U.S. patent application number 12/693099 was filed with the patent office on 2011-07-28 for application-layer handoff of an access terminal from a first system of an access network to a second system of the access network during a communication session within a wireless communications system.
This patent application is currently assigned to QUALCOMM Incorporated. Invention is credited to Arvind Santhanam, Bongyong Song.
Application Number | 20110182272 12/693099 |
Document ID | / |
Family ID | 43858473 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110182272 |
Kind Code |
A1 |
Santhanam; Arvind ; et
al. |
July 28, 2011 |
APPLICATION-LAYER HANDOFF OF AN ACCESS TERMINAL FROM A FIRST SYSTEM
OF AN ACCESS NETWORK TO A SECOND SYSTEM OF THE ACCESS NETWORK
DURING A COMMUNICATION SESSION WITHIN A WIRELESS COMMUNICATIONS
SYSTEM
Abstract
Embodiments are directed to an application-layer handoff of an
access terminal from a first system of an access network to a
second system of the access network during a communication session
within a wireless communications system. In an embodiment, the
access terminal sets up a communication session on the first
system. A multimedia client measures application-layer performance
parameters for the communication session supported by the first
system, and determines whether to handoff the communication session
to a second system based at least in part on the application-layer
performance parameters. If the multimedia client determines to
handoff the communication session to the second system, the
multimedia client initiates the handoff and the communication
session is transitioned to the second system.
Inventors: |
Santhanam; Arvind; (San
Diego, CA) ; Song; Bongyong; (San Diego, CA) |
Assignee: |
QUALCOMM Incorporated
San Diego
CA
|
Family ID: |
43858473 |
Appl. No.: |
12/693099 |
Filed: |
January 25, 2010 |
Current U.S.
Class: |
370/332 |
Current CPC
Class: |
H04W 36/0007 20180801;
H04W 36/30 20130101; H04W 36/14 20130101; H04W 80/12 20130101 |
Class at
Publication: |
370/332 |
International
Class: |
H04W 36/16 20090101
H04W036/16 |
Claims
1. A method of participating in a communication session within a
communications system, comprising: participating in a communication
session supported over a first system associated with a first
physical layer; monitoring one or more application-layer
performance parameters associated with the communication session;
determining, based at least in part on the monitoring step, whether
to hand off the communication session from the first system to a
second system associated with a second physical layer; and
selectively handing off the communication session from the first
system to the second system based on the determining step.
2. The method of claim 1, wherein the first system and/or the
second system corresponds to one or more of a WiFi system, a
CDMA2000 1x system, a Wideband CDMA (WCDMA) system, a frequency
division multiple access (FDMA) system, a time division multiple
access (TDMA) system, a orthogonal frequency division multiplexing
(OFDM) system, a long-term evolution (LTE) system, a broadcast and
multicast service (BCMCS) system and/or a multimedia
broadcast/multicast services (MBMS) system.
3. The method of claim 1, wherein the one or more application-layer
performance parameters include whether a location of an access
terminal (AT) satisfies a given relationship with respect to a
defined location region, a media error rate (MER) of the
communication session supported over the first system, an outage
duration (OD) of the communication session supported over the first
system and/or a charging rate associated with the communication
session supported over the first system.
4. The method of claim 1, wherein the determining step determines
to hand off the communication session from the first system to the
second system based in part on the monitoring step and also based
in part on an availability and/or application-layer performance
expectation of the second system in the event of a handoff.
5. The method of claim 1, wherein the first and/or second systems
supporting the communication session correspond to different
connection mechanisms of an access network through which an access
terminal (AT) participating in the communication session
communicates with an application server that is arbitrating the
communication session between the AT and at least one other AT.
6. The method of claim 1, wherein the one or more application-layer
performance parameters includes whether a location of an access
terminal (AT) satisfies a given relationship with respect to a
defined location region.
7. The method of claim 6, wherein the monitoring step includes:
determining the location of the AT; comparing the determined
location of the AT with the defined location region, the defined
location region defining an area where the first system can support
the communication session; and attempting a handoff of the
communication session from the first system to the second system if
the comparison indicates that the determined location of the AT is
not in an area where the first system can support the communication
session.
8. The method of claim 7, wherein the attempting step is only
performed if the second system is determined to be available for a
handoff.
9. The method of claim 8, wherein the attempting step is only
performed if an application-layer performance expectation of the
second system is above a performance threshold.
10. The method of claim 7, wherein the attempting step is only
performed if a priority of a user of the access terminal (AT) is
sufficient to permit using the second system for the communication
session.
11. The method of claim 1, wherein the one or more
application-layer performance parameters includes a media error
rate (MER) of the communication session supported over the first
system.
12. The method of claim 11, wherein the monitoring step includes:
determining the MER during at least a portion of the communication
session supported over the first system; comparing the determined
MER with a MER threshold; and attempting a handoff of the
communication session from the first system to the second system if
the comparison indicates that the determined MER is above the MER
threshold.
13. The method of claim 12, wherein the attempting step is only
performed if the second system is determined to be available for a
handoff.
14. The method of claim 13, wherein the attempting step is only
performed if an application-layer performance expectation of the
second system is above a performance threshold.
15. The method of claim 11, wherein the attempting step is only
performed if a priority of a user of the access terminal (AT) is
sufficient to permit using the second system for the communication
session.
16. The method of claim 1, wherein the one or more
application-layer performance parameters includes an outage
duration (OD) of the communication session supported over the first
system.
17. The method of claim 16, wherein the monitoring step includes:
determining the OD during at least a portion of the communication
session supported over the first system; comparing the determined
OD with an OD threshold; and attempting a handoff of the
communication session from the first system to the second system if
the comparison indicates that the determined OD is above the OD
threshold.
18. The method of claim 17, wherein the attempting step is only
performed if the second system is determined to be available for a
handoff.
19. The method of claim 18, wherein the attempting step is only
performed if an application-layer performance expectation of the
second system is above a performance threshold.
20. The method of claim 17, wherein the attempting step is only
performed if a priority of a user of the access terminal (AT) is
sufficient to permit using the second system for the communication
session.
21. The method of claim 1, wherein the one or more
application-layer performance parameters includes a charging rate
of the communication session supported over the first system.
22. The method of claim 21, wherein the monitoring step includes:
determining the charging rate during at least a portion of the
communication session supported over the first system; comparing
the determined charging rate with a charging rate threshold; and
attempting a handoff of the communication session from the first
system to the second system if the comparison indicates that the
determined charging is above the charging rate threshold.
23. The method of claim 21, wherein the attempting step is only
performed if the second system is determined to be available for a
handoff.
24. The method of claim 22, wherein the charging rate threshold
corresponds to a charging rate associated with conducting the
communication session over the second system.
25. The method of claim 21, wherein the attempting step is only
performed if a priority of a user of the access terminal (AT) is
sufficient to permit using the second system for the communication
session.
26. The method of claim 1, wherein the determining step includes:
if the monitoring step indicates that the one or more
application-layer performance parameters are not sufficient,
evaluating application-layer performance expectations associated
with conducting the communication system on each of a plurality of
systems other than the first system; and if the evaluating step
indicates at least one of the plurality of systems is expected to
provide better application-layer performance than the first system,
selecting one of the plurality of systems as the second system.
27. The method of claim 1, wherein the selected system corresponds
to a given system amount the plurality of system having the highest
application-layer performance expectation.
28. An access terminal configured to participate in a communication
session within a communications system, comprising: means for
participating in a communication session supported over a first
system associated with a first physical layer; means for monitoring
one or more application-layer performance parameters associated
with the communication session; means for determining, based at
least in part on the monitoring, whether to hand off the
communication session from the first system to a second system
associated with a second physical layer; and means for selectively
handing off the communication session from the first system to the
second system based on the determination.
29. An access terminal configured to participate in a communication
session within a communications system, comprising: logic
configured to participate in a communication session supported over
a first system associated with a first physical layer; logic
configured to monitor one or more application-layer performance
parameters associated with the communication session; logic
configured to determine, based at least in part on the monitoring,
whether to hand off the communication session from the first system
to a second system associated with a second physical layer; and
logic configured to selectively hand off the communication session
from the first system to the second system based on the
determination.
30. A computer-readable storage medium comprising program code,
which, when executed by an access terminal configured to
participate in a communication session within a communications
system, causes the access terminal to perform operations, the
program code comprising: program code to participate in a
communication session supported over a first system associated with
a first physical layer; program code to monitor one or more
application-layer performance parameters associated with the
communication session; program code to determine, based at least in
part on the monitoring, whether to hand off the communication
session from the first system to a second system associated with a
second physical layer; and program code to selectively hand off the
communication session from the first system to the second system
based on the determination.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the present invention are directed to an
application-layer handoff of an access terminal from a first system
of an access network to a second system of the access network
during a communication session within a wireless communications
system.
[0003] 2. Description of the Related Art
[0004] Wireless communication systems have developed through
various generations, including a first-generation analog wireless
phone service (1G), a second-generation (2G) digital wireless phone
service (including interim 2.5G and 2.75G networks) and a
third-generation (3G) high speed data/Internet-capable wireless
service. There are presently many different types of wireless
communication systems in use, including Cellular and Personal
Communications Service (PCS) systems. Examples of known cellular
systems include the cellular Analog Advanced Mobile Phone System
(AMPS), and digital cellular systems based on Code Division
Multiple Access (CDMA), Frequency Division Multiple Access (FDMA),
Time Division Multiple Access (TDMA), the Global System for Mobile
access (GSM) variation of TDMA, and newer hybrid digital
communication systems using both TDMA and CDMA technologies.
[0005] The method for providing CDMA mobile communications was
standardized in the United States by the Telecommunications
Industry Association/Electronic Industries Association in
TIA/EIA/IS-95-A entitled "Mobile Station-Base Station Compatibility
Standard for Dual-Mode Wideband Spread Spectrum Cellular System,"
referred to herein as IS-95. Combined AMPS & CDMA systems are
described in TIA/EIA Standard IS-98. Other communications systems
are described in the IMT-2000/UM, or International Mobile
Telecommunications System 2000/Universal Mobile Telecommunications
System, standards covering what are referred to as wideband CDMA
(WCDMA), CDMA2000 (such as CDMA2000 1xEV-DO standards, for example)
or TD-SCDMA.
[0006] In wireless communication systems, mobile stations,
handsets, or access terminals (AT) receive signals from fixed
position base stations (also referred to as cell sites or cells)
that support communication links or service within particular
geographic regions adjacent to or surrounding the base stations.
Base stations provide entry points to an access network (AN)/radio
access network (RAN), which is generally a packet data network
using standard Internet Engineering Task Force (IETF) based
protocols that support methods for differentiating traffic based on
Quality of Service (QoS) requirements. Therefore, the base stations
generally interact with ATs through an over the air interface and
with the AN through Internet Protocol (IP) network data
packets.
[0007] In wireless telecommunication systems, Push-to-talk (PTT)
capabilities are becoming popular with service sectors and
consumers. PTT can support a "dispatch" voice service that operates
over standard commercial wireless infrastructures, such as CDMA,
FDMA, TDMA, GSM, etc. In a dispatch model, communication between
endpoints (ATs) occurs within virtual groups, wherein the voice of
one "talker" is transmitted to one or more "listeners." A single
instance of this type of communication is commonly referred to as a
dispatch call, or simply a PTT call. A PTT call is an instantiation
of a group, which defines the characteristics of a call. A group in
essence is defined by a member list and associated information,
such as group name or group identification.
[0008] Conventionally, data packets within a wireless
communications network have been configured to be sent to a single
destination or access terminal. A transmission of data to a single
destination is referred to as "unicast". As mobile communications
have increased, the ability to transmit given data concurrently to
multiple access terminals has become more important. Accordingly,
protocols have been adopted to support concurrent data
transmissions of the same packet or message to multiple
destinations or target access terminals. A "broadcast" refers to a
transmission of data packets to all destinations or access
terminals (e.g., within a given cell, served by a given service
provider, etc.), while a "multicast" refers to a transmission of
data packets to a given group of destinations or access terminals.
In an example, the given group of destinations or "multicast group"
may include more than one and less than all of possible
destinations or access terminals (e.g., within a given group,
served by a given service provider, etc.). However, it is at least
possible in certain situations that the multicast group comprises
only one access terminal, similar to a unicast, or alternatively
that the multicast group comprises all access terminals (e.g.,
within a cell or sector), similar to a broadcast.
[0009] Broadcasts and/or multicasts may be performed within
wireless communication systems in a number of ways, such as
performing a plurality of sequential unicast operations to
accommodate the multicast group, allocating a unique
broadcast/multicast channel (BCH) for handling multiple data
transmissions at the same time and the like. A conventional system
using a broadcast channel for push-to-talk communications is
described in United States Patent Application Publication No.
2007/0049314 dated Mar. 1, 2007 and entitled "Push-To-Talk Group
Call System Using CDMA 1x-EVDO Cellular Network", the contents of
which are incorporated herein by reference in its entirety. As
described in Publication No. 2007/0049314, a broadcast channel can
be used for push-to-talk calls using conventional signaling
techniques. Although the use of a broadcast channel may improve
bandwidth requirements over conventional unicast techniques, the
conventional signaling of the broadcast channel can still result in
additional overhead and/or delay and may degrade system
performance.
[0010] The 3.sup.rd Generation Partnership Project 2 ("3GPP2")
defines a broadcast-multicast service (BCMCS) specification for
supporting multicast communications in CDMA2000 networks.
Accordingly, a version of 3GPP2's BCMCS specification, entitled
"CDMA2000 High Rate Broadcast-Multicast Packet Data Air Interface
Specification", dated Feb. 14, 2006, Version 1.0 C.S0054-A, is
hereby incorporated by reference in its entirety.
SUMMARY
[0011] Embodiments are directed to an application-layer handoff of
an access terminal from a first system of an access network to a
second system of the access network during a communication session
within a wireless communications system. In an embodiment, the
access terminal sets up a communication session on the first
system. A multimedia client measures application-layer performance
parameters for the communication session supported by the first
system, and determines whether to handoff the communication session
to a second system based at least in part on the application-layer
performance parameters. If the multimedia client determines to
handoff the communication session to the second system, the
multimedia client initiates the handoff and the communication
session is transitioned to the second system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A more complete appreciation of embodiments of the invention
and many of the attendant advantages thereof will be readily
obtained as the same becomes better understood by reference to the
following detailed description when considered in connection with
the accompanying drawings which are presented solely for
illustration and not limitation of the invention, and in which:
[0013] FIG. 1 is a diagram of a wireless network architecture that
supports access terminals and access networks in accordance with at
least one embodiment of the invention.
[0014] FIG. 2A illustrates the core network of FIG. 1 according to
an embodiment of the present invention.
[0015] FIG. 2B illustrates an example of the wireless
communications system of FIG. 1 in more detail.
[0016] FIG. 3 is an illustration of an access terminal in
accordance with at least one embodiment of the invention.
[0017] FIG. 4 illustrates a conventional inter-system handoff of a
given access terminal that is participating in a wireless
communication session.
[0018] FIG. 5 illustrates a system-handoff of a given access
terminal that is participating in a wireless communication session
in accordance with an embodiment of the invention.
[0019] FIG. 6A illustrates the system-handoff process of FIG. 5
whereby one application-layer performance parameter corresponds to
a location of the given access terminal within the wireless
communications system in accordance with an embodiment of the
invention.
[0020] FIG. 6B illustrates the system-handoff process of FIG. 5
whereby one application-layer performance parameter corresponds to
a media error rate (MER) for the given access terminal's
communication session within the wireless communications system in
accordance with an embodiment of the invention.
[0021] FIG. 6C illustrates the system-handoff process of FIG. 5
whereby one application-layer performance parameter corresponds to
an outage duration for the given access terminal's communication
session within the wireless communications system in accordance
with an embodiment of the invention.
[0022] FIG. 6D illustrates the system-handoff process of FIG. 5
whereby one application-layer performance parameter corresponds to
a current rate at which a subscriber using the given access
terminal is being charged for service related to the given access
terminal's communication session within the wireless communications
system in accordance with an embodiment of the invention.
[0023] FIG. 6E illustrates the system-handoff process of FIG. 5
whereby one or more application-layer performance parameters are
considered during a potential handoff of the given access terminal
from a first system to one of a plurality of other potential
systems during the given access terminal's communication session
within the wireless communications system in accordance with an
embodiment of the invention.
DETAILED DESCRIPTION
[0024] Aspects of the invention are disclosed in the following
description and related drawings directed to specific embodiments
of the invention. Alternate embodiments may be devised without
departing from the scope of the invention. Additionally, well-known
elements of the invention will not be described in detail or will
be omitted so as not to obscure the relevant details of the
invention.
[0025] The words "exemplary" and/or "example" are used herein to
mean "serving as an example, instance, or illustration." Any
embodiment described herein as "exemplary" and/or "example" is not
necessarily to be construed as preferred or advantageous over other
embodiments. Likewise, the term "embodiments of the invention" does
not require that all embodiments of the invention include the
discussed feature, advantage or mode of operation.
[0026] Further, many embodiments are described in terms of
sequences of actions to be performed by, for example, elements of a
computing device. It will be recognized that various actions
described herein can be performed by specific circuits (e.g.,
application specific integrated circuits (ASICs)), by program
instructions being executed by one or more processors, or by a
combination of both. Additionally, these sequence of actions
described herein can be considered to be embodied entirely within
any form of computer readable storage medium having stored therein
a corresponding set of computer instructions that upon execution
would cause an associated processor to perform the functionality
described herein. Thus, the various aspects of the invention may be
embodied in a number of different forms, all of which have been
contemplated to be within the scope of the claimed subject matter.
In addition, for each of the embodiments described herein, the
corresponding form of any such embodiments may be described herein
as, for example, "logic configured to" perform the described
action.
[0027] A High Data Rate (HDR) subscriber station, referred to
herein as an access terminal (AT), may be mobile or stationary, and
may communicate with one or more HDR base stations, referred to
herein as modem pool transceivers (MPTs) or base stations (BS). An
access terminal transmits and receives data packets through one or
more modem pool transceivers to an HDR base station controller,
referred to as a modem pool controller (MPC), base station
controller (BSC) and/or packet control function (PCF). Modem pool
transceivers and modem pool controllers are parts of a network
called an access network. An access network transports data packets
between multiple access terminals.
[0028] The access network may be further connected to additional
networks outside the access network, such as a corporate intranet
or the Internet, and may transport data packets between each access
terminal and such outside networks. An access terminal that has
established an active traffic channel connection with one or more
modem pool transceivers is called an active access terminal, and is
said to be in a traffic state. An access terminal that is in the
process of establishing an active traffic channel connection with
one or more modem pool transceivers is said to be in a connection
setup state. An access terminal may be any data device that
communicates through a wireless channel or through a wired channel,
for example using fiber optic or coaxial cables. An access terminal
may further be any of a number of types of devices including but
not limited to PC card, compact flash, external or internal modem,
or wireless or wireline phone. The communication link through which
the access terminal sends signals to the modem pool transceiver is
called a reverse link or traffic channel. The communication link
through which a modem pool transceiver sends signals to an access
terminal is called a forward link or traffic channel. As used
herein the term traffic channel can refer to either a forward or
reverse traffic channel.
[0029] FIG. 1 illustrates a block diagram of one exemplary
embodiment of a wireless system 100 in accordance with at least one
embodiment of the invention. System 100 can contain access
terminals, such as cellular telephone 102, in communication across
an air interface 104 with an access network or radio access network
(RAN) 120 that can connect the access terminal 102 to network
equipment providing data connectivity between a packet switched
data network (e.g., an intranet, the Internet, and/or carrier
network 126) and the access terminals 102, 108, 110, 112. As shown
here, the access terminal can be a cellular telephone 102, a
personal digital assistant 108, a pager 110, which is shown here as
a two-way text pager, or even a separate computer platform 112 that
has a wireless communication portal. Embodiments of the invention
can thus be realized on any form of access terminal including a
wireless communication portal or having wireless communication
capabilities, including without limitation, wireless modems, PCMCIA
cards, personal computers, telephones, or any combination or
sub-combination thereof. Further, as used herein, the terms "access
terminal", "wireless device", "client device", "mobile terminal"
and variations thereof may be used interchangeably.
[0030] Referring back to FIG. 1, the components of the wireless
network 100 and interrelation of the elements of the exemplary
embodiments of the invention are not limited to the configuration
illustrated. System 100 is merely exemplary and can include any
system that allows remote access terminals, such as wireless client
computing devices 102, 108, 110, 112 to communicate over-the-air
between and among each other and/or between and among components
connected via the air interface 104 and RAN 120, including, without
limitation, carrier network 126, the Internet, and/or other remote
servers.
[0031] The RAN 120 controls messages (typically sent as data
packets) sent to a base station controller/packet control function
(BSC/PCF) 122. The BSC/PCF 122 is responsible for signaling,
establishing, and tearing down bearer channels (i.e., data
channels) between a packet data service node 100 ("PDSN") and the
access terminals 102/108/110/112. If link layer encryption is
enabled, the BSC/PCF 122 also encrypts the content before
forwarding it over the air interface 104. The function of the
BSC/PCF 122 is well-known in the art and will not be discussed
further for the sake of brevity. The carrier network 126 may
communicate with the BSC/PCF 122 by a network, the Internet and/or
a public switched telephone network (PSTN). Alternatively, the
BSC/PCF 122 may connect directly to the Internet or external
network. Typically, the network or Internet connection between the
carrier network 126 and the BSC/PCF 122 transfers data, and the
PSTN transfers voice information. The BSC/PCF 122 can be connected
to multiple base stations (BS) or modem pool transceivers (MPT)
124. In a similar manner to the carrier network, the BSC/PCF 122 is
typically connected to the MPT/BS 124 by a network, the Internet
and/or PSTN for data transfer and/or voice information. The MPT/BS
124 can broadcast data messages wirelessly to the access terminals,
such as cellular telephone 102. The MPT/BS 124, BSC/PCF 122 and
other components may form the RAN 120, as is known in the art.
However, alternate configurations may also be used and the
invention is not limited to the configuration illustrated. For
example, in another embodiment the functionality of the BSC/PCF 122
and one or more of the MPT/BS 124 may be collapsed into a single
"hybrid" module having the functionality of both the BSC/PCF 122
and the MPT/BS 124.
[0032] FIG. 2A illustrates the carrier network 126 according to an
embodiment of the present invention. In the embodiment of FIG. 2A,
the carrier network 126 includes a packet data serving node (PDSN)
160, a broadcast serving node (BSN) 165, an application server 170
and an Internet 175. However, application server 170 and other
components may be located outside the carrier network in
alternative embodiments. The PDSN 160 provides access to the
Internet 175, intranets and/or remote servers (e.g., application
server 170) for mobile stations (e.g., access terminals, such as
102, 108, 110, 112 from FIG. 1) utilizing, for example, a cdma2000
Radio Access Network (RAN) (e.g., RAN 120 of FIG. 1). Acting as an
access gateway, the PDSN 160 may provide simple IP and mobile IP
access, foreign agent support, and packet transport. The PDSN 160
can act as a client for Authentication, Authorization, and
Accounting (AAA) servers and other supporting infrastructure and
provides mobile stations with a gateway to the IP network as is
known in the art. As shown in FIG. 2A, the PDSN 160 may communicate
with the RAN 120 (e.g., the BSC/PCF 122) via a conventional A10
connection. The A10 connection is well-known in the art and will
not be described further for the sake of brevity.
[0033] Referring to FIG. 2A, the broadcast serving node (BSN) 165
may be configured to support multicast and broadcast services. The
BSN 165 will be described in greater detail below. The BSN 165
communicates with the RAN 120 (e.g., the BSC/PCF 122) via a
broadcast (BC) A10 connection, and with the application server 170
via the Internet 175. The BCA10 connection is used to transfer
multicast and/or broadcast messaging. Accordingly, the application
server 170 sends unicast messaging to the PDSN 160 via the Internet
175, and sends multicast messaging to the BSN 165 via the Internet
175.
[0034] Generally, as will be described in greater detail below, the
RAN 120 transmits multicast messages, received from the BSN 165 via
the BCA10 connection, over a broadcast channel (BCH) of the air
interface 104 to one or more access terminals 200.
[0035] FIG. 2B illustrates an example of the wireless communication
100 of FIG. 1 in more detail. In particular, referring to FIG. 2B,
ATs 1 . . . N are shown as connecting to the RAN 120 at locations
serviced by different packet data network end-points. Accordingly,
ATs 1 and 3 connect to the RAN 120 at a portion served by a first
packet data network end-point 162 (e.g., which may correspond to
PDSN 160, BSN 165, a home agent (HA), a foreign agent (FA), etc.).
The first packet data network end-point 162 in turn connects, via
the routing unit 188, to the Internet 175 and/or to one or more of
an authentication, authorization and accounting (AAA) server 182, a
provisioning server 184, an Internet Protocol (IP) Multimedia
Subsystem (IMS)/Session Initiation Protocol (SIP) Registration
Server 186 and/or the application server 170. ATs 2 and 5 . . . N
connect to the RAN 120 at a portion served by a second packet data
network end-point 164 (e.g., which may correspond to PDSN 160, BSN
165, FA, HA, etc.). Similar to the first packet data network
end-point 162, the second packet data network end-point 164 in turn
connects, via the routing unit 188, to the Internet 175 and/or to
one or more of the AAA server 182, a provisioning server 184, an
IMS/SIP Registration Server 186 and/or the application server 170.
AT 4 connects directly to the Internet 175, and through the
Internet 175 can then connect to any of the system components
described above.
[0036] Referring to FIG. 2B, ATs 1, 3 and 5 . . . N are illustrated
as wireless cell-phones, AT 2 is illustrated as a wireless
tablet-PC and AT 4 is illustrated as a wired desktop station.
However, in other embodiments, it will be appreciated that the
wireless communication system 100 can connect to any type of AT,
and the examples illustrated in FIG. 2B are not intended to limit
the types of ATs that may be implemented within the system. Also,
while the AAA 182, the provisioning server 184, the IMS/SIP
registration server 186 and the application server 170 are each
illustrated as structurally separate servers, one or more of these
servers may be consolidated in at least one embodiment of the
invention.
[0037] Further, referring to FIG. 2B, the application server 170 is
illustrated as including a plurality of media control complexes
(MCCs) 1 . . . N 170B, and a plurality of regional dispatchers 1 .
. . N 170A. Collectively, the regional dispatchers 170A and MCCs
170B are included within the application server 170, which in at
least one embodiment can correspond to a distributed network of
servers that collectively functions to arbitrate communication
sessions (e.g., half-duplex group communication sessions via IP
unicasting and/or IP multicasting protocols) within the wireless
communication system 100. For example, because the communication
sessions arbitrated by the application server 170 can theoretically
take place between ATs located anywhere within the system 100,
multiple regional dispatchers 170A and MCCs are distributed to
reduce latency for the arbitrated communication sessions (e.g., so
that a MCC in North America is not relaying media back-and-forth
between session participants located in China). Thus, when
reference is made to the application server 170, it will be
appreciated that the associated functionality can be enforced by
one or more of the regional dispatchers 170A and/or one or more of
the MCCs 170B. The regional dispatchers 170A are generally
responsible for any functionality related to establishing a
communication session (e.g., handling signaling messages between
the ATs, scheduling and/or sending announce messages, etc.),
whereas the MCCs 170B are responsible for hosting the communication
session for the duration of the call instance, including conducting
an in-call signaling and an actual exchange of media during an
arbitrated communication session.
[0038] Referring to FIG. 3, an access terminal 200, (here a
wireless device), such as a cellular telephone, has a platform 202
that can receive and execute software applications, data and/or
commands transmitted from the RAN 120 that may ultimately come from
the carrier network 126, the Internet and/or other remote servers
and networks. The platform 202 can include a transceiver 206
operably coupled to an application specific integrated circuit
("ASIC" 208), or other processor, microprocessor, logic circuit, or
other data processing device. The ASIC 208 or other processor
executes the application programming interface ("API") 210 layer
that interfaces with any resident programs in the memory 212 of the
wireless device. The memory 212 can be comprised of read-only or
random-access memory (RAM and ROM), EEPROM, flash cards, or any
memory common to computer platforms. The platform 202 also can
include a local database 214 that can hold applications not
actively used in memory 212. The local database 214 is typically a
flash memory cell, but can be any secondary storage device as known
in the art, such as magnetic media, EEPROM, optical media, tape,
soft or hard disk, or the like. The internal platform 202
components can also be operably coupled to external devices such as
antenna 222, display 224, push-to-talk button 228 and keypad 226
among other components, as is known in the art.
[0039] Accordingly, an embodiment of the invention can include an
access terminal including the ability to perform the functions
described herein. As will be appreciated by those skilled in the
art, the various logic elements can be embodied in discrete
elements, software modules executed on a processor or any
combination of software and hardware to achieve the functionality
disclosed herein. For example, ASIC 208, memory 212, API 210 and
local database 214 may all be used cooperatively to load, store and
execute the various functions disclosed herein and thus the logic
to perform these functions may be distributed over various
elements. Alternatively, the functionality could be incorporated
into one discrete component. Therefore, the features of the access
terminal in FIG. 3 are to be considered merely illustrative and the
invention is not limited to the illustrated features or
arrangement.
[0040] The wireless communication between the access terminal 102
and the RAN 120 can be based on different technologies, such as
code division multiple access (CDMA), WCDMA, time division multiple
access (TDMA), frequency division multiple access (FDMA),
Orthogonal Frequency Division Multiplexing (OFDM), the Global
System for Mobile Communications (GSM), or other protocols that may
be used in a wireless communications network or a data
communications network. The data communication is typically between
the client device 102, MPT/BS 124, and BSC/PCF 122. The BSC/PCF 122
can be connected to multiple data networks such as the carrier
network 126, PSTN, the Internet, a virtual private network, and the
like, thus allowing the access terminal 102 access to a broader
communication network. As discussed in the foregoing and known in
the art, voice transmission and/or data can be transmitted to the
access terminals from the RAN using a variety of networks and
configurations. Accordingly, the illustrations provided herein are
not intended to limit the embodiments of the invention and are
merely to aid in the description of aspects of embodiments of the
invention.
[0041] Access terminals can be configured to connect to servers,
such as the application server 170, through one of a plurality of
systems or networks. For example, a given access terminal can
connect to the application server 170 via a WiFi system (e.g.,
802.11a/b, etc.), a CDMA2000 1x system, a Wideband CDMA (WCDMA)
system, a FDMA system, a TDMA system, a OFDM system, a long-term
evolution (LTE) system, a BCMCS system by which the RAN 120
transmits messages to multiple ATs within a given sector on a
shared downlink channel, such as a broadcast channel (BCH), a
multimedia broadcast/multicast services (MBMS) system and/or a
unicast 1x EV-DO system by which the RAN 120 transmits messages to
a single AT on a downlink dedicated channel (DCH) or unicast
channel. Accordingly, the term `system` as used herein, in the
context of providing service to an access terminal through the RAN
120, corresponds to any type of wireless technology through which
the access terminal can establish a link to other network
components, such as the application server 170.
[0042] The access terminal can setup a communication session (e.g.,
a push-to-talk (PTT) session, a VoIP session, a half-duplex
session, a full-duplex session, etc.) on a first system, and can
later switch from the first system to a second system without
terminating the communication session. This type of switch can be
referred to as an inter-system handover or handoff. An inter-system
handoff of the access terminal between systems (e.g., EV-DO, 1x,
BCMCS, cdma2000 1X, etc.) should not be confused with a handoff of
the access terminal from one serving area (e.g., a cell, sector,
subnet, etc.) to another serving area. In other words, the access
terminal can handoff from one type of system providing service to
another type of system, and the access terminal can also
(separately) handoff from one service area for a particular system
to another service area for the same system. Embodiments of the
invention are generally directed to inter-system handoff, although
this does not preclude a serving-area handoff from occurring in
conjunction with the embodiments described herein.
[0043] Handoffs of the access terminal from one system (e.g.,
BCMCS) to another system (e.g., 1x, unicast EV-DO, etc.) are
conventionally controlled at the AT with software that operates at
a lower-layer, such as the physical layer. This software construct
may be referred to as a lower layer controller, and may be stored
in memory 212 and executed by the ASIC 208. In an example, the
lower layer controller can base handoff-decisions on physical layer
parameters, such as frame-error-rate (FER), pilot signal strength,
detection of a new system, etc. Generally, this means the lower
layer controller evaluates how well packets containing data are
exchanged on a packet-by-packet or physical frame-by-frame basis,
without taking into account the higher-level or application-layer
uses of the actual data. Furthermore, inter-system handoff
generally requires complex signaling exchanges between the AT and
the RAN 120 in order to command the related measurements, report
the results, and transmit handoff commands in a seamless
manner.
[0044] FIG. 4 illustrates a conventional inter-system handoff of a
given access terminal ("AT 1") that is participating in a wireless
communication session. Referring to FIG. 4, assume that AT 1 is
configured to connect to the RAN 120 on either a first system or a
second system. For convenience of explanation, assume that the
first system corresponds to generally to EV-DO and the second
system corresponds to BCMCS.
[0045] Referring to FIG. 4, AT 1 sets up a communication session on
the first system, 400. For example, if the communication session
corresponds to a PTT session originated by AT 1, a multimedia
client 210A that is responsible for managing AT 1's PTT session at
the application-layer receives an indication that a user of AT 1
has pushed a PTT button. The multimedia client 210A then requests
the lower layer controller to schedule and send a call message to
the application server 170. After obtaining or waiting for the
requisite call resources, the lower layer controller sends the call
message to the RAN 120 (e.g., on a reverse link access channel or a
R-TCH), which is forwarded to the application server 170, which
announces the session to one or more target ATs and then sends a
floor-grant to AT 1 after at least one target AT accepts the
announced session.
[0046] While the communication session is conducted on the first
system, the lower layer controller monitors one or more lower-layer
performance parameters associated with the communication session,
405. For example, the one or more lower-layer performance
parameters may include a frame-error-rate (FER) for packets
associated with the communication session. Alternatively or
additionally, the lower layer controller may monitor a pilot signal
strength of the first system.
[0047] Based on the monitored one or more lower-layer performance
parameters, the lower layer controller determines whether to
trigger a handoff of AT 1 from the first system to the second
system, 410. For example, if the lower layer controller is
configured to make handoff decisions between systems for AT 1 based
on FER, then the decision of 410 may correspond to comparing a
current FER or running-average FER for AT 1's communication session
on the first system with a threshold FER, and then selectively
triggering a handoff if the current or running-average FER is
higher than the threshold FER.
[0048] If the lower layer controller of AT 1 determines not to
handoff to the second system in 410, the process returns to 405 and
AT 1 continues to monitor the one or more lower-layer performance
parameters while the communication system continues on the first
system. Otherwise, if the lower layer controller of AT 1 determines
to handoff to the second system in 410, the lower layer controller
initiates or triggers the handoff of AT 1 from the first system to
the second system, as is known in the art, 415. For example, if the
first system is BCMCS and the second system is unicast EV-DO, then
the handoff to the second system may include requesting a unicast
TCH and de-registering with the RAN 120 for multicast support via
BCMCS. The particular signaling that occurs to facilitate the
handoff in 415 is not shown because this signaling can be different
for handoffs between different systems of the RAN 120 (e.g., EV-DO
to 1x, BCMCS to unicast EV-DO, unicast EV-DO to WiFi, etc.). After
completing the handoff that is initiated in 415, AT 1 continues the
communication session on the second system, if possible, 420.
[0049] It should be noted that many systems do not support
inter-system lower layer signaling. Even if such systems do,
inter-system handoff is conventionally restricted to/from a
restricted set of systems. For these reasons, supporting the
inter-system handoff at the lower layer can require significant
enhancements to the existing systems. On the other hand, the
application-initiated inter-system handoff can be implemented using
existing layer signaling messages without requiring any system
enhancements. Specific mechanisms for initiating the inter-system
handoff at the application layer will be elaborated later.
[0050] As will be appreciated by one of ordinary skill in the art,
the process of FIG. 4 can potentially permit AT 1 to handoff to
another system with superior physical-layer performance
characteristics in the event of physical-layer performance
degradation on a current system. In the absence of lower layer
support, it is possible that the degraded performance related to
the communication session at the application-level and the
existence of an alternative system can trigger an
application-driven inter-system handoff. For example, the
communication session may undergo a relatively high
media-error-rate (MER) and/or outage duration (OD), which occurs at
the application-level. If the application finds availability of an
alternative/second system, the application may attempt to handoff
to the second system. In another example, if an access terminal is
supported by a system with a higher charging rate than another
available system (e.g., the AT is connected to a cellular network
and hands off to a roaming service area, a free WiFi connection
becomes available while the AT is connected to an in-network
cellular system that is costing a user thereof usage minutes,
etc.), the user thereof may wish to handoff to the cheaper system.
Accordingly, embodiments of the invention are generally directed to
making system handoff decisions based on one or more
application-layer criteria either in place of or in addition to
lower-layer (e.g., physical-layer) considerations as in FIG. 4.
[0051] FIG. 5 illustrates a system-handoff of a given access
terminal ("AT 1") that is participating in a wireless communication
session in accordance with an embodiment of the invention. In
particular, FIG. 5 illustrates the inventive inter-system handoff
process at a relatively high level, with examples of more detailed
implementations provided afterwards with respect to FIGS. 6A
through 6E. Referring to FIG. 5, assume that AT 1 is configured to
connect to the RAN 120 on at least two systems or wireless
connection technologies (e.g., EV-DO, BCMCS, 1x, WiFi, Bluetooth,
etc.).
[0052] Referring to FIG. 5, AT 1 sets up a communication session on
the first system, 500. For example, if the communication session
corresponds to a PTT session originated by AT 1, a multimedia
client 210A that is responsible for managing AT 1's PTT session at
the application-layer receives an indication that a user of AT 1
has pushed a PTT button. The multimedia client 210A then requests
the lower layer controller to schedule and send a call message to
the application server 170. After obtaining or waiting for the
requisite call resources, the lower layer controller sends the call
message to the RAN 120 (e.g., on a reverse link access channel or a
R-TCH), which is forwarded to the application server 170, which
announces the session to one or more target ATs and then sends a
floor-grant to AT 1 after at least one target AT accepts the
announced session.
[0053] While not illustrated in FIG. 5, while the communication
session is conducted on the first system, the lower layer
controller can monitor one or more lower-layer performance
parameters associated with the communication session as in FIG. 4,
and the lower layer controller can initiate handoffs based on the
lower-layer or physical-layer performance of the different systems.
However, in FIG. 5, performance at the physical-layer need not be
the only type of performance considered in determining whether to
handoff from one system to another.
[0054] Accordingly, the multimedia client 210A measures one or more
application-layer performance parameters for the communication
system that is being supported by the first system of the RAN 120,
505. For example, the one or more application-layer performance
parameters can include (i) a media-error-rate (MER) of the
communication session (e.g., based on a success rate of audio
frames if the communication session is an audio session, based on a
success rate of video and/or audio frames if the communication
session is a video conference), (ii) an outage duration (OD) of the
communication session (e.g., a period of downlink inactivity due to
successive media errors on the communication session), (iii) a rate
at which the first system is currently charging a user of AT 1 for
usage related to the communication session), (iv) the multimedia
client's 210A status as floor-holder or listener if the
communication corresponds to a half-duplex PTT session, (v) a
priority of the user of AT 1 (e.g., such that a priority of a user
of AT 1 is evaluated, and a handoff to a system with superior
application-layer performance is only performed if the user's
priority is sufficient to permit using the target system for a
current application), and/or (vi) any combination thereof.
[0055] Based on the monitored one or more application-layer
performance parameters, the multimedia client 210A determines
whether to trigger a handoff of AT 1 from the first system to the
second system, 510. The determination of 510 may not only be based
upon the application-layer performance parameter(s) for the
communication session on the first system, but can also be based on
the availability of one or more other systems, an expected
application-layer performance of any available systems, etc.
Examples of the application-layer system handoff decision block of
510 are given below with respect to FIGS. 6A through 6E.
[0056] If the multimedia client 210A of AT 1 determines not to
handoff to the second system in 510, the process returns to 505 and
AT 1 continues to monitor the one or more lower-layer performance
parameters while the communication system continues on the first
system. Otherwise, if the multimedia client 210A of AT 1 determines
to handoff to the second system in 510, the multimedia client 210A
initiates or triggers the handoff of AT 1 from the first system to
the second system, as is known in the art, 515. In general, the
signaling that occurs to facilitate the handoff in 515 includes
releasing the connection with the first system and establishing the
connection with the second system. This is not shown explicitly in
FIG. 5 because this signaling can be different for different
systems of the RAN 120 (e.g., EV-DO to 1x, BCMCS to unicast EV-DO,
unicast EV-DO to WiFi, etc.). After completing the handoff that is
initiated in 515, AT 1 continues the communication session on the
second system, if possible, 520.
[0057] As will be appreciated by one of ordinary skill in the art
from a review of FIG. 5, the multimedia client 210A has access to
higher-level information regarding the communication session as
compared to the lower layer controller. As such, the multimedia
client 210A can potentially be in a better position to evaluate
whether a system handoff is called for by taking into account
performance of the communication session at the application layer,
and not merely the physical layer. More detailed implementation
examples of the process of FIG. 5 will now be provided with respect
to FIGS. 6A through 6E.
[0058] FIG. 6A illustrates the system-handoff process of FIG. 5
whereby one application-layer performance parameter corresponds to
a location of AT 1 within the wireless communications system 10 in
accordance with an embodiment of the invention.
[0059] Referring to FIG. 6A, AT 1 sets up a communication session
on the first system, 600A, as described above with respect to 500
of FIG. 5. In 605A, the multimedia client 210A determines location
information associated with AT 1. The location information may
correspond to a base station currently serving AT 1, a geographic
coordinate of AT 1 (e.g., a GPS coordinate), and/or any other
manner of identifying AT 1's location. In 610A, the multimedia
client 210A compares AT 1's location information with a defined
location region of the system 10. In an example, the defined
location region corresponds to a list of sectors, such that if AT
1's current sector from 605A is in the list of sectors the
multimedia client 210A can infer whether a particular system (e.g.,
unicast EV-DO, BCMCS, etc.) is available and/or permitted for use
by AT 1. Defined location regions and methodologies for determining
location information is described in more detail within co-pending
U.S. Provisional Patent Application No. 61/163,834, entitled
"REGULATING THE SCOPE OF SERVICE GEOGRAPHICALLY IN WIRELESS
NETWORKS", filed on Mar. 26, 2009, assigned to the same assignee of
the subject application, and hereby incorporated by reference in
its entirety.
[0060] Accordingly, in the example of FIG. 6A, the one or more
measured application-layer performance parameters includes some
type of location information associated with AT 1. If the location
comparison of 610A indicates that AT 1 is inside of or outside of
the defined location region, the multimedia client 210A may
determine whether to attempt a handoff to another system. For
example, the defined location region may indicate sectors that are
configured to support AT 1's communication session on the first
system, such that if AT 1 now determines itself to be outside of
the defined location region, the multimedia client 210A knows that
a handoff to another system needs to be made or else the
communication session is going to be dropped. In another example,
the defined location region may indicate sectors where a more
desirable system ("second system") than the first system is
available for supporting AT 1's communication session. In a further
example, the first system may correspond to BCMCS for supporting a
group communication session via IP multicasting protocols within
the EV-DO network of the RAN 120, and the second system may
correspond to unicast EV-DO for supporting the group communication
session via IP unicasting protocols within the EV-DO network of the
RAN 120 (or vice versa).
[0061] Based on the relationship between AT 1's location
information from 605A and the defined location region, the
multimedia client 210A either continues to monitor the location of
AT 1 during the communication session on the first system and
returns to 605A, or else advances to 615A. In 615A, AT 1 determines
whether a second system is available for supporting AT 1's
communication session with a level of application-layer performance
expected to be higher than the first system. In an example, the
presence of the second system can be inferred from AT 1's
relationship to the defined location region. If no second system is
determined to be available for supporting AT 1's communication
session in 615A, the process returns to 605A and AT 1 continues to
monitor AT 1's location during the communication session on the
first system. Otherwise, if the second system associated with a
higher expected level of application-layer performance is
determined to be available in 615A, the multimedia client 210A
initiates or triggers the handoff of AT 1 from the first system to
the second system, as is known in the art, 620A. After completing
the handoff that is initiated in 620A, AT 1 continues the
communication session on the second system, if possible, 625A.
Accordingly, the embodiment of FIG. 6A illustrates one manner by
which location of an access terminal can be used to determine when
to perform inter-system handoffs of the access terminal.
[0062] Referring to FIG. 6A, each time AT 1 re-determines its
location of AT 1 in 605A, the decision logic associated with blocks
610A and 615A may use AT 1's newly acquired location to determine
whether or not to perform an inter-system handoff. In an example,
each iteration of AT 1 determining its location can be timer-based
(i.e., performed at a given period), or event based, or a
combination thereof. In an example, events that may trigger AT 1 to
determine its location may include a media-error-rate (MER) for the
communication session on a current system rising above a threshold,
when AT 1 hands off to a new cell or sector (e.g., such as when a
Broadcast Multicast Service (BCMCS) flow status reported by AT 1
becoming unavailable as the AT enters a sector that does not
broadcast the desired BCMCS flow) and/or any other potential event
that has the potential to affect system performance and/or
availability.
[0063] FIG. 6B illustrates the system-handoff process of FIG. 5
whereby one application-layer performance parameter corresponds to
a media error rate (MER) for AT 1's communication session within
the wireless communications system 10 in accordance with an
embodiment of the invention.
[0064] Referring to FIG. 6B, AT 1 sets up a communication session
on the first system, 600B, as described above with respect to 500
of FIG. 5. In 605B, the multimedia client 210A monitors the MER for
the communication session on the first system. For example, the
monitored MER may correspond to a time-averaged indication of the
number of errors experienced by the multimedia client 210A. As will
be appreciated by one of ordinary skill in the art, the MER differs
from the FER because the FER is measured at the physical-layer,
whereas the MER is measured at the application-layer. Thus, the MER
is based on whether errors are experienced in the actual media
being played by the multimedia client 210A on AT 1, for example,
whereas the FER is based on frame-decoding errors of individual
transport packets.
[0065] After determining the MER for the communication session on
the first system in 605B, the multimedia client 210A compare AT 1
MER with an MER threshold, 610B. If AT 1's MER is determined to be
lower than the MER threshold in 610B, the process returns to 605B
and the multimedia client 210A continues to monitor the MER during
the communication session on the first system. Otherwise, if AT 1's
MER is determined to be greater than or equal to the MER threshold
in 610B, AT 1 determines whether a second system is available for
supporting AT communication session with a level of
application-layer performance expected to be higher than the first
system, 615B. In the example of FIG. 6B, this means a system that
is expected to provide a MER that is lower than the MER threshold,
or at least lower than the MER associated with the first system for
AT 1's communication session.
[0066] If no second system is determined to be available for
supporting AT 1's communication session in 615B, the process
returns to 605B and AT 1 continues to monitor the MER during the
communication session on the first system. Otherwise, if the second
system associated with a higher expected level of application-layer
performance is determined to be available in 615B, the multimedia
client 210A initiates or triggers the handoff of AT 1 from the
first system to the second system, as is known in the art, 620B.
After completing the handoff that is initiated in 620B, AT 1
continues the communication session on the second system, if
possible, 625B. Accordingly, the embodiment of FIG. 6B illustrates
one manner by which MER can be used to determine when to perform
inter-system handoffs of the access terminal.
[0067] FIG. 6C illustrates the system-handoff process of FIG. 5
whereby one application-layer performance parameter corresponds to
an outage duration for AT 1's communication session within the
wireless communications system 10 in accordance with an embodiment
of the invention.
[0068] Referring to FIG. 6C, AT 1 sets up a communication session
on the first system, 600C, as described above with respect to 500
of FIG. 5. In 605C, the multimedia client 210A monitors the OD for
the communication session on the first system. For example, the
monitored OD may correspond to a period during which media
associated with the communication session is not received from the
first system of the RAN 120. In a further example, the OD may
correspond to a timer that is reset after each successful
application-layer media frame is output by multimedia client 210A
(e.g., a video frame, an audio frame, etc.).
[0069] After determining the OD for the communication session on
the first system in 605C, the multimedia client 210A compare AT 1's
OD with an OD threshold, 610C. If AT 1's OD is determined to be
lower than the OD threshold in 610C, the process returns to 605C
and the multimedia client 210A continues to monitor the OD during
the communication session on the first system. Otherwise, if AT 1's
OD is determined to be greater than or equal to the OD threshold in
610C, AT 1 determines whether a second system is available for
supporting AT 1's communication session with a level of
application-layer performance expected to be higher than the first
system, 615C. In the example of FIG. 6C, this means a system that
is expected to provide an OD that is lower than the OD threshold,
or at least lower than the OD associated with the first system for
AT 1's communication session.
[0070] If no second system is determined to be available for
supporting AT 1's communication session in 615C, the process
returns to 605C and AT 1 continues to monitor the OD during the
communication session on the first system. Otherwise, if the second
system associated with a higher expected level of application-layer
performance is determined to be available in 615C, the multimedia
client 210A initiates or triggers the handoff of AT 1 from the
first system to the second system, as is known in the art, 620C.
After completing the handoff that is initiated in 620C, AT 1
continues the communication session on the second system, if
possible, 625C. Accordingly, the embodiment of FIG. 6C illustrates
one manner by which OD can be used to determine when to perform
inter-system handoffs of the access terminal.
[0071] FIG. 6D illustrates the system-handoff process of FIG. 5
whereby one application-layer performance parameter corresponds to
a current rate at which a subscriber using AT 1 is being charged
for service related to AT 1's communication session within the
wireless communications system 10 in accordance with an embodiment
of the invention.
[0072] Referring to FIG. 6D, AT 1 sets up a communication session
on the first system, 600D, as described above with respect to 500
of FIG. 5. In 605D, the multimedia client 210A monitors the current
rate at which the subscriber using AT 1 is being charged for
service related for the communication session on the first system.
For example, if the first system corresponds to the subscriber's
home WiFi network which is configured to provide unlimited service
for a fixed rate, than the charging rate for AT 1's communication
session on the first system may be interpreted as zero. In another
example, if the first system corresponds to the subscriber's 1x
cellular provider which is configured to provide a certain number
of minutes and afterwards charge a fee-per-minute of usage, the
charging rate for AT 1's communication session on the first system
may be interpreted as either a monetary equivalent of a minute of
usage or the fee-per-minute, dependent on how much usage the
subscriber has incurred. As will be appreciated, different metering
plans associated with system-connectivity mean that the monitored
charging rate of 605D can correspond to any of various manners by
which subscribers are charged for service.
[0073] After determining the charging rate for the communication
session on the first system in 605D, the multimedia client 210A
compare AT 1's charging rate with a charging rate threshold, 610D.
If AT 1's charging rate is determined to be lower than the charging
rate threshold in 610D, the process returns to 605D and the
multimedia client 210A continues to monitor the charging rate
during the communication session on the first system. Otherwise, if
AT 1's charging rate is determined to be greater than or equal to
the charging rate threshold in 610D, AT 1 determines whether a
second system is available for supporting AT 1's communication
session with a level of application-layer performance expected to
be higher than the first system, 615D. In the example of FIG. 6D,
this means a system that is expected to provide a charging rate
that is lower than the charging rate threshold, or at least lower
than the charging rate associated with the first system for AT 1's
communication session. For example, if the second system is a BCMCS
system that is broadcasting a certain multicast session that the AT
has been monitoring in the first system using a dedicated channel
(e.g., in EV-DO or 1x), the charging rate of the second system will
be cheaper. In an example, the charging rate threshold need not
actually be used, and the process of FIG. 6D can rather advance
directly to FIG. 6D where AT 1's current charging rate is simply
compared against the charging rate(s) of one or more other
available systems.
[0074] If no second system is determined to be available for
supporting AT 1's communication session in 615D, the process
returns to 605D and AT 1 continues to monitor the charging rate
during the communication session on the first system. Otherwise, if
the second system associated with a higher expected level of
application-layer performance is determined to be available in
615D, the multimedia client 210A initiates or triggers the handoff
of AT 1 from the first system to the second system, as is known in
the art, 620D. After completing the handoff that is initiated in
620D, AT 1 continues the communication session on the second
system, if possible, 625D. Accordingly, the embodiment of FIG. 6D
illustrates one manner by which charging rates can be used to
determine when to perform inter-system handoffs of the access
terminal.
[0075] In the embodiments of FIGS. 6A through 6D, handoffs between
a first system and a second system are described as being based on
different application-layer performance parameters. While each of
FIGS. 6A through 6D are described with respect to one particular
application-layer performance parameter, it will be appreciated
that multiple application-layer performance parameters can be
considered with regard to any system handoff decision at AT 1. For
example, two or more of OD, MER, location and/or a current charging
rate may be considered in a decision with regard to whether to
handoff to another system, with a network operator or user of AT 1
establishing which application-layer performance parameter has
priority over other parameters. Thus, if any of the designated
application-layer performance parameters degrades during AT 1's
communication session, a handoff to another system may potentially
be triggered so long as superior performance is expected at least
with the regard to the degraded parameter (e.g., with at least a
threshold amount of performance expected for each other parameter
of equal or higher priority than the degraded parameter).
[0076] Further, FIGS. 6A through 6D are each described with respect
to two particular systems; namely, AT 1's current system ("first
system") and a prospective system ("second system") under
consideration for a potential handoff. However, it is possible that
multiple systems are available for handoff from the first system.
In this case, each available system may be evaluated during a
handoff decision, as described below with respect to FIG. 6E.
[0077] FIG. 6E illustrates the system-handoff process of FIG. 5
whereby one or more application-layer performance parameters are
considered during a potential handoff of AT 1 from a first system
(e.g., system 1) to one of a plurality of other potential systems
(e.g., systems 2 . . . N, where N>2) during AT 1's communication
session within the wireless communications system 10 in accordance
with an embodiment of the invention.
[0078] Referring to FIG. 6E, AT 1 sets up a communication session
on the first system, 600E, as described above with respect to 500
of FIG. 5. In 605E, the multimedia client 210A monitors one or more
application-layer performance parameters for AT 1's communication
session on the first system (e.g., OD, MER, charging rate,
location, any combination thereof, etc.). After determining or
measuring the one or more application-layer performance parameters
for AT 1's communication session on the first system, the
multimedia client 210A determines whether the determined parameters
indicate that performance on the first system is sufficient for AT
1's communication session, 610E. If the first system is determined
by the multimedia client 210A to provide adequate performance, the
process returns to 605E and AT 1 continues to monitor the
application layer performance parameters while the communication
session continues on the first system. Otherwise, if the first
system is determined by the multimedia client 210A not to provide
adequate performance, the multimedia client 210A determines an
expectation of performance for AT 1's communication session on each
of a plurality of systems 2 . . . N, 615E. For example, if the
application-layer performance parameters include a charging rate
for the communication session, the multimedia client 210A can
determine how much the subscriber using AT 1 would be charged on
each of systems 2 . . . N. In another example, if the
application-layer performance parameters include AT 1's location,
the multimedia client 210A can determine which of systems 2 . . . n
are available and/or a degree of performance based on AT 1's
location, and so on.
[0079] In 620E, the multimedia client 210A determines a system
among systems 2 . . . N associated with a highest performance
expectation. In an example, it is possible that a given system
among systems 2 . . . N has a higher performance expectation for
one parameter and a lower performance expectation for another
parameter. In this case, each performance parameter can be assigned
a weight (e.g., as in an objective function) and a combined
performance valuation can be computed, with the highest combined
performance valuation corresponding to the system that is, overall,
expected to provide a highest level of performance.
[0080] Next, in 625E, the multimedia client 210A determines whether
the highest-rated system from 620E is expected to provide better
performance than the first system that AT 1 is currently using for
support of its communication session. If the highest-rated system
among systems 2 . . . N is not expected to provide better
performance than the first system, the process returns to 605E and
AT 1 continues to monitor the application layer performance
parameters while the communication session continues on the first
system. Otherwise, if the highest-rated system among systems 2 . .
. N is expected to provide better performance than the first
system, the multimedia client 210A initiates or triggers the
handoff of AT 1 from the first system to the highest-rated system
among systems 2 . . . N, as is known in the art, 630E. After
completing the handoff that is initiated in 630E, AT 1 continues
the communication session on its new system, if possible, 635E.
[0081] Those of skill in the art will appreciate that information
and signals may be represented using any of a variety of different
technologies and techniques. For example, data, instructions,
commands, information, signals, bits, symbols, and chips that may
be referenced throughout the above description may be represented
by voltages, currents, electromagnetic waves, magnetic fields or
particles, optical fields or particles, or any combination
thereof.
[0082] Further, those of skill in the art will appreciate that the
various illustrative logical blocks, modules, circuits, and
algorithm steps described in connection with the embodiments
disclosed herein may be implemented as electronic hardware,
computer software, or combinations of both. To clearly illustrate
this interchangeability of hardware and software, various
illustrative components, blocks, modules, circuits, and steps have
been described above generally in terms of their functionality.
Whether such functionality is implemented as hardware or software
depends upon the particular application and design constraints
imposed on the overall system. Skilled artisans may implement the
described functionality in varying ways for each particular
application, but such implementation decisions should not be
interpreted as causing a departure from the scope of the present
invention.
[0083] The various illustrative logical blocks, modules, and
circuits described in connection with the embodiments disclosed
herein may be implemented or performed with a general purpose
processor, a digital signal processor (DSP), an application
specific integrated circuit (ASIC), a field programmable gate array
(FPGA) or other programmable logic device, discrete gate or
transistor logic, discrete hardware components, or any combination
thereof designed to perform the functions described herein. A
general purpose processor may be a microprocessor, but in the
alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also
be implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0084] The methods, sequences and/or algorithms described in
connection with the embodiments disclosed herein may be embodied
directly in hardware, in a software module executed by a processor,
or in a combination of the two. A software module may reside in RAM
memory, flash memory, ROM memory, EPROM memory, EEPROM memory,
registers, hard disk, a removable disk, a CD-ROM, or any other form
of storage medium known in the art. An exemplary storage medium is
coupled to the processor such that the processor can read
information from, and write information to, the storage medium. In
the alternative, the storage medium may be integral to the
processor. The processor and the storage medium may reside in an
ASIC. The ASIC may reside in a user terminal (e.g., access
terminal). In the alternative, the processor and the storage medium
may reside as discrete components in a user terminal.
[0085] In one or more exemplary embodiments, the functions
described may be implemented in hardware, software, firmware, or
any combination thereof. If implemented in software, the functions
may be stored on or transmitted over as one or more instructions or
code on a computer-readable medium. Computer-readable media
includes both computer storage media and communication media
including any medium that facilitates transfer of a computer
program from one place to another. A storage media may be any
available media that can be accessed by a computer. By way of
example, and not limitation, such computer-readable media can
comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage,
magnetic disk storage or other magnetic storage devices, or any
other medium that can be used to carry or store desired program
code in the form of instructions or data structures and that can be
accessed by a computer. Also, any connection is properly termed a
computer-readable medium. For example, if the software is
transmitted from a website, server, or other remote source using a
coaxial cable, fiber optic cable, twisted pair, digital subscriber
line (DSL), or wireless technologies such as infrared, radio, and
microwave, then the coaxial cable, fiber optic cable, twisted pair,
DSL, or wireless technologies such as infrared, radio, and
microwave are included in the definition of medium. Disk and disc,
as used herein, includes compact disc (CD), laser disc, optical
disc, digital versatile disc (DVD), floppy disk and blu-ray disc
where disks usually reproduce data magnetically, while discs
reproduce data optically with lasers. Combinations of the above
should also be included within the scope of computer-readable
media.
[0086] While the foregoing disclosure shows illustrative
embodiments of the invention, it should be noted that various
changes and modifications could be made herein without departing
from the scope of the invention as defined by the appended claims.
The functions, steps and/or actions of the method claims in
accordance with the embodiments of the invention described herein
need not be performed in any particular order. Furthermore,
although elements of the invention may be described or claimed in
the singular, the plural is contemplated unless limitation to the
singular is explicitly stated.
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