U.S. patent application number 09/916047 was filed with the patent office on 2003-01-30 for system and method for frame selection in ip-based cdma network.
Invention is credited to Daley, Robert S., Marshall, Maria, Vassilovski, Dan.
Application Number | 20030021260 09/916047 |
Document ID | / |
Family ID | 25436623 |
Filed Date | 2003-01-30 |
United States Patent
Application |
20030021260 |
Kind Code |
A1 |
Daley, Robert S. ; et
al. |
January 30, 2003 |
System and method for frame selection in IP-based CDMA network
Abstract
A wireless telephone without IP capability nonetheless
communicates with an infrastructure that uses IP. Virtual IP
endpoints such as base stations (BTS) not only communicate with the
infrastructure using IP and with the telephone using over-the-air
protocol such as CDMA, but one of the endpoints also selects the
best frame over a call received by multiple endpoints, alleviating
the need for a base station controller (BSC) in the infrastructure.
A handoff assist entity causes frame selection to be transferred to
a second BTS in accordance with a handoff algorithm.
Inventors: |
Daley, Robert S.; (Del Mar,
CA) ; Vassilovski, Dan; (Del Mar, CA) ;
Marshall, Maria; (Oceanside, CA) |
Correspondence
Address: |
Qualcomm Incorporated
Patents Department
5775 Morehouse Drive
San Diego
CA
92121-1714
US
|
Family ID: |
25436623 |
Appl. No.: |
09/916047 |
Filed: |
July 25, 2001 |
Current U.S.
Class: |
370/352 ;
370/356 |
Current CPC
Class: |
H04B 7/2628 20130101;
H04L 12/66 20130101; H04L 65/1101 20220501 |
Class at
Publication: |
370/352 ;
370/356 |
International
Class: |
H04L 012/66 |
Claims
We claim:
1. A voice over Internet (VOIP) system, comprising: plural access
points communicating with plural wireless communication devices
using a wireless communication device over-the-air protocol
different from Internet protocol (IP), each wireless communication
device transmitting frames of information, at least a first access
point undertaking selection functionality including frame selection
and handoff control.
2. The system of claim 1, wherein the selection functionality is
undertaken for at least a first communication device, and at least
a second access point assumes frame selection for the first
communication device when a predetermined threshold is reached.
3. The system of claim 2, wherein the wireless communication device
protocol is a code division multiple access (CDMA) protocol, and
each first and second access point is a respective first and second
CDMA access point (CAP).
4. The system of claim 2, wherein the access point is a base
station (BTS).
5. The system of claim 2, wherein the infrastructure does not
include a base station controller (BSC) external to any access
point and communicating therewith.
6. The system of claim 2, comprising a selector entity in
communication with the CAPs.
7. The system of claim 6, wherein the selector entity receives
first communication device frames from the first CAP when a first
threshold is reached, the selector entity monitoring frame
selection by the first CAP for the first communication device.
8. The system of claim 7, wherein the selector entity assumes frame
selection for the first communication device when a second
threshold is reached, the second CAP proposing frame selections for
the first communication device and forwarding the frame selections
to the selector entity for monitoring thereby.
9. The system of claim 8, wherein the selector entity determines
whether frame selections from the second CAP are within a
predetermined correctness threshold, and if so, causing the second
CAP to assume frame selection for the first communication
device.
10. A method for frame selection in a wireless communication device
infrastructure, comprising: establishing communication between at
least a first base station (BTS) and at least one wireless
communication device using a non-Internet protocol (IP)
over-the-air (OTA) protocol, the first base station being one of a
plurality of base stations in an infrastructure; selecting frames
from the wireless communication device at the first base station
(BTS); then selecting frames from the wireless communication device
at a second base station (BTS).
11. The method of claim 10, further comprising: receiving first
communication device frames from the first BTS at a selector entity
when a first threshold is reached.
12. The method of claim 11, further comprising: monitoring frame
selection by the first BTS for the first communication device at
the selector entity.
13. The method of claim 12, further comprising: assuming frame
selection for the first communication device at the selector entity
when a second threshold is reached.
14. The method of claim 13, further comprising: proposing frame
selections for the first communication device at the second BTS;
and forwarding the frame selections to the selector entity for
monitoring thereby.
15. The method of claim 14, further comprising determining whether
frame selections from the second BTS are within a predetermined
correctness threshold.
16. The method of claim 15, further comprising causing the second
BTS to assume frame selection for the first communication device
when frame selections from the second BTS are within a
predetermined correctness threshold.
17. A computer program product, comprising: means for dynamically
establishing a selector base station (BTS) in a wireless telephony
infrastructure, the infrastructure using IP; means for establishing
CDMA over-the-air communication between at least one base station
in the infrastructure and a CDMA wireless communication device; and
means for handing off the selecting of frames of information from
the communication device from the selector base station to a
substitute base station upon reaching a threshold.
18. The product of claim 17, wherein the means for handing off
causes the substitute base station to assume frame selection for
the first communication device when frame selections from the
substitute base station are within a predetermined correctness
threshold. The product of claim 18, further comprising means for
receiving first communication device frames from the selector base
station at a selector entity when a first threshold is reached.
20. The product of claim 19, further comprising: means for
monitoring frame selection by the selector base station for the
first communication device at the selector entity.
21. The product of claim 20, further comprising: means for assuming
frame selection for the first communication device at the selector
entity when a second threshold is reached.
22. The product of claim 21, further comprising: means for
proposing frame selections for the first communication device at
the substitute base station; and means for forwarding the frame
selections to the selector entity for monitoring thereby.
23. The product of claim 22, further comprising means for
determining whether frame selections from the substitute base
station are within a predetermined correctness threshold.
24. A communication system, comprising: at least two communication
endpoints configured for CDMA communication with a wireless
communication device; the endpoints communicating with each other
using IP; at least a first one of the endpoints being dynamically
selected as a selector endpoint; the selector endpoint undertaking
a frame selection service for the wireless communication device;
and a selector entity transferring frame selection from the
selector endpoint to a substitute endpoint in accordance with a
handoff algorithm.
25. The system of claim 24, wherein the handoff algorithm includes:
receiving first communication device frames from the selector
endpoint at a selector entity when a first threshold is
reached.
26. The system of claim 25, wherein the algorithm further
comprises: monitoring frame selection by the selector endpoint for
the first communication device at the selector entity.
27. The system of claim 26, wherein the algorithm further
comprises: assuming frame selection for the first communication
device at the selector entity when a second threshold is
reached.
28. The system of claim 27, wherein the algorithm further
comprises: proposing frame selections for the first communication
device at the substitute endpoint; and forwarding the frame
selections to the selector entity for monitoring thereby.
29. The system of claim 28, wherein the algorithm further comprises
determining whether frame selections from the substitute endpoint
are within a predetermined correctness threshold.
30. The system of claim 29, wherein the algorithm further comprises
causing the substitute endpoint to assume frame selection for the
first communication device when frame selections from the
substitute endpoint are within a predetermined correctness
threshold.
31. A voice over Internet (VOIP) system, comprising: plural access
points communicating with plural wireless communication devices
using a wireless communication device over-the-air protocol
different from Internet protocol (IP), each wireless communication
device transmitting frames of information, at least one access
point undertaking frame selection, including the addition and
subtraction of access point sectors to a call.
32. The system of claim 31, wherein the wireless communication
device protocol is a code division multiple access (CDMA) protocol,
and each access point is a CDMA access point (CAP).
33. The system of claim 31, wherein the access point is a base
station (BTS).
34. The system of claim 31, wherein the infrastructure does not
include a base station controller (BSC) external to any access
point and communicating therewith.
35. The system of claim 31, wherein the access point converts OTA
protocol packets to IP packets.
36. The system of claim 31, wherein the access point converts IP
packets to OTA protocol packets.
37. The system of claim 31, wherein the access point is a first
access point, and the first access point directs at least a second
access point in the infrastructure to forward, to the first access
point, reverse-link frames received by the second access point from
the wireless communication device.
38. The system of claim 31, wherein the access point is a first
access point, and the first access point sends to at least a second
access point in the infrastructure forward link frames to be sent
by the second access point to the communication device.
39. The system of claim 31, wherein the access point is a first
access point, and the first access point is dynamically established
from among the plural access points.
40. A method for frame selection in a wireless communication device
infrastructure, comprising: establishing communication between at
least a first base station (BTS) and at least one wireless
communication device using a non-Internet protocol (IP)
over-the-air (OTA) protocol, the first base station being one of a
plurality of base stations in an infrastructure, wherein no base
station communicates with a base station controller (BSC) external
to a base station; selecting frames from the wireless communication
device at the first base station (BTS).
41. The method of claim 40, wherein the selecting act includes
dynamically establishing base station sectors during a call.
42. The method of claim 41, further comprising: directing, at the
first base station, at least a second base station to forward, to
the first base station, reverse-link frames received by the second
base station from the wireless communication device.
43. The method of claim 41, further comprising: sending, from the
first base station to at least a second base station, reverse-link
frames received by the first base station from the wireless
communication device.
44. The method of claim 40, further comprising dynamically
determining a frame selector base station from among the plurality
of base stations.
45. The method of claim 40, wherein at least one base station
converts OTA protocol packets to IP packets and IP packets to OTA
protocol packets.
46. The method of claim 40, comprising communicating within the
infrastructure using IP.
47. The system of claim 1, wherein the wireless communication
device is assigned a first IP address corresponding to a first
access point and a second IP address corresponding to a second
access point.
48. The method of claim 10, comprising assigning the wireless
communication device a first IP address corresponding to the first
base station and a second IP address corresponding to the second
base station.
49. The product of claim 17, further comprising: means for
assigning the communication device a first IP address corresponding
to the selector base station and a second IP address corresponding
to the substitute base station.
50. The system of claim 24, wherein the wireless communication
device is assigned a first IP address corresponding to the selector
endpoint and a second IP address corresponding to the substitute
endpoint.
Description
I. FIELD OF THE INVENTION
[0001] The present invention relates generally to enabling a
wireless telephone that is not required or generally configured to
support voice over Internet Protocols (VOIP) to nonetheless
communicate with wireless telephone infrastructure that uses IP
structures or architectures, with IP-based communication between
the wireless telephone infrastructure and any VOIP-based
infrastructure being supported.
II. BACKGROUND OF THE INVENTION
[0002] Wireless telephones, such as but not limited to wireless
telephones that communicate using Code Division Multiple Access
(CDMA) spread spectrum modulation techniques, communicate over the
air with system infrastructure using wireless telephone
over-the-air communication protocols, e.g., the CDMA protocols
known as IS-95A, IS-95B, and IS-2000. The system infrastructure,
which can include base stations (BTS), base station controllers
(BSC), and other components, connects the wireless telephone to
another communication device, such as a through land line or
another wireless communication system.
[0003] In the case of CDMA, voice data is sent over the air in
packets that are collected by the infrastructure and assembled into
a voice stream, transparently to the speakers who are talking to
each other. As might be expected, the over-the-air protocol is
tailored to optimize wireless communication. For instance, to
maximize over-the-air capacity, the over-the-air protocol contains
a minimum of signalling information, and the size of a voice data
packet is relatively small.
[0004] With the growth of the Internet, computer-to-computer
communication using Internet Protocols (IP) has become ubiquitous.
Furthermore, it has become desirable not only to facilitate
computer data communication using IP, but to facilitate voice
communication using IP as well. As but one advantage afforded by
using IP in a telephony infrastructure, much hardware such as
switches can be eliminated, and existing computers and software can
be used instead, reducing cost. To this end, so-called voice over
IP (VOIP) has been introduced.
[0005] To support VOIP, a communication device must have, among
other requirements, IP capability, i.e., the device must itself be
able to communicate using IP, and it must have an IP address.
[0006] The present invention critically observes, however, that
requiring a wireless telephone to use VOIP diminishes over-the-air
capacity because VOIP is not necessarily designed to maximize such
capacity. Instead, VOIP accounts for design considerations that are
not necessarily related to wireless telephony. As an example, the
data packet size of VOIP is relatively large, compared to the
packet size used throughout the wireless communication industry
such as in wireless telephones using over-the-air protocols such as
IS-95. Indeed, a typical packet size in the IS-95 protocol is less
than the size of a single packet header employed in a typical IP.
Moreover, configuring a wireless telephone to communicate using
both IP and over-the-air protocols complicates telephone design,
adversely strains available resources (e.g., power, computing
cycles, coding, and so on), and increases costs.
[0007] Nonetheless, the present invention understands that it would
be desirable to enable wireless telephone communication using an
infrastructure that transmits data in accordance with IP
principles. With the above considerations in mind, the present
invention provides the solutions disclosed below.
SUMMARY OF THE INVENTION
[0008] A voice over Internet (VOIP) system includes plural access
points communicating with wireless communication devices using a
wireless communication device over-the-air protocol that is
different from Internet protocol (IP). Each wireless communication
device transmits frames of information, and a first access point
undertakes frame selection for a first communication device. A
second access point assumes frame selection for the first
communication device when a predetermined threshold is reached.
[0009] In a preferred embodiment, the wireless communication device
protocol is a code division multiple access (CDMA) protocol, and
each first and second access point is a respective first and second
CDMA access point (CAP). In a particularly preferred, non-limiting
embodiment, the access point is a base station (BTS), enhanced with
the logic described herein, and the infrastructure need not include
a base station controller (BSC).
[0010] As set forth in greater detail below, the preferred
implementation distributes a selector functionality over the CAPs.
The functionality that is distributed over the CAPs can be thought
of as a selector entity that receives first communication device
frames from the first CAP when a first threshold is reached, and
monitors frame selection by the first CAP for the first
communication device. Moreover, a selector entity assumes frame
selection for the first communication device when a second
threshold is reached. At this point, the second CAP proposes frame
selections for the first communication device and forwards the
frame selections to the selector entity for monitoring thereby.
When the selector entity determines that frame selections from the
second CAP are within a predetermined correctness threshold, the
selector entity causes the second CAP to assume frame selection for
the first communication device.
[0011] In another aspect, a method for frame selection in a
wireless communication device infrastructure includes establishing
communication between at least a first base station (BTS) and at
least one wireless communication device using a non-Internet
protocol (IP) over-the-air (OTA) protocol. The first base station
is one of a plurality of base stations in an infrastructure. The
method includes selecting frames from the wireless communication
device at the first base station (BTS), and then selecting frames
from the wireless communication device at a second base station
(BTS).
[0012] In still another aspect, a computer program product includes
logic means for dynamically establishing a selector base station
(BTS) in a wireless telephony infrastructure that uses IP. Logic
means establish CDMA over-the-air communication between at least
one base station in the infrastructure and a CDMA wireless
communication device. Also, logic means hand off the selecting of
frames of information from the communication device from the
selector base station to a substitute base station upon reaching a
threshold.
[0013] In another aspect, a communication system includes at least
two wireless endpoints configured for CDMA communication with a
wireless communication device. The endpoints communicate with each
other using IP. At least a first one of the endpoints is
dynamically selected as a selector endpoint that undertakes a frame
selection service for the wireless communication device and that
undertakes handoff assistance for transferring frame selection from
the selector endpoint to a substitute endpoint in accordance with a
handoff algorithm.
[0014] In yet another aspect, a voice over Internet (VOIP) system
includes plural access points communicating with plural wireless
communication devices using a wireless communication device
over-the-air protocol that is different from Internet protocol
(IP). Each wireless communication device transmits frames of
information, and at least one access point undertakes frame
selection, including the addition and subtraction of access point
sectors to a call.
[0015] The details of the present invention, both as to its
structure and operation, can best be understood in reference to the
accompanying drawings, in which like reference numerals refer to
like parts, and in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a block diagram of one preferred implementation of
the wireless telephone system of the present invention;
[0017] FIG. 2 is a flow chart of the logic for frame selection at
one of the CDMA Access Points (CAP) of the present invention;
and
[0018] FIG. 3 is a flow chart of the logic for handing off frame
selection between CDMA access points (CAPs).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] Referring initially to FIG. 1, a system is shown, generally
designated 10, for effecting communication between a target
wireless communication device 12 such as but not limited to a
telephone that does not support Internet Protocol (IP) and a
telephony infrastructure 14 that does support IP. This invention is
directed to distributing the frame selection and handoff
functionality of a selector entity among plural base stations.
[0020] By "does not support VOIP" or "does not support IP" is meant
that the device 12 either has no IP or VOIP capability, or that it
has such capability but for improved performance uses a standard
over the air (OTA) protocol such as a spread spectrum scheme like
CDMA or WCDMA or other wireless protocol such as but not limited to
TDMA, UMTS, TD-SCDMA, etc. to communicate with the infrastructure
14. In one non-limiting embodiment the device 12 is a mobile
telephone made by Kyocera, Samsung, or other manufacturer that uses
Code Division Multiple Access (CDMA) principles and CDMA
over-the-air (OTA) communication air interface and includes
protocols such as defined in but not limited IS-95A, IS-95B, UCDMA,
IS-2000, and others to communicate with the infrastructure 14.
[0021] For instance, the wireless communication systems to which
the present invention can apply, in amplification to those noted
above, include Personal Communications Service (PCS) and cellular
systems, such as Analog Advanced Mobile Phone System (AMPS) and the
following digital systems: CDMA, Time Division Multiple Access
(TDMA), and hybrid systems that use both TDMA and CDMA
technologies. A CDMA cellular system is described in the
Telecommunications Industry Association/Electronic Industries
Association (TIA/EIA) Standard IS-95. Combined AMPS and CDMA
systems are described in TIA/EIA Standard IS-98. Other
communications systems are described in the International Mobile
Telecommunications System 2000/Universal Mobile Telecommunications
Systems (IMT-2000/UM), standards covering what are referred to as
wideband CDMA (WCDMA), cdma2000 (such as cdma2000 1.times. or
3.times. standards, for example) or TD-SCDMA.
[0022] The present invention applies to any wireless communication
device 12; for illustration it will be assumed that the device 12
is a telephone 12. In general, wireless communication devices to
which the present invention applies may include but are not limited
to a wireless handset or telephone, a cellular phone, a data
transceiver, or a paging and position determination receiver, and
can be hand-held, or portable as in vehicle-mounted (including
cars, trucks, boats, planes, trains), as desired. However, while
wireless communication devices are generally viewed as being
mobile, it is to be understood that the present invention can be
applied to "fixed" units in some implementations. Also, the present
invention applies to data modules or modems used to transfer voice
and/or data information including digitized video information, and
may communicate with other devices using wired or wireless links.
Further, commands might be used to cause modems or modules to work
in a predetermined coordinated or associated manner to transfer
information over multiple communication channels. Wireless
communication devices are also sometimes referred to as user
terminals, mobile stations, mobile units, subscriber units, mobile
radios or radiotelephones, wireless units, or simply as "users" and
"mobiles" in some communication systems.
[0023] As shown in FIG. 1, the wireless telephone 12 communicates
with at least one first infrastructure component 16. The first
component 16 is a code division multiple access (CDMA) access point
(CAP), and preferably is a base station (BTS). As intended herein,
the BTS does not communicate with a base station controller (BSC)
that is external to the BTS, i.e., the infrastructure 14 does not
contain a BSC. Less desirably, a BSC can be included in the
infrastructure, but with the below-disclosed frame selection
function being undertaken by a BTS.
[0024] A second CAP 18 is also established by a BTS of the
infrastructure 14. While for clarity of disclosure FIG. 1 shows
only two CAP 16, 18, it is to be understood that more than two CAPs
can be incorporated into the system 10. In any case, the functions
of frame selection and handoff control are distributed among the
CAP 16, 18.
[0025] In the presently preferred embodiment, communication within
the infrastructure 14 is via Internet Protocol (IP). The CAPs 16,
18 thus communicate with wireless telephones 12 using OTA protocol,
preferably using CDMA, but communicate internally to the
infrastructure 14 using IP, thereby relieving the wireless
telephone 12 from having to support IP. Also, by using IP
internally to the infrastructure 14 and OTA protocol to the
telephone 12, the advantages of using IP internal to the
infrastructure 14 are realized, whereas the advantages of OTA
protocol in wireless communication to the telephone 12 are
preserved to maximize the over-the-air capacity of the system 10.
Accordingly, the CAPs 16, 18 can be thought of as virtual IP
endpoints, with the actual communication endpoint being the
telephone 12.
[0026] FIG. 1 further shows that the target wireless telephone 12
can also communicate with communication devices outside the
infrastructure 14. Specifically, the infrastructure 14 can include
a VOIP gateway for communicating, in accordance with principles
known in the art, with a public switch telephone network (PSTN) 20.
The communication between the VOIP gateway and the PSTN 20 can be
via a signalling protocol such as ISUP using a physical system such
as SS7. In turn, the PSTN includes one or more landline devices
such as telephones or modems, to complete the communication pathway
between the target wireless telephone 12 and the landline
devices.
[0027] Additionally, the target wireless telephone 12 can
communicate with the Internet 22, including Internet-based
communication devices such as personal computers (PC) or other
computers, via the infrastructure 14. Still further, the
infrastructure 14 can communicate with wireless telephone systems
24 that are outside the infrastructure 14. Communication between
the infrastructure 14 and the other wireless/cellular systems 24
can be via IS-41 protocol or IP.
[0028] With the above overview of the present architecture in mind,
it is to be understood that the present logic is executed on the
architecture shown in FIG. 1 in accordance with the flow chart
discussed below. The flow charts herein illustrate the structure of
the logic of the present invention as embodied in computer program
software. Those skilled in the art will appreciate that the flow
charts illustrate the structures of logic elements, such as
computer program code elements or electronic logic circuits, that
function according to this invention. Manifestly, the invention is
practiced in its essential embodiment by a machine component that
renders the logic elements in a form that instructs a digital
processing apparatus (that is, a computer) to perform a sequence of
function steps corresponding to those shown.
[0029] In other words, the logic may be embodied by a computer
program that is executed by a processor within, e.g., the CAPs 16
and/or 18 as a series of computer-executable instructions. These
instructions may reside, for example, in RAM or on a hard drive or
optical drive, or the instructions may be stored on magnetic tape,
electronic read-only memory, or other appropriate data storage
device.
[0030] Now referring to FIG. 2, the logic of the present invention
in selecting frames is shown. Commencing at step 26, once
communication using an appropriate over-the-air (OTA) protocol is
established between the telephone 12 and the first CAP 16, i.e.,
between the telephone 12 and the virtual IP endpoint of the present
invention, the CAPs 16, 18 negotiate among themselves or otherwise
establish which CAP will initially function as the frame selector
CAP. That is, the CAPs can determine which one will have frame
selecting responsibility for the telephone 12 when the telephone 12
logs into the infrastructure 14. Frame selection also controls the
addition of base station/CAP sectors to a call as a mobile device
12 moves. Moreover, the frame selection CAP can assume the
below-described handoff function, or less preferably another CAP
can be assigned that function.
[0031] For instance, when the pilot signal is received from the
telephone 12 by only a single CAP, that CAP assumes frame selection
responsibility for the telephone, and informs the infrastructure 14
of this. On the other hand, when two or more CAPs initially detect
the telephone 12, the CAPs can use a negotiation protocol to
determine which CAP will undertake frame selection. In one
non-limiting embodiment used for illustration, the negotiation
protocol can include designating the CAP initially receiving the
strongest signal from the telephone 12 as the frame selector for
the telephone 12. Determining a frame selector CAP can thus be done
dynamically as the telephone 12 logs into the infrastructure
14.
[0032] In any case, when a wireless device 12 establishes
communication with a selector CAP, the selector CAP assigns the
device 12 a temporary IP address for all call setup functions
involving other communication endpoints. When an endpoint requests
a resource from an additional CAP or is handed off thereto, the
selector CAP associates a second IP address (such as an IP-port
number pair), and disseminates this second IP address to the
candidate CAP only. All IP packets from the endpoint arriving at
the candidate CAP are delivered to the second IP address, while all
call setup requests are delivered to the selector CAP. Additional
CAP can be treated similarly. The above-described multi-address
feature supports frame selection and handoff described below.
[0033] Proceeding to step 28, the selector CAP directs other CAPs
in the infrastructure 14 to forward all reverse-link frames (i.e.,
frames representing information transmitted by the telephone 12) to
the selector CAP. At step 29, the selector CAP undertakes frame
selection in accordance with frame selection principles known in
the art to select the "best" frame from the various CAPs to be the
frame for the call. Moreover, at step 30 the selector CAP sends
forward link frames (i.e., frames intended for the telephone 12) to
all CAPs (i.e., to all BTS) that are participating in the call, for
transmission thereof to the telephone 12.
[0034] In the preferred IP implementation of the infrastructure 14,
when communication is established, OTA packets such as OTA voice
packets from the wireless telephone 12 are transformed or otherwise
converted to IP at the virtual IP endpoints, i.e., at the CAPs 16,
18, etc. that are participating in the call. To make this
transformation, the contents of the OTA voice packets are
rearranged as appropriate to conform to IP packet requirements. The
information in IP is sent through the infrastructure 14 toward the
recipient.
[0035] Likewise, IP packets representing information intended for
the telephone 12 move through the infrastructure 14 and are
converted to OTA packets by the virtual IP endpoints (CAPs). The
OTA packets are sent to the telephone 12. The transformation from
IP to OTA protocol is the reverse of the process for converting OTA
packets to IP packets, i.e., each IP packet might be separated into
a set of smaller OTA packets as appropriate to conform to the OTA
protocol used by the telephone 12.
[0036] The present invention recognizes that it might be desirable
to hand off the frame selection process between CAPs as the
telephone moves between CAPs. The present invention further
recognizes that it would be desirable to reduce "dropped" calls as
frame selection is handed off between CAPs. With these critical
observations in mind, attention is now drawn to the logic flow
chart of FIG. 3.
[0037] Commencing at step 40, the first CAP 16 is initially
selected as a frame selector CAP for the wireless telephone 12. The
first CAP 16 can be the first BTS of the infrastructure 14 that
detects the wireless telephone 12. The first CAP 16 performs frame
selection in accordance with CDMA frame selection principles known
in the art.
[0038] Moving to decision diamond 42, it is determined whether a
first threshold is reached. In one non-limiting exemplary
embodiment, the first threshold can be a predetermined pilot
channel signal strength provided from the telephone 12 and
indicating a signal strength from the second CAP 18. Or, the first
threshold can be a predetermined pilot channel signal strength
provided from the second CAP 18 and indicating a signal strength
from the telephone 12. Or yet again, the first threshold can be
another type of signal strength or other network parameter.
[0039] When the first threshold is reached, the process proceeds to
step 44, wherein the first CAP 16 continues frame selection, and
also forwards both all frames received and "best" frame selections
to a selector entity, which can be a software or
hardware-implemented entity at the selector CAP or other CAP. That
is, the handoff functionality of a selector entity, formerly
centralized at a base station controller (BSC), is distributed
among the CAP in the present invention. Thus, the "selector entity"
referred to herein is implemented by one or more CAP, and indeed
the functionality of the selector entity can move from CAP to CAP
just as frame selection is distributed.
[0040] The selector entity can be incorporated anywhere in the
infrastructure 14, and can be implemented by hardware or software.
In any case, the selector entity, at step 46, informs the second
CAP 18 to send its frames from the telephone 12 to the selector
entity, instead of to the first CAP 16. The second CAP 18 makes
this change simply by changing the IP address of the frames to
match the IP address of the selector entity. The selector entity
can then relay the frames to the first CAP 16 to support continued
frame selection at the first CAP 16, while simultaneously
monitoring frame selection as reported back by the first CAP
16.
[0041] The process then monitors for the occurrence of a second
threshold. this step of the process is indicated at decision
diamond 48 in FIG. 3. The second threshold can be, e.g., a higher
predetermined pilot channel strength than the first threshold. When
the second threshold is reached, the selector entity assumes frame
selection and halts the frame selection process by the first CAP 16
at step 50. Moreover, the selector entity informs the second CAP 18
to propose "best" frame selections while continuing to forward
frames to the selector entity, and the selector entity monitors the
proposed frame selections from the second CAP 18.
[0042] When the propose frame selections are "correct" within a
predetermined correctness threshold, as indicated at decision
diamond 52, the selector entity causes the second CAP 18 to assume
frame selection at step 54. The selector entity then halts its own
frame selection and relieves the second CAP 18 from forwarding
frames to the selector entity. The above logic essentially effects
a "soft" handoff of the frame selection function from the first CAP
16 to the second CAP 18, thereby reducing the likelihood of dropped
calls as the telephone moves between the CAPs 16, 18.
[0043] While the particular SYSTEM AND METHOD FOR FRAME SELECTION
IN IP-BASED CDMA NETWORK as herein shown and described in detail is
fully capable of attaining the above-described objects of the
invention, it is to be understood that it is the presently
preferred embodiment of the present invention and is thus
representative of the subject matter which is broadly contemplated
by the present invention, that the scope of the present invention
fully encompasses other embodiments which may become obvious to
those skilled in the art, and that the scope of the present
invention is accordingly to be limited by nothing other than the
appended claims, in which reference to an element in the singular
is not intended to mean "one and only one" unless explicitly so
stated, but rather "one or more". All structural and functional
equivalents to the elements of the above-described preferred
embodiment that are known or later come to be known to those of
ordinary skill in the art are expressly incorporated herein by
reference and are intended to be encompassed by the present claims.
Moreover, it is not necessary for a device or method to address
each and every problem sought to be solved by the present
invention, for it to be encompassed by the present claims.
[0044] Furthermore, no element, component, or method step in the
present disclosure is intended to be dedicated to the public
regardless of whether the element, component, or method step is
explicitly recited in the claims. No claim element herein is to be
construed under the provisions of 35 U.S.C. .sctn. 112, sixth
paragraph, unless the element is expressly recited using the phrase
"means for" or, in the case of a method claim, the element is
recited as a "step" instead of an "act".
* * * * *