U.S. patent application number 14/540579 was filed with the patent office on 2015-03-12 for l2 tunneling based low latency single radio handoffs.
This patent application is currently assigned to INTEL CORPORATION. The applicant listed for this patent is Intel Corporation. Invention is credited to Vivek Gupta, Pouya Taaghol.
Application Number | 20150071251 14/540579 |
Document ID | / |
Family ID | 41725347 |
Filed Date | 2015-03-12 |
United States Patent
Application |
20150071251 |
Kind Code |
A1 |
Gupta; Vivek ; et
al. |
March 12, 2015 |
L2 TUNNELING BASED LOW LATENCY SINGLE RADIO HANDOFFS
Abstract
An example of this invention provides low latency handovers
between Mobile WiMAX and 2G/3G/LTE networks with only a single
radio transmitting at any given point in time, by establishing L2
tunnel between 3GPP MME and WiMAX ASN for control plane signaling
to perform pre-registration, pre-authentication and context
transfer to the target network, while UE maintains its connection
to the source network, and by setting up bearer path for packet
forwarding between Servicing Gateway and WiMAX ASN. An example of
this invention uses a virtual eNB to facilitate low latency L2
handoffs to legacy 2G/3G networks with minimum impact to SGSN and
MME.
Inventors: |
Gupta; Vivek; (San Jose,
CA) ; Taaghol; Pouya; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Intel Corporation |
Santa Clara |
CA |
US |
|
|
Assignee: |
INTEL CORPORATION
Santa Clara
CA
|
Family ID: |
41725347 |
Appl. No.: |
14/540579 |
Filed: |
November 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12204075 |
Sep 4, 2008 |
8891441 |
|
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14540579 |
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Current U.S.
Class: |
370/331 |
Current CPC
Class: |
H04W 36/14 20130101;
H04W 36/0011 20130101 |
Class at
Publication: |
370/331 |
International
Class: |
H04W 36/00 20060101
H04W036/00; H04W 36/14 20060101 H04W036/14 |
Claims
1-30. (canceled)
31. A user equipment (UE) to execute an inter-network handover, the
UE being configured to: communicate with a source radio network;
receive a message from the source radio network to initiate a
handover procedure to a target radio network; exchange messages
with the target radio network via the source radio network through
a tunnel established between the source radio network and the
target radio network; and switch from the source radio network to
the target radio network to execute the handover, wherein handover
signaling is tunneled between the UE and the target network via the
tunnel.
32. A user equipment as claimed in claim 31, wherein the tunnel
comprises an S101 interface between the source radio network and
the target radio network.
33. A user equipment as claimed in claim 31, wherein the UE is
further configured to pre-register with a target radio network
prior to executing the handover.
34. A user equipment as claimed in claim 31, wherein the messages
are exchanged inside radio resource control (RRC) messages.
35. A user equipment as claimed in claim 31, wherein the source
radio network comprises a Third Generation Partnership Project
(3GPP) network and the target radio comprises a non-3GPP
network.
36. A user equipment as claimed in claim 31, wherein the target
radio network comprises a Code Division Multiple Access (CDMA)
network.
37. A user equipment as claimed in claim 31, wherein the target
network comprises a high data rate Packet (HDRP) network.
38. A method to execute an inter-network handover, the method
comprising: communicating with a source radio network; receiving a
message from the source radio network to initiate a handover
procedure to the target radio network; exchanging messages with the
target radio network via the source radio network through a tunnel
established between the source radio network and the target radio
network; and switching from the source radio network to the target
radio network to execute the handover, wherein handover signaling
is tunneled between the UE and the target network via the
tunnel.
39. A method equipment as claimed in claim 38, wherein the tunnel
comprises an S101 interface between the source radio network and
the target radio network.
40. A method equipment as claimed in claim 38, wherein the UE is
further configured to pre-register with a target radio network
prior to executing the handover.
41. A method equipment as claimed in claim 38, wherein the messages
are exchanged inside radio resource control (RRC) messages.
42. A method equipment as claimed in claim 38, wherein the source
radio network comprises a Third Generation Partnership Project
(3GPP) network and the target radio comprises a non-3GPP
network.
43. A user equipment as claimed in claim 38, wherein the target
radio network comprises a Code Division Multiple Access (CDMA)
network.
44. A user equipment as claimed in claim 38, wherein the target
network comprises a high data rate Packet (HDRP) network.
45. An enhanced Node B (eNB) to facilitate an inter-network
handover for a user equipment (UE), the eNB being configured to:
couple the UE to a source radio network; send a message to the UE
to initiate a handover procedure to a target radio network;
transfer messages between the UE and the target radio network via
the source radio network through a tunnel established between the
source radio network and the target radio network; and tunnel
handover signals between the UE and the target network via the
tunnel to facilitate the handover of the UE from the source network
to the target network.
46. An enhanced Node B as claimed in claim 45, wherein the tunnel
comprises an S101 interface between the source radio network and
the target radio network.
47. An enhanced Node B as claimed in claim 45, wherein the UE is
further configured to pre-register with a target radio network
prior to executing the handover.
48. An enhanced Node B as claimed in claim 45, wherein the messages
are exchanged inside radio resource control (RRC) messages.
49. An enhanced Node B as claimed in claim 45, wherein the source
radio network comprises a Third Generation Partnership Project
(3GPP) network and the target radio comprises a non-3GPP
network.
50. An enhanced Node B as claimed in claim 45, wherein the target
radio network comprises a Code Division Multiple Access (CDMA)
network.
51. An enhanced Node B as claimed in claim 45, wherein the target
network comprises a high data rate Packet (HDRP) network.
52. A method to execute an inter-network handover, the method
comprising: communicating with a source radio network; receiving a
message from the source radio network to initiate a handover
procedure to the target radio network; exchanging messages with the
target radio network via the source radio network through a tunnel
established between the source radio network and the target radio
network; and switching from the source radio network to the target
radio network to execute the handover, wherein handover signaling
is tunneled between the UE and the target network via the
tunnel.
53. A method as claimed in claim 52, wherein the tunnel comprises
an S101 interface between the source radio network and the target
radio network.
54. A method as claimed in claim 52, wherein the UE is further
configured to pre-register with a target radio network prior to
executing the handover.
55. A method as claimed in claim 52, wherein the messages are
exchanged inside radio resource control (RRC) messages.
56. A method as claimed in claim 52, wherein the source radio
network comprises a Third Generation Partnership Project (3GPP)
network and the target radio comprises a non-3GPP network.
57. A method as claimed in claim 52, wherein the target radio
network comprises a Code Division Multiple Access (CDMA)
network.
58. A method as claimed in claim 52, wherein the target network
comprises a high data rate Packet (HDRP) network.
Description
BACKGROUND OF THE INVENTION
[0001] Mobile service providers already possess and operate several
heterogeneous access technologies and networks. The mixed network
environments are expected to become more prevalent as different
radio technologies best serve different deployment types and
environments. For example, Wi-Fi.TM. has shown to be a great
technology for indoor operation, whereas cellular technologies such
as 2G/3G (2.sup.nd Generation/3.sup.rd Generation) and WiMAX
(Worldwide Interoperability for Microwave Access) operate best in
licensed spectrum covering large outdoor environments. It is also
expected that multi-mode wireless devices shall become widespread.
Hence, it is of great interest to the mobile operators, technology
users, and vendors to provide seamless mobility between these
heterogeneous access technologies with uninterrupted service
continuity.
[0002] The current technologies have focused on pure layer 3 (L3)
mobility solutions such as Mobile IP (Internet Protocol). Although,
these technologies support an inter-access mobility solution, the
handoff delay could be extremely high. Furthermore, such L3
mobility procedures rely completely on the mobile device to make a
handoff decision. These solutions rely on dual radio operation,
i.e., both the radios involved in handover would be transmitting at
the same time. However, this may not always be possible, because
due to interference, platform noise and/or co-existence issues, it
might only be possible to have a single radio operating at any
point in time.
[0003] This disclosure proposes an alternative architecture to
support a Single Radio Handover solution leading to tighter
handover control and synchronization and overall lower latency of
handovers and packet loss.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 shows an example of architecture for optimized single
radio handover using L2 tunneling between WiMAX and 3GPP networks,
utilized in an embodiment of this invention.
[0005] FIG. 2 shows a high level flow of Control Plane and Data
Path setup Signaling between 3GPP and WiMAX networks, utilized by
an embodiment of this invention.
[0006] FIG. 3(a) and (b) show the detailed low latency handover
flow from E-UTRAN to WiMAX networks, based on L2 tunneling between
WiMAX and 3GPP, utilized by an embodiment of this invention.
[0007] FIG. 4 shows an example of architecture for optimized single
radio handover using L2 tunneling between WiMAX and legacy 2G/3G
networks (via 3GPP), utilized in an embodiment of this
invention.
[0008] FIG. 5 shows the low latency handover flow from WiMAX to
legacy 2G/3G networks based on L2 tunneling between WiMAX and 3GPP,
utilized by an embodiment of this invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] An embodiment of this invention uses an alternative
architecture to for single radio handover between two wireless
networks such as WiMAX and 2G/3G/4G. This embodiment uses a Data
Link Layer (L2) tunneling between the source/target and core (e.g.,
evolved packet core) networks to achieve a tighter handover control
and synchronization, support for network initiated handoffs based
on operator policy and Radio resource management (RRM), and overall
lower latency of handovers and packet loss. In one embodiment, the
actual path between the two entities is still IP based, but the
tunnel carries L2 messages, as opposed to L3 messages.
[0010] In an embodiment of this invention, (referring to FIG. 1), a
user equipment (UE) (110), which is connected to a source wireless
network such as an E-UTRAN (evolved-universal mobile
telecommunication system (UMTS) terrestrial radio access network)
(150) via an evolved-node B (eNB) (152), is handed over to a target
wireless network, such as WiMAX (120). At the completion of the
handover, UE will be able to communicate with an operator's IP
services (140) (such as IP Multimedia Subsystem (IMS) and Packet
Switch Service (PSS)) through a WiMAX Access Service Network (ASN)
(122) and a Packet Data Network (PDN) gateway (136) (such as one in
a 3.sup.rd Generation Partnership Project (3GPP) network (130)). In
this example, prior to handover, UE (110) communicates with the
operator's IP services (140) though eNB (152), a Serving Gateway
(S-GW) (134) in 3GPP (130) network, and the PDN Gateway (136).
[0011] To achieve this handover, in an embodiment, the WiMAX ASN
(122) and a Mobility Management Entity (MME) (132) in the 3GPP core
network (130) establish an L2 tunnel (124) to exchange control
signals, such as pre-registration, pre-authentication, context
transfer, and handover command, while UE (110) is still connected
to the E-UTRAN (150). In an embodiment of this invention, a bearer
path (126) is also set up between the WiMAX ASN (122) and the
Serving Gateway (134) to use for data packet forwarding between the
3GPP and WiMAX networks. In one embodiment, the forwarded packets
sent via this bearer path (126), e.g., from/to 3GPP network to/from
WiMAX network, reduces the amount of re-transmission of the data
packets, while UE (110) hands over the connection from the source
to target network.
[0012] In an embodiment of this invention, the handover latency
between the source and target networks is reduced by establishing
the required control signaling before the actual handover of the
data connection through the L2 tunnel connection.
[0013] A high level flow (FIG. 2) used in an embodiment of this
invention demonstrates the examples of one or more control
signaling, such as Pre-Registration, Pre-Authentication, Context
Transfer, and Handover Command, that are transmitted through L2
tunnel between a core network and a target network (or a source
network), such as 3GPP and WiMAX networks, through networks
elements, such as a 3GPP MME in 3GPP network and a WiMAX ASN
Authenticator in WiMAX network. In one embodiment, one or more of
such control signals are associated with the Control Plane.
[0014] An embodiment of this invention uses packet forwarding
between a core network and a target network, such as 3GPP and WiMAX
networks (e.g., see the packet forwarding flow illustrated in FIG.
2). In an embodiment, the data packets are forwarded between
network elements, such as a 3GPP Serving Gateway and WiMAX ASN Data
Packet Forwarding (DPF), after a handover event occurs (e.g., when
WiMAX ASN sends a Handover Command (response)). In one embodiment,
the packet forwarding occurs through a bearer path setup during the
control signaling.
[0015] FIG. 3(a) and (b) illustrate an example of a handover flow
used in an embodiment of this invention using a Long-Term Evolution
(LTE) access network, e.g., E-UTRAN, as the source network and
WiMAX as the target network through 3GPP System Architecture
Evolution (SAE) network. Prior to the handover, UE communicates to
an IP cloud (IP services) via PDN Gateway/Home Agent (GW/HA). The
user data flow between UE and PDN GW/HA through eNB (in E-UTRAN)
and Serving Gateway (in 3GPP).
[0016] In one embodiment, one or more WiMAX system information
elements are broadcast to UE from eNB or MME (FIG. 3(a)). In an
alternate embodiment, UE obtains target network information (e.g.,
for WiMAX neighboring cells) in one or more ways, such as cached
information, pulled or pushed information from services such as
network access provider, network service provider operator, an
operator's IP service, or any other service, from target network
directly, or directly or indirectly from a "peer" UE. In one
embodiment, the examples of one or more types of information
obtained about a target network such as WiMAX are shown in Table
1.
[0017] In one embodiment, UE measures the radio parameter in a
source network (e.g., E-UTRAN), and provides the source network
(e.g., eNB) such measurement.
[0018] In one embodiment, UE starts measuring target network radio
parameters, e.g., when the source network (e.g., E-UTRAN) parameter
values fall below threshold, or alternatively, when UE receives a
message from source network (e.g., eNB) to start radio measurement
in target network. For example, in one embodiment, UE uses short
occasional gaps in communications in E-UTRAN to temporarily turn
off 3GPP radio (e.g., .about.10 msec) and perform measurement in
WiMAX network with WiMAX ASN. In one embodiment, parameters such as
Received Signal Strength Indication (RSSI), Carrier to
Interference-plus-Noise Ratio (CINR), Cell Type, Quality of Service
(QoS) Parameters are examined and a selection criteria is
checked.
[0019] In one embodiment, the decision to handover to target
network (e.g., WiMAX) is network initiated, e.g., based on operator
policy, or Radio Resource Management (RRM). In an alternate
embodiment, the decision to handover is determined by UE. In one
embodiment, a source network element, e.g., eNB (in source network
such as E-UTRAN), sends a handover preparation message to UE. In an
alternate embodiment, such message is initiated by MME or other
network elements. In an alternate embodiment, handover preparation
is self-initiated by UE.
[0020] In one embodiment, an L2 tunnel is established between the
core and the target (or source) network elements, e.g., between MME
in 3GPP and WiMAX ASN, and UE communicates with one or more target
network elements through this L2 tunnel. In one embodiment, this L2
tunnel is reused by the source/target networks for multiple
handover events. In one embodiment, communication between UE and
the target network element such as WiMAX ASN, is supported via
tunneling in source network (e.g., via a E-UTRAN radio tunnel
between UE and eNB, and a tunnel between eNB and MME), in addition
to L2 tunnel between core network and target network (e.g., MME in
3GPP and WiMAX ASN).
[0021] In an embodiment, UE performs registration with target
network through L2 tunnel, e.g., in one embodiment, UE performs
WiMAX Registration with WiMAX ASN. In one embodiment, UE and the
target network element (e.g., WiMAX ASN) communicate messages
(e.g., Handover request/response) through L2 tunnel.
[0022] In one embodiment, UE and an authentication/authorization
service such as HSS/AAA (Home Subscriber Server/Authentication,
Authorization and Accounting AAA) perform a security action, such
as pre-authentication, through L2 tunnel.
[0023] In one embodiment, context information is passed to target
network, e.g., WiMAX ASN, to support handover. Examples of context
information include: information to establish types of connection
(e.g., voice, bursty), security attributes, MAC context, Proxy
Mobile IP (PMIP) context, and other context information
communicated via Feature Profile Types (FPTs).
[0024] In one embodiment, target network, e.g., WiMAX ASN, performs
resource allocation/reservation for UE to support the UE
handover.
[0025] In one embodiment, a target network element (e.g., WiMAX
ASN) and source network element (e.g., Serving Gateway in 3GPP)
setup a bearer path to forward packets to/from UE.
[0026] In one embodiment, target network, e.g., WiMAX ASN, sends
Handover Command (or a Handover response) to UE, through L2 tunnel.
In one embodiment, target network (e.g., WiMAX ASN) notifies core
network (e.g., MME) of Handover command through L2 tunnel.
Alternatively, UE notifies core network of Handover completion.
[0027] In one embodiment, a core network element (e.g., MME in
3GPP) sends a message to a core network gateway (e.g., Serving
Gateway in 3GPP) to start forwarding data packets to target network
through a bearer path. In one embodiment, after establishing the
bearer path, Serving Gateway determines when UE has moved to target
Radio Access Technology (RAT) based on HARQ/ARQ retransmissions
(e.g., within 50 msec), in order to commence forwarding packets to
target network through the bearer path.
[0028] In one embodiment, having received the handover command
(response), UE switches its radio to target network, and completes
network entry to target network.
[0029] Handover latency is the duration between UE receiving
Handover command and UE completing target network entry.
[0030] In one embodiment, UE receives forwarded user data sent to
target network via the bearer path.
[0031] In one embodiment, target network (e.g., WiMAX ASN) sends
PMI Binding Update message to PDN Gateway/HA to receive the data
for UE. At the completion of the handover, UE user data flows
through target network (e.g., WiMAX ASN) and PDN Gateway.
[0032] In one embodiment of this invention (referring to FIG. 4), a
user equipment (UE) (410), which is connected to a source wireless
network such as an WiMAX (420) via WiMAX ASN (422), is handed over
to a target wireless network, such as UTRAN (460) (or GERAN (470)).
At the completion of the handover, UE will be able to communicate
with an operator's IP services (440) through a 2G/3G network
access, e.g., Serving GPRS Support Node (SGSN) (466), Serving
Gateway (434), and a PDN gateway (436).
[0033] One embodiment uses a virtual eNB (438) in 3GPP network. In
one embodiment, the virtual eNB has a Radio Network Controller
(RNC) like functionality to allow UTRAN (460) (or GERAN (470)) to
take advantage of low latency L2 handoffs with little impact to
legacy 2G/3G networks, SGSN or MME.
[0034] In one embodiment, the control signaling to handover from
source network (e.g., WiMAX) to target network (e.g., UTRAN or
GERAN) is performed through an L2 tunnel (424) between source
network (e.g., WiMAX ASN (422)) and 3GPP MME (432). In one
embodiment, a bearer data path (426) is established for data packet
forwarding between source network, e.g., WiMAX, and Serving Gateway
(434) to pass the data packet during the handover.
[0035] In one embodiment, UE performs an attach procedure with MME
in 3GPP through L2 tunnel from source network (e.g., WiMAX),
without leaving source network. In one embodiment, the resources in
target network are setup through SGSN (466).
[0036] FIG. 5 illustrate an example of a handover flow (e.g.,
through SAE network) used in an embodiment of this invention using
WiMAX as the source network and UTRAN as the target network. Prior
to the handover, UE communicates to an IP cloud via PDN Gateway and
WiMAX ASN.
[0037] In one embodiment, the decision to handover from source
network (e.g., WiMAX) to target network (e.g., UTRAN (460) or GERAN
(470)) is network initiated (e.g., based on network RRM and
measurement of radio parameters in source and/or target
network).
[0038] In one embodiment, source network (e.g., WiMAX ASN) sends UE
a message to prepare for handover. In an alternate embodiment, UE
initiates the handover process.
[0039] In an embodiment, UE performs an attach procedure (e.g.,
UTRAN attach procedure) with MME, Serving Gateway, and PDN gateway
in 3GPP via an L2 tunnel established between source network (e.g.,
WiMAX ASN) and 3GPP MME and a tunnel within source network (e.g.,
WiMAX radio tunnel).
[0040] In one embodiment, MME sends resource setup request to the
target access network (e.g., SGSN) to allocate resource for UE
handover.
[0041] In one embodiment, MME sends an update message to Serving
Gateway to update the location of UE.
[0042] In one embodiment, MME sends a Handover command to a virtual
eNB which sends the Handover to UTRAN to UE via L2 tunnel to source
network.
[0043] In one embodiment, source network (e.g., WiMAX ASN) and core
network (e.g., Serving Gateway in 3GPP) elements establish a bearer
path to forward packets to/from UE during handover.
[0044] In one embodiment, UE switches its radio to target network
(e.g., UTRAN), and completes handover with target network access
(e.g., SGSN), e.g., via Radio Resource Control (RRC) response
message. In one embodiment, SGSN sends PMIP Proxy Binding Update to
PDN Gateway. At this point, user data flows from UE through target
network (e.g., in case of UTRAN (460), through NodeB (464) and RNC
(462); or in case of GERAN (470), through Base Station Subsystem
(BSS), including Base Transceiver System (BTS) (474) and Packet
Control Unit/Base Station Controller (PCU/BSC) (472)), 2G/3G
network access (e.g., SGSN), 3GPP Serving Gateway, and PDN
Gateway.
[0045] In one embodiment of this invention, UE is handed over from
WiMAX network to E-UTRAN, through similar steps as shown in FIG. 5,
and in similar architecture as shown in FIG. 4. However, the
E-UTRAN resource allocation message is sent from MME to an eNB in
E-UTRAN network, and UE upon receiving handover command, switches
radio to E-UTRAN with Serving Gateway performing PMIP Binding
Update with PDN Gateway for user data flow commence between UE and
PDN Gateway through eNB (in E-UTRAN) and 3GPP Serving Gateway.
TABLE-US-00001 TABLE 1 Examples of WiMAX System Information
obtained by a UE (e.g., via broadcast at source network(s) such as
E-URAN/UTRAN) Type Description Downlink Identifies the DL center
carrier frequency of (DL) center WiMAX neighboring cells. carrier
In one example, DL center carrier frequency frequency is a multiple
of 250 kHz. Cell Identifies the size of cell bandwidth. bandwidth
Preamble Identifies the PHY-specific preamble for the index WiMAX
neighboring based station (BS). BS ID Base Station ID is a global
unique identifier for a WiMAX base station, as defined in the IEEE
Std 802.16-2004 and IEEE Std 802.16e-2005 standard. The BS ID
represents a logical instance of a PHY and MAC function providing
802.16 radio connectivity services to an mobile station
(MS)/subscriber station (SS) (equivalent to a single frequency
sector of a physical base station). NAP ID NAP (Network Access
Provider) is a business entity that provides WiMAX radio access
infrastructure to one or more WiMAX Network Service Providers
(NSPs). A NAP implements this infrastructure using one or more
Access Service Networks (ASNs). NAP ID is contained in the upper 24
bits of BS ID. NSP ID NSP (Network Service Provider) is a business
entity that provides IP connectivity and WiMAX services to WiMAX
subscribers compliant with the Service Level Agreement it
establishes with WiMAX subscribers. To provide these services, an
NSP establishes contractual agreements with one or more NAPs.
Additionally, an NSP may also establish roaming agreements with
other NSPs and contractual agreements with third-party application
providers (e.g. ASP or ISPs) for providing WiMAX services to
subscribers. MAC MAC Version specifies the version of. Version IEEE
802.16 for BS/MS. System This indicates the Mobile WiMAX Version
release as specified by the WiMAX Forum Mobile Air Interface System
Profile. Available This indicates the average ratio of downlink
non-assigned DL radio resources to (DL) Radio the total usable DL
radio resources. The average Resources ratio shall be calculated
over a time interval defined by the DL_radio_resources_window_size
parameter. The reported average ratio will serve as a relative load
indicator. Available This indicates the average ratio of
non-assigned uplink (UL) UL radio resources to the total usable UL
radio Radio resources. The average ratio shall be Resources
calculated over a time interval defined by the
UL_radio_resources_window_size parameter. The reported average
ratio will serve as a relative load indicator. Cell Type This
specifies the cell size for hierarchical cell architecture. A lower
value of "Cell Type" can represent a smaller value for cell size
and a higher value of "Cell Type" can represent larger cell size.
Based on the frequency of handovers, decision can be made to move
to a larger cell (in case of high handover frequency) or to a
smaller cell (in case of low handover frequency). Optimized This
flag specifies if optimized handover is Handover supported by the
3GPP system. Support Address of This specifies the address
Interworking of the inter-working function entity that Function may
be used in optimized handovers. (IWF)
[0046] In one embodiment, target network (e.g., WiMAX) system
information is broadcast in source access network e.g., 2G/3G/4G
networks or Wi-Fi.TM. network, to facilitate network discovery and
selection.
[0047] One embodiment of this invention achieves low latency
handoffs between access networks with no need for simultaneous
radio operation to reduce or eliminate issues related to
co-existence and/or platform interference.
[0048] In one embodiment, a low latency L2 tunnel is established
between core network and target (or source) access network, e.g.,
between 3GPP MME and WiMAX ASN, for control plane signaling.
[0049] One embodiment of this invention reduces inter-RAT handoff
delays as the context and security parameters are transferred
through networks in the preparation phase. In one embodiment,
pre-registration, pre-authentication and context transfer to the
target network is performed while UE is connected to source access
network and maintains connections over the source access
network.
[0050] In one embodiment, a bearer path is setup between core
network and target (or source) network, e.g., between 3GPP Serving
Gateway and WiMAX ASN data packet forwarding function. In one
embodiment, once the handover command is sent, packet forwarding
happens with lower latency leading to a much smoother handoff than
with an L3 tunnel. In this embodiment, through L2 tunneling, the
source is informed of final tunneled message (e.g., Handover
Command) that the UE is moving to target RAT and/or the core
network determines UE leaving the source network based on HARQ/ARQ
retransmissions, e.g., within about 50 msec. Thus, in one
embodiment, packet forwarding to target network commences within
about 50 msec, whereas for L3 tunnel this could take about 1 second
to detect.
[0051] In an embodiment of this invention, a virtual eNB
(equivalent to RNC like functionality) allows UTRAN/GERAN networks
to take advantage of low latency L2 handoffs with minimum impact to
legacy 2G/3G networks (with minimal impact to SGSN and MME).
[0052] An embodiment of this invention uses low latency handovers
between Mobile WiMAX and 2G/3G/LTE with a single radio transmitting
at UE at any given point of time. One embodiment of this invention
uses access independent network interfaces with L2 tunneling and
single radio handover.
[0053] In an embodiment of this invention, UE is implemented in a
(embedded or not-embedded) mobile device, e.g., a communication
processor. In an embodiment of this invention, UE is implemented in
products such as multi-mode radio product, laptop, mobile
intelligent device, personal digital assistant, or mobile
phone.
[0054] The embodiments above are provided to illustrate the
invention. Other radio access networks, as source or target, are
considered part of this invention. Examples of such radio networks
include WiMAX, 2G/3G/LTE, GERAN, UTRAN, E-UTRAN, and Wi-Fi.
[0055] Any variations of the above teachings are also intended to
be covered by this patent application.
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