Title of Invention

METHOD FOR IMPROVED LINK LAYER HANDOFF, ACCESS NETWORK AND MOBILE NODE WITH IMPROVED LINK LAYER HANDOFF

Abstract Various embodiments are described to address the need for an apparatus and method that improves link layer handoff by addressing the packet-loss problem existing today. An intermediate buffer management layer (IBML) (201, 211) is introduced below layer 3 of an OSI-based communications interface. The IBML buffers copies of OSI layer 3 packets being transmitted via lower layers (205, 215) of the interface and manages the buffer contents using indications the IBML receives from one or more of the lower layers. When the IBML receives an indication that a link layer hard handoff is imminent, , the IBML transfers the presently buffered packets to a corresponding IBML (202, 212) in the target communications interface. This sub-layer 3 buffer transfer enables the target communications interface to reduce packet-loss associated with the hard handoff.
Full Text Field of the Invention
The present invention relates generally to communication systems
and, in particular, to improved link layer handoff in wireless communication
systems.
Background of the Invention
Packet switched wireless access networks contain AN (Access
Network) elements that are connected to AR (Access Router) elements.
Typically, an AR serves an MN (Mobile Node) via the AN which is presently
serving the MN. Again typically, an AR performs the function of a mobility
agent to support the network layer mobility of the MN. In the event of an inter-
AR handoff of the MN within the same wireless technology or across different
wireless technologies, the mobility agent for the MN switches from the source
AR to the target AR. This results in a new link layer connection being
established between the MN and the new AR.
The re-establishment of a new link layer connection with the target AN
causes the link layers (e.g., the ARQ layer) of both the source AN and the MN
to flush their outstanding transmit and re-transmit queues. The flushing of
outstanding radio frames can result in a noticeable performance impact for
the affected end-to-end applications, especially VoIP-based (voice over
internet protocol) and PTT-based (push-to-talk) applications. Such packet
loss may also cause a TCP (Transmission Control Protocol) sender to initiate
congestion control by invoking the slow start procedure. This may, in turn,
impact the end-to-end performance of the TCP-based application.
Therefore, a need exists for an apparatus and method that improves
link layer handoff by addressing the packet-loss problem existing today.

Brief Description of the Accompanying Drawings
FIG. 1 is a block diagram depiction of a wireless communication
system in accordance with multiple embodiments of the present invention.
FIG. 2 is a block diagram depiction of Open Systems Interconnection
(OSI)-based communication interfaces active in an MN (mobile node), a
source AN (access network), and a target AN during a link layer handoff from
the source AN to the target AN by the MN, in accordance with multiple
embodiments of the present invention.
FIG. 3 is a block diagram depiction of a protocol stack for an IEEE
(lnstitute of Electrical and Electronics Engineers) 802.XX-based access
network, in accordance with multiple embodiments of the present invention.
FIG. 4 is a block diagram depiction of a protocol stack for a 3GPP2
(3rd Generation Partnership Project 2)-based access network, in accordance
with multiple embodiments of the present invention.
FIG. 5 is a logic flow diagram of functionality performed by an IBML
(intermediate buffer management layer) in accordance with multiple
embodiments of the present invention.
Specific embodiments of the present invention are disclosed below
with reference to FIGs. 1-5. Both the description and the illustrations have
been drafted with the intent to enhance understanding. For example, the
dimensions of some of the figure elements may be exaggerated relative to
other elements, and well-known elements that are beneficial or even
necessary to a commercially successful implementation may not be depicted
so that a less obstructed and a more clear presentation of embodiments may
be achieved. Simplicity and clarity in both illustration and description are

sought to effectively enable a person of skill in the art to make, use, and best
practice the present invention in view of what is already known in the art. One
of skill in the art will appreciate that various modifications and changes may
be made to the specific embodiments described below without departing from
the spirit and scope of the present invention. Thus, the specification and
drawings are to be regarded as illustrative and exemplary rather than
restrictive or all-encompassing, and all such modifications to the specific
embodiments described below are intended to be included within the scope of
the present invention.
Detailed Description of Embodiments
Various embodiments are described to address the need for an
apparatus and method that improves link layer handoff by addressing the
packet-loss problem existing today. An intermediate buffer management layer
(IBML) is introduced below layer 3 of an OSI-based communications
interface. The IBML buffers copies of OSI layer 3 packets being transmitted
via lower layers of the interface and manages the buffer contents using
indications the IBML receives from one or more of the lower layers. When the
IBML receives an indication that a link layer hard handoff is proceeding, the
IBML transfers the presently buffered packets to a corresponding IBML in the
target communications interface. This sub-layer 3 buffer transfer enables the
target communications interface to reduce packet-loss associated with the
hard handoff.
The disclosed embodiments can be more fully understood with
reference to FIGs. 1-5. FIG. 1 is a block diagram depiction of a wireless
communication system 100 in accordance with multiple embodiments of the
present invention. At present, standards bodies such as OMA (Open Mobile
Alliance), 3GPP (3rd Generation Partnership Project), 3GPP2 (3rd
Generation Partnership Project 2) and IEEE (Institute of Electrical and
Electronics Engineers) 802 are developing standards specifications for
wireless telecommunications systems. (These groups may be contacted via

http://www.openmobilealliance.com. http://www.3app.ora/.
http://www.3gpp2.com/ and http://www.ieee802.org/. respectively.)
Communication system 100 represents a system having access networks
based on different wireless technologies. For example, the description that
follows will assume that AN 121 is IEEE 802.XX-based while AN 122 is
3GPP2-based. Thus, AN 121 employs wireless technologies such as IEEE's
802.11, 802.16, or 802.20, while AN 122 employs wireless technologies such
as CDMA 2000 or HRPD (also known as 1xEV-DO or IS-856), both ANs 121
and 122 suitably modified to implement the present invention. Alternative
embodiments of the present invention may be implemented in communication
systems that employ other or additional technologies such as, but not limited
to, those described in the 3GPP specifications (e.g., GSM, GPRS, EDGE, W-
CDMA, UTRAN, FOMA, UMTS, HSDPA, and HSUPA), those described in the
lS-136 (TDMA Third Generation Wireless Standards) specification, those
described in the IS-95 (CDMA) specification, 1xEV-DV technologies, and
integrated dispatch enhanced network technologies.
More specifically, communication system 100 comprises mobile node
(MN) 101, access networks (ANs) 121 and 122, access routers (ARs) 141
and 142, and packet network 151. Those skilled in the art will recognize that
FIG. 1 does not depict all of the network equipment necessary for system 100
to operate but only those system components and logical entities particularly
relevant to the description of embodiments herein. For example, ANs are
known to comprise devices such as WLAN (wireless local area network)
stations (which include access points (APs), AP controllers / switches, and/or
WLAN switches), base transceiver stations (BTSs), base site controllers
(BSCs) (which include selection and distribution units (SDUs)), packet control
functions (PCFs), packet control units (PCUs), and/or radio network
controllers (RNCs). However, none of these devices are specifically shown in
FIG. 1.
Instead, ANs 121 and 122 are depicted in FIG. 1 as comprising
processing units 125 and 126, network interfaces 127 and 128, and
transceivers 123 and 124. In general, components such as processing units,
network interfaces, and transceivers are well-known. For example, AN

processing units are known to comprise basic components such as, but not
limited to, microprocessors, microcontrollers, memory devices, application-
specific integrated circuits (ASICs), and/or logic circuitry. Such components
are typically adapted to implement algorithms and/or protocols that have been
expressed using high-level design languages or descriptions, expressed
using computer instructions, expressed using messaging flow diagrams,
and/or expressed using logic flow diagrams.
Thus, given an algorithm, a logic flow, a messaging flow, and/or a
protocol specification, those skilled in the art are aware of the many design
and development techniques available to implement an AN processing unit
that performs the given logic. Therefore, ANs 121 and 122 represent known
ANs that have been adapted, in accordance with the description herein, to
implement multiple embodiments of the present invention. Furthermore, those
skilled in the art will recognize that aspects of the present invention may be
implemented in and across various physical components and none are
necessarily limited to single platform implementations. For example, the AN
aspect of the present invention may be implemented in any of the AN devices
listed above or distributed across such components.
ANs 121 and 122 use wireless interfaces 111 and 112 for
communication with MN 101. Since, for the purpose of illustration, AN 121 is
IEEE 802.XX-based while AN 122 is 3GPP2-based, wireless interfaces 111
and 112 correspond to an IEEE 802.XX air interface and a 3GPP2 air
interface, respectively.
MN platforms are known to refer to a wide variety of consumer
electronic platforms such as, but not limited to, mobile stations (MSs), access
terminals (ATs), terminal equipment, gaming devices, personal computers,
and personal digital assistants (PDAs). In particular, MN 101 comprises
processing unit 102, transceiver 103, a keypad (not shown), a speaker (not
shown), a microphone (not shown), and a display (not shown). Processing
units, transceivers, keypads, speakers, microphones, and displays as used in
MNs are all well-known in the art.
For example, MN processing units are known to comprise basic
components such as, but not limited to, microprocessors, digital signal

processors (DSPs), microcontrollers, memory devices, application-specific
integrated circuits (ASICs), and/or logic circuitry. Such MS components are
typically adapted to implement algorithms and/or protocols that have been
expressed using high-level design languages or descriptions, expressed
fusing computer instructions, expressed using messaging flow diagrams,
and/or expressed using logic flow diagrams. Thus, given an algorithm, a logic
flow, a messaging/signaling flow, a call flow, and/or a protocol specification,
those skilled in the art are aware of the many design and development
techniques available to implement user equipment that performs the given
logic. Therefore, MN 101 represents a known MN that has been adapted, in
accordance with the description herein, to implement embodiments of the
present invention.
Operation of various embodiments in accordance with the present
invention occur substantially as follows. Relevant operation begins with AN
121, MN 101, or both AN 121 and MN 101 sending messaging to each other
via wireless interface 111 using an Open Systems Interconnection (OSI)-
based communications interface. In particular, the OSI-based communication
interfaces are employed by processing units 125 and 102 to transmit
messaging via respective transceivers 123 and 103 to MN 101 and AN 121,
respectively. While sending and receiving messaging, a hard handoff from
serving, or source, AN 121 to target AN 122 occurs.
FIG. 2 is a block diagram depiction of OSI-based communication
interfaces active in MN 101, source AN 121, and target AN 122 during a link
layer handoff by MN 101 from source AN 121 to target AN 122, in accordance
with multiple embodiments of the present invention. OSI-based
communication interfaces are depicted as being implemented by source AN
processing unit 125, target AN processing unit 126, and MN processing unit
102. MN processing unit 102 is depicted as implementing an OSI-based
communication interface for each AN, AN 121 and AN 122 utilizing different
wireless signaling technologies. Each communications interface comprises
processing layers based on the OSI layering model. In FIG. 2, layer 3 is
depicted by blocks 203, 204, 213 and 214 in each communications interface,
while lower layers (layers below layer 3) are depicted by blocks 205, 206, 215

and 216. Embodiments of the present invention, also include an additional
layer, an intermediate buffer management layer (IBML), depicted by blocks
201,202,211 and 212.
FIGs. 3 and 4 depict examples of portions of OSI-based
communication interfaces implemented by some embodiments of MN 101,
source AN 121, and target AN 122. FIG. 3 is a block diagram depiction of
protocol stack 300 for an IEEE 802.XX-based access network. Thus, as an
example, protocol stack 300 depicts protocol stack layers that layers 201, 203
and 205 as well as layers 211, 213 and 215 implement. In the case of
protocol stack 300, lower layers 205 and 215 each comprise a Logical Link
Control (LLC) layer, a MAC Layer Management Entity (MLME), a Physical
Layer Management Entity (PLME), a Medium Access (MAC) layer, and a
physical layer.
Similarly, FIG. 4 is a block diagram depiction of protocol stack 400 for
a 3GPP2-based access network. Thus, as an example, protocol stack 400
depicts protocol stack layers that layers 202, 204 and 206 (see SDU stack) as
well as layers 212, 214 and 216 implement (see MS stack). In the case of
protocol stack 400, lower layers 206 and 216 each comprise a Radio Link
Protocol (RLP) layer among others.
Both protocol stacks 300 and 400 include an intermediate buffer
management layer between layer 3 and the link layer ARQ functionality below
layer 3. Source AN processor 125 buffers copies of OSI layer 3 packets in
IBML 201. These are OSI layer 3 packets being transmitted via lower layers
205 to MN 101. Likewise, MN processor 102 buffers copies of OSI layer 3
packets in IBML 211. These are OSI layer 3 packets being transmitted via
lower layers 215 to AN 121.
Lower layers 205 and 215 then operate to determine whether all
portions of the transmitted packets were successfully transmitted. For
example, an automatic retransmission request (ARQ) layer of lower layers
205 and 215 may use implicit / explicit ACK/NAK along with a mapping table
that maps higher layer packet IDs (e.g., IP id) to the sequence number of
segments belonging to the corresponding ARQ frames to determine whether
all the segments belonging to a layer 3 packet have been received or not.

When lower layers 205 or 215 determine that a packet has been
successfully transmitted, an indication is sent to the respective IBML 201 or
211. Generally, these indications may take the form of triggers, events, or
messages of some form. For example, in some embodiments, these
indications that a buffered packet has been successfully transmitted comprise
LLC primitives. As depicted by FIG. 3, LLC_SAP (LLC service access point),
used by IBMLs 201 and 211 to send and receive data, can also be used to
convey an LLC primitive (e.g., TX-SUCCESS-IND) indicating a successful
packet transmission. When IBML 201 or 211 receives a successful transmit
indication, the successfully transmitted packet is removed from the IBML
buffer.
In the above example, lower layers 205 and 215 use link layer specific
means to detect whether packets have been transmitted successfully over the
wireless link or not. If lower layers 205 and 215 are unable to detect that
packets have been successfully received by their respective peer entities,
IBMLs 201 and 211 can use a timer based approach to decide when to flush
the content of their respective buffers. In particular, IBMLs 201 and 211 may
use a blackout timer to decide how long to buffer layer 3 packets in the
absence of an indication of successful (or failed) transmission. When IBMLs
201 and 211 detect a timer expiration of a timer associated with a buffered
packet, IBMLs 201 and 211 remove the buffered packet from their respective
buffers. The timeout value of these blackout timers can be set equal to the
particular link layer handoff blackout time.
Lower layers 205 and 215 also operate to determine whether a
transmitted packet was not successfully transmitted. For example, an ARQ
layer of lower layers 205 and 215 detects when one or more segments of a
buffered packet has been aborted. This may be the result of a MAC (Medium
Access) layer abort or, in the case of a 3GPP2-based communications
interface, an H-ARQ (hybrid automatic retransmission request) abort, an RLC
(Radio Link Control) abort, or an RLP (Radio Link Protocol) abort.
When lower layers 205 or 215 determine that a packet has failed a
transmission attempt, an indication is sent to the respective IBML 201 or 211.
Again, these indications may generally take the form of triggers, events, or

messages of some form. For example, in some embodiments, these
indications that buffered packets have failed in transmission comprise MAC
Layer Management Entity (MLME) primitives. As depicted by FIG. 3,
MLME_SAP (MLME service access point) can be used to convey an MLME
primitive (e.g., TX-FAIL-IND) indicating a failed packet transmission. When
IBMLs 201 and 211 receive such indications, IBMLs 201 and 211 attempt to
retransmit the failed packet via respective lower layers 205 and 215.
Lower layers 205 and 215 also operate to determine that a link layer
hard handoff from source AN 121 to target AN 122 is proceeding (i.e.,
imminent or in-process). When lower layers 205 or 215 determine that such a
handoff is proceeding, an indication is sent to the respective IBML 201 or
211. Again, these indications may generally take the form of triggers, events,
or messages of some form that originate from the operating handoff
controller. For example, in some embodiments, these indications that a
handoff is proceeding comprise MLME or PLME (Physical Layer Management
Entity) primitives. As depicted by FIG. 3, MLME_SAP or PLME_SAP (PLME
service access point) can be used to convey the appropriate MLME / PLME
primitive (e.g., L2-HO-INIT-IND) indicating a link layer hard handoff is
proceeding.
When IBML 201 receives a handoff proceeding indication, IBML 201
transfers the packets presently buffered at IBML 201 to target IBML 202 in
target AN 122. The transfer may be enabled by including in the handoff
indication address information associated with target IBML 202, such as the
network address of IBML 202 itself or an address of the WLAN station / AP /
BSC / SDU where IBML 202 can be found. With this information a tunnel may
be established to support the transfer between the ANs.
Somewhat differently, when IBML 211 receives a handoff proceeding
indication, IBML 211 transfers the packets presently buffered at IBML 211 to
target IBML 212 in the target OSI-based communications interface of MN
101. In this case, the transfer from IBML 211 to IBML 212 occurs internally
within MN 101 from the source communications interface to the target
communications interface. This transfer may be enabled by including in the

handoff indication an identifier of the target OSI-based communications
interface.
Target IBMLs 202 and 212 receive the packets previously buffered at
the respective source IBML 201 and 211. Upon the handoff completing,
SIBMLs 202 and 212 can retransmit these buffered packets via respective
lower layers 206 and 216. Thus, the buffering and subsequent transfer of
these buffered packets, when a link layer hard handoff is detected, can
reduce the number packets lost during such handoffs on both the uplink and
downlink.
As described above, lower layers 205 and 215 operate to determine
whether a transmitted packet was not successfully transmitted. When lower
layers 205 or 215 determine that a packet has failed a transmission attempt,
an indication is sent to the respective IBML 201 or 211, which then attempts
to retransmit the failed packet via respective lower layers 205 or 215. In some
15embodiments, the respective IBML 201 or 211 may also notify a transport
layer, such as TCP, that the radio link is poor. For example, if the frequency
of SDU-TX-FAIL-IND reaches a threshold, the respective IBML 201 or 211
may notify a local TCP to stop sending additional packets to its peer. The
local TCP then sends a TCP ACK to its peer, setting its window field to zero
and thereby requesting its peer to stop sending data. The invocation of
temporary end-to-end flow control (TCP persistence mode) works to prevent
additional packets being dropped over the radio link during handoff. This also
prevents TCP congestion control and slow start from being triggered due to
the loss of packets during handoff.
When the handoff is complete, the respective target IBML 202 or 212
receives an indication that the handoff has completed and can then notify
TCP that data transfer may resume. TCP, in turn, can resume data transfer
by sending a TCP ACK with a non-zero window size to its peer. In this
example, triggering TCP persistence mode enhances the performance of
TCP based applications by avoiding the TCP congestion control / slow start
procedure after handoff.
FIG. 5 is a logic flow diagram of functionality performed by an IBML in
accordance with multiple embodiments of the present invention. Logic flow

500 begins (501) with the IBML buffering (503) copies of layer 3 packets that
are being transmitted via one or more lower layers (i.e., below layer 3) of the
OSI-based communications interface. As the IBML continues to buffer copies
of new layer 3 packets, it acts on various received indications. When (505)
the IBML receives an indication that one of the buffered packets was
successfully transmitted or that a buffered packet's timer expired, the IBML
removes (507) the packet from its buffer. When (509) the IBML receives an
indication that the transmission attempt of one of the buffered packets failed,
the IBML retransmits (511) the failed packet via one or more of the lower
layers. Finally, when (513) the IBML receives an indication that a link layer
hard handoff is proceeding, the IBML transfers (515) its presently buffered
packets to a target IBML in a target OSI-based communications interface and
logic flow 500 ends (517).
Various embodiments of the present invention may also be expressed
in terms of changes to existing communications standards, such as IEEE
802.XX and 3GPP2. Although there are many ways that these and other
standards may be modified to embody the present invention, a couple of
specific examples are provided below.
The IEEE 802.XX protocol stack may be modified to include the IBML
and various indications. The modifications could include: integrating the IBML
between L3 and the LLC layer; adding an SDU-TX-SUCCESS-IND LLC
primitive to indicate to the IBML the successful transmission of an IP packet
over the radio link; adding an L2-HO-INIT-IND MLME or PLME primitive to
indicate to the IBML that the link layer handoff is imminent (as part of this
trigger, MLME or PLME will also provide an address of the target AP where
the mobile is being handed over to); having LLC send SDU-TX-SUCCES-IND
trigger through LLC_SAP; having PLME or MLME send L2-HO-INIT-IND
trigger through PLME or MLME SAP, respectively; having IBML use
LLC_SAP to send / receive data as well as receive link layer triggers.
With these changes, the IBML would buffer a higher layer packet
before sending it to the underlying LLC layer until LLC notifies the IBML,
using an SDU-TX-SUCCESS-IND primitive, that the packet has been
transmitted successfully over the radio link to the peer LLC entity. MLME or

PLME layer sends trigger information to the IBML once it detects that link
layer handoff is imminent or completed. The infrastructure IBML using
extended IAPP, or some other tunneling mechanism, transmits the buffered
IBML packets from the source AP to the target AP. The mobile uses this
trigger to transfer the buffered packets from the source interface to the target
interface.
The 3GPP2 protocol stack may be modified to include the IBML and
various indications. The modifications could include some or all of the
following: integrating the IBML between GRE and RLP sublayers of SDU in
infrastructure; integrating the IBML between PPP and RLP layers in the
mobile node; modifying RLP implementation such that it indicates to the IBML
(using SDU-TX-SUCCESS-IND primitive) when it detects that all the
segments of a PPP frame have been successfully transmitted to its peer
entity (the RLP transmitter may use the L_V(N) peer sequence number
update along with information such as mapping of IP Id to the sequence
numbers of RLP frames generated for the given IP packet to decide if IP
packet have been successfully received by its peer entity or not (the L_V(N)
peer information is received during RLP fill frame exchange)); modifying H-
ARQ to indicate to the IBML (using SDU-TX-SUCCESS-IND) primitive once
ACK associated with all the segments of an IP packet is received by the H-
ARQ layer of MAC-sub layer (the H-ARQ implementation should maintain
additional information such as a table containing the mapping of IP identifier
with H-ARQ PDU).
Benefits, other advantages, and solutions to problems have been
described above with regard to specific embodiments of the present
invention. However, the benefits, advantages, solutions to problems, and any
element(s) that may cause or result in such benefits, advantages, or
solutions, or cause such benefits, advantages, or solutions to become more
pronounced are not to be construed as a critical, required, or essential feature
or element of any or all the claims. As used herein and in the appended
claims, the term "comprises," "comprising," or any other variation thereof is
intended to refer to a non-exclusive inclusion, such that a process, method,
article of manufacture, or apparatus that comprises a list of elements does

not include only those elements in the list, but may include other elements not
expressly listed or inherent to such process, method, article of manufacture,
or apparatus.
The terms a or an, as used herein, are defined as one or more than
pone. The term plurality, as used herein, is defined as two or more than two.
The term another, as used herein, is defined as at least a second or more.
The terms including and/or having, as used herein, are defined as comprising
(i.e., open language). The term coupled, as used herein, is defined as
connected, although not necessarily directly, and not necessarily
mechanically. The terms program, computer program, and computer
instructions, as used herein, are defined as a sequence of instructions
designed for execution on a computer system. This sequence of instructions
may include, but is not limited to, a subroutine, a function, a procedure, an
object method, an object implementation, an executable application, an
applet, a servlet, a shared library/dynamic load library, a source code, an
object code and/or an assembly code.

We Claim:
1. A method for improved link layer handoff comprising:
buffering copies of packets by an intermediate buffer management layer
(IBML) (201, 211) in a source Open Systems Interconnection (OSI)-based
communications interface to produce a group of buffered packets, wherein the
packets are OSI layer 3 packets being transmitted via at least one lower layer of the
source OSI-based communications interface, lower layers being below OSI layer 3;
receiving, by the IBML from a lower layer of the at least one lower layer (205,
215), an indication that a link layer hard handoff is imminent;
transferring, by the IBML in response to the link layer hard handoff indication,
the group of buffered packets to a target IBML (202, 212) in a target OSI-based
communications interface.
2. The method as claimed in claim 1, wherein the at least one lower layer of the
source OSI-based communications interface comprises at least one protocol layer
from the group consisting of a Medium Access (MAC) layer, a Logical Link Control
(LLC) layer, a MAC Layer Management Entity (MLME), a Physical Layer
Management Entity (PLME), a Radio Link Protocol (RLP) layer, a Radio Link Control
(RLC) layer, an automatic retransmission request (ARQ) layer, and a hybrid
automatic retransmission request (H-ARQ) layer.
3. The method as claimed in claim 1, which involves:
receiving, by the IBML from a lower layer of the at least one lower layer, an
indication that a packet in the group of buffered packets has been successfully
transmitted;
removing, by the IBML in response to the successful transmission indication,
the successfully transmitted packet from the group of buffered packets prior to
transferring the group of buffered packets.
4. The method as claimed in claim 3, which involves:
determining, by a lower layer of the at least one lower layer, that all portions of
the successfully transmitted packet were successfully transmitted.
5. The method as claimed in claim 1, which involves:

detecting, by the IBML, a timer expiration for a packet in the group of buffered
packets;
removing, by the IBML in response to the timer expiration, the packet from the
group of buffered packets prior to transferring the group of buffered packets.
6. The method as claimed in claim 1, which involves:
receiving, by the IBML from a lower layer of the at least one lower layer, an
indication that a packet in the group of buffered packets has failed a transmission
attempt;
retransmitting, by the IBML in response to the failed transmission indication,
the failed packet via at least one lower layer of the source OSI-based
communications interface.
7. The method as claimed in claim 1, which involves:
receiving, by the IBML from a lower layer of the at least one lower layer, an
indication that a packet in the group of buffered packets has failed a transmission
attempt;
notifying a transport layer, by the IBML in response to the failed transmission
indication, that a radio link is poor.
8. The method as claimed in claim 7, which involves
receiving, by the target IBML, an indication that the link layer hard handoff has
completed;
notifying a transport layer, by the target IBML in response to the hard handoff
complete indication, that data transfer may resume.
9. An access network (AN) with improved link layer handoff, comprising:
a transceiver;
a network interface; and characterized by
a processing unit, communicatively coupled to the transceiver and the
network interface,
adapted to send and receive messaging via the transceiver using a
source Open Systems Interconnection (OSI)-based
communications interface that has an intermediate buffer
management layer (IBML) (201),

adapted to buffer copies of packets in the IBML to produce buffered
packets, wherein the packets are OSI layer 3 packets being
transmitted via at least one lower layer (205) of the source OSI-
based communications interface, lower layers being below OSI
layer 3,
adapted to determine that a link layer hard handoff to a target AN is
imminent,
adapted to transfer via the network interface, in response to the
handoff determination, the buffered packets to a target IBML
(202) in a target OSI-based communications interface of the
target AN.
10. A mobile node (MN) with improved link layer handoff, comprising:
a transceiver; and characterized by
a processing unit, communicatively coupled to the transceiver,
adapted to send and receive messaging via the transceiver using a
source Open Systems Interconnection (OSI)-based
communications interface that includes an intermediate buffer
management layer (IBML) (211),
adapted to buffer copies of packets in the IBML to produce buffered
packets, wherein the packets are OSI layer 3 packets being
transmitted via at least one lower layer (215) of the source OSI-
based communications interface, lower layers being below OSI
layer 3,
adapted to determine that a link layer hard handoff to a target AN is
imminent,
adapted to transfer, in response to the handoff determination, the
buffered packets to a target IBML (212) in a target OSI-based
communications interface of the MN.

Documents:

00138-kol-2006-abstract.pdf

00138-kol-2006-claims.pdf

00138-kol-2006-description complete.pdf

00138-kol-2006-drawings.pdf

00138-kol-2006-form 1.pdf

00138-kol-2006-form 2.pdf

00138-kol-2006-form 3.pdf

00138-kol-2006-form 5.pdf

138-KOL-2006-ABSTRACT 1.1.pdf

138-kol-2006-assignment.pdf

138-kol-2006-assignment1.1.pdf

138-KOL-2006-CANCELLED PAGES.pdf

138-KOL-2006-CLAIMS 1.1.pdf

138-kol-2006-correspondence-1.3.pdf

138-kol-2006-correspondence.pdf

138-kol-2006-correspondence1.1.pdf

138-KOL-2006-DESCRIPTION (COMPLETE) 1.1.pdf

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Patent Number 245914
Indian Patent Application Number 138/KOL/2006
PG Journal Number 06/2011
Publication Date 11-Feb-2011
Grant Date 04-Feb-2011
Date of Filing 16-Feb-2006
Name of Patentee MOTOROLA, INC.
Applicant Address 1303 EAST ALGONQUIN ROAD, SCHAUMBURG, ILLINOIS 60196, UNITED STATES OF AMERICA
Inventors:
# Inventor's Name Inventor's Address
1 SINGH, AJOY, K. 275 W. WATERBURY DRIVE, ROUND LAKE, ILLINOIS 60073, UNITED STATES OF AMERICA
2 BHATT YOGESH, B. 1106 N. PLUM GROVE ROAD, SCHAUMBURG, ILLINOIS 60173, UNITED STATES OF AMERICA
PCT International Classification Number H04Q 36/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11/289,044 2005-11-29 U.S.A.
2 60/659,132 2005-03-07 U.S.A.