the destination AN, the
AT sends a channel assignment complete message to the destination
AN over the access channel.
[0091] In an actual application, the above two processes may be
chosen as required.
[0092] The present invention provides another process for an
Inter-AN/Inter-PCF hard handoff as shown in FIG. 3 which includes
the following steps.
[0093] Step 31: An AT sends a source AN a route update message
which contains the information of neighboring area in which the
signal is stronger.
[0094] Step 32: The source AN determines that a hard handoff is
necessary according to the route update message, and sends a
destination AN a handoff request message which contains the
information of a session related with the AT.
[0095] Step 33: On receiving the handoff request message, the
destination AN verifies the message and authenticates the AT. If
the verification is passed, the destination AN establishes an A8
connection with a destination PCF and starts a timer TA8-Setup.
[0096] Step 34: On receiving an A9-Setup-A8 message, the
destination PCF initiates an A10 connection establishment to the
PDSN, in other words, sends a registration message to the PDSN.
[0097] Step 35: After the A10 connection has been established, the
PDSN responds to the destination PCF by sending an A11-registration
Reply message.
[0098] Step 36: After the A8 connection is completed, the
destination PCF feeds back an A9-Connect-A8 message to the
destination AN. The destination AN then stops the timer
TA8-Setup.
[0099] Step 37: The destination AN sends the source AN a handoff
request reply message which contains the parameters of the channel
assigned to the destination AN and the like.
[0100] After receiving the handoff request reply message, the
source AN executes step 312 to assign the traffic channel. At the
same time, step 38 is executed to release the connection between
the A9 and AL. Of course, step 38 may also be executed after
receiving a channel assignment reply message returned from the
AT.
[0101] Step 38: The source AN sends an A9-AL-Disconnected message
(disconnect the connection between the A9 and AL) to the source
PCF, notifying the source PCF to stop sending data to the source
AN.
[0102] Step 39: The source PCF returns an A9-AL-Disconnected Ack
(acknowledging the disconnection between the A9 and AL) message to
the source AN, and stops sending data to the source AN.
[0103] Step 310: The source PCF sends the PDSN an Xoff message,
i.e., a stop sending data message, requesting the PDSN to stop
sending data to the source PCF, and indicating the handoff has been
performed.
[0104] Step 311: After receiving the message, the PDSN stops
sending data to the source AN, and sends data to the destination
PCF, wherein the data may be sent to the destination AN.
[0105] Step 312: The source AN sends a channel assignment message
to the AT over the traffic channel, instructing the AT to be handed
off to the destination AN.
[0106] The AT may return a reply of this message to the source AN
to confirm the completion of the assignment. However, this
operation of returning a reply by the AT is optional, and is not a
necessary step.
[0107] Step 313: When being handed off to the destination AN, the
AT sends a channel assignment complete message to the destination
AN over the access channel.
[0108] Step 314: The destination AN sends an UATI assignment
message to the AT over the access channel, to allocate a new UATI
for the AT.
[0109] Step 315: Upon receipt, the AT sends an UATI complete
message back to the destination AN over the traffic channel.
[0110] Step 316: After the handoff is successful, a session between
the AT such as a mobile terminal (MS) and the PDSN is activated.
That is, the access terminal may receive data via the destination
AN.
[0111] This step may be executed at any moment after the execution
of step 314, the sooner, the better.
[0112] Step 317: The destination AN sends the destination PCF a
message to establish a connection between the A9 and AL interfaces,
i.e., an A9-AL Connected message indicating the channel has been
activated.
[0113] Step 318: The destination PCF sends an A11-Registration
Request message to the PDSN, indicating the link has been
activated, and the PDSN sends a registration reply message back to
the destination PCF.
[0114] Step 319: The destination PCF sends back an A9-AL-Connected
Ack message (an acknowledgment to the A9-AL connection) to the
destination AN.
[0115] Step 320: The destination AN sends a handoff complete
message to the source AN.
[0116] Step 321: After receiving the handoff complete message, the
source AN sends an A9-Release-A8 message (releasing the connection
between the A9 and A8) to the source PCF, and starts a timer TAre19
locally, and releases the A8 link.
[0117] Step 322: After receiving the A9-Release-A8 message from the
source AN, the source PCF sends an A11-Registration Request message
to the PDSN requesting to release the A10 connection. After
releasing the A10 connection, the PDSN sends back an
A11-Registration Reply message to the source PCF, and the source
PCF releases the resources of the A10 connection.
[0118] Step 323: After releasing the resources of the A8
connection, the source PCF sends the source AN an A9-Release-A8
Complete message (indicating that the connection between the A9 and
A8 has been released), and the source AN stops the timer
TAre19.
[0119] Steps 312, 313, 314 and 315 described above with reference
to FIG. 3 may alternatively be implemented by the following
steps.
[0120] After step 37 described above, step 312' may be
executed.
[0121] Step 312': The source AN sends an UATI assignment message to
the AT over the traffic channel to allocate a new UATI to the AT.
This new UATI is allocated by the destination AN, and may be
carried to the source AN via a handoff request reply message.
[0122] Step 313': The AT sends an UATI assignment complete message
back to the source AN over the traffic channel.
[0123] Step 314': The source AN sends a channel assignment message
to the AT over the traffic channel, so as to perform the handoff to
the destination AN.
[0124] Step 38 may be executed directly subsequent to step 314', or
may be executed after receiving a channel assignment reply message
returned from the AT.
[0125] After step 38, step 315' will be executed.
[0126] Step 315': After being handed off to the destination AN, the
AT sends a channel assignment complete message to the destination
AN over the access channel.
[0127] In an actual application, the above two processes may be
chosen as required.
[0128] The steps shown in FIG. 2 and FIG. 3 should not be limited
to the exact order for execution described above, and some of the
steps may be executed at a time according to actual requirement.
For example, step 222 in FIG. 2 and step 319 in FIG. 3 need only to
be executed after the channel and UATI assignment for the AT has
been completed, and are not limited to be executed after the
connection between A9 and AL is established. For another example,
the channel and UATI assignment as shown in FIG. 2 and FIG. 3 may
be executed at any time after acknowledging that a connection
between the destination AN and PDSN has been established, and is
not necessarily be limited to the processing order as shown in FIG.
2 and FIG. 3.
[0129] In summary, with the method according to the embodiments of
the present invention, an inter-PCF, inter-AN hard handoff may be
implemented, and a handoff mechanism in an HRPD network with less
packet loss and higher reliability is provided.
[0130] Further, as can be seen from the above description of the
method according to the embodiments of the present invention, a
system for an inter-AN handoff in an active state in an HRPD
network is also provided. The system includes a source AN, a source
PCF, a destination AN, a destination PCF and a PDSN. After the
source AN initiates an inter-AN handoff, and before the access
terminal establishes a connection with the destination AN, the
destination AN establishes a connection with the PDSN, and the PDSN
sends user data to the destination AN/PCF. When the access terminal
establishes a connection with the destination AN, the destination
AN/PCF sends the data received from the PDSN to the access
terminal.
[0131] Here, the PDSN sends data to the destination PCF and stops
sending data to the source PCF when the source PCF requests the
PSDN to stop sending data. Or, after the connection between the
destination PCF and the PDSN has been established, the PDSN sends a
bi-cast Indication message to the source AN notifying the source
AN/PCF that the PDSN will send data to the destination PCF/AN and
the source AN/PCF at the same time.
[0132] The present invention has been described and illustrated by
the embodiments of the present invention and the drawings. It shall
be recognized by those skilled in the art that those embodiments
and drawings are merely illustrative and not restrictive, that the
present invention shall not be limited to those embodiments and
drawings and that various modifications and variations can be made
to the embodiments of the present invention in light of the
descriptions and the drawings without departing from the spirit and
scope of the present invention as defined by the accompanying
claims.
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