U.S. patent application number 14/454588 was filed with the patent office on 2018-04-12 for reducing frequent handoffs of a wireless communication device.
The applicant listed for this patent is QUALCOMM INCORPORATED. Invention is credited to Sanjiv Nanda, Chirag Sureshbhai Patel, Mehmet Yavuz.
Application Number | 20180103446 14/454588 |
Document ID | / |
Family ID | 43220799 |
Filed Date | 2018-04-12 |
United States Patent
Application |
20180103446 |
Kind Code |
A9 |
Patel; Chirag Sureshbhai ;
et al. |
April 12, 2018 |
REDUCING FREQUENT HANDOFFS OF A WIRELESS COMMUNICATION DEVICE
Abstract
A method for reducing frequent idle handoffs of a wireless
communication device is described. A registration request is
received by a base station or a femto access point from the
wireless communication device. The number of registration requests
received from the wireless communication device are counted while
the registration timer is running. It is determined that frequent
handoffs are happening when the number of registration requests
received is greater than a registration threshold. A transmit power
of a femto access point is adjusted if the number of registration
requests received indicates that frequent handoffs are
happening.
Inventors: |
Patel; Chirag Sureshbhai;
(San Diego, CA) ; Yavuz; Mehmet; (San Diego,
CA) ; Nanda; Sanjiv; (Ramona, CA) |
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Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM INCORPORATED |
San Diego |
CA |
US |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20160044624 A1 |
February 11, 2016 |
|
|
Family ID: |
43220799 |
Appl. No.: |
14/454588 |
Filed: |
August 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12789213 |
May 27, 2010 |
8843131 |
|
|
14454588 |
|
|
|
|
61181882 |
May 28, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 52/143 20130101;
H04W 36/00 20130101; H04W 60/00 20130101; H04W 16/32 20130101; H04W
4/06 20130101; H04W 76/28 20180201; Y02D 30/70 20200801; Y02D
70/1242 20180101; H04W 52/325 20130101; H04W 84/045 20130101; H04W
88/02 20130101; H04W 48/20 20130101; H04W 52/40 20130101; Y02D
70/1262 20180101; H04W 52/0212 20130101; H04W 60/04 20130101; H04W
36/0083 20130101; Y02D 70/146 20180101; Y02D 70/142 20180101 |
International
Class: |
H04W 60/04 20060101
H04W060/04; H04W 36/00 20060101 H04W036/00; H04W 4/06 20060101
H04W004/06; H04W 52/02 20060101 H04W052/02 |
Claims
1. A method for reducing frequent idle handoffs of a wireless
communication device, comprising: sending a registration request to
a femto access point; detecting a trigger for an idle handoff away
from the femto access point; starting a handout timer; and
determining whether a handout trigger condition is satisfied within
a monitoring period after the handout timer has expired.
2. The method of claim 1, wherein the trigger for an idle handoff
away from the femto access point is an idle handout trigger.
3. The method of claim 1, further comprising performing an idle
handoff away from the femto access point if the handout trigger
condition is satisfied within a monitoring period after the handout
timer has expired.
4. The method of claim 1, further comprising staying on the femto
access point if the handout trigger condition is not satisfied
within a monitoring period after the handout timer has expired.
5. The method of claim 1, further comprising comparing a forward
link received power from the femto access point with a handout
threshold before the handout timer has expired, wherein the idle
handoff away from the femto access point is performed prior to the
handout timer expiring if the forward link received power from the
femto access point is less than the handout threshold.
6. The method of claim 1, further comprising: starting an
observation timer; counting a number of registrations attempted to
the femto access point before the observation timer has expired;
and performing an idle handoff away from the femto access point
after the observation timer has expired if the number of
registrations attempted to the femto access point is greater than
an observation threshold and handoff away from the femto access
point is triggered.
7. The method of claim 1, wherein the wireless communication device
is part of a closed subscriber group (CSG) associated with the
femto access point.
8. The method of claim 1, wherein the wireless communication device
is not part of a closed subscriber group (CSG) associated with the
femto access point.
9. The method of claim 1, wherein the trigger for an idle handoff
away from the femto access point is to a macro base station.
10. The method of claim 1, wherein the wireless communication
device is able to distinguish between pilots received from the
femto access point and pilots received from a macro base
station.
11. A wireless device configured for reducing frequent idle
handoffs of the wireless device, comprising: a processor; memory in
electronic communication with the processor; instructions stored in
the memory, the instructions being executable by the processor to:
send a registration request to a femto access point; detect a
trigger for an idle handoff away from the femto access point; start
a handout timer; and determine whether a handout trigger condition
is satisfied within a monitoring period after the handout timer has
expired.
12. The wireless device of claim 11, wherein the trigger for an
idle handoff away from the femto access point is an idle handout
trigger.
13. The wireless device of claim 11, wherein the instructions are
further executable by the processor to perform an idle handoff away
from the femto access point if the handout trigger condition is
satisfied within a monitoring period after the handout timer has
expired.
14. The wireless device of claim 11, wherein the instructions are
further executable by the processor to stay on the femto access
point if the handout trigger condition is not satisfied within a
monitoring period after the handout timer has expired.
15. The wireless device of claim 11, wherein the instructions are
further executable to compare a forward link received power from
the femto access point with a handout threshold before the handout
timer has expired, wherein the idle handoff away from the femto
access point is performed prior to the handout timer expiring if
the forward link received power from the femto access point is less
than the handout threshold.
16. The wireless device of claim 11, wherein the instructions are
further executable to: start an observation timer; count a number
of registrations attempted to the femto access point before the
observation timer has expired; and perform an idle handoff away
from the femto access point after the observation timer has expired
if the number of registrations attempted to the femto access point
is greater than an observation threshold and handoff away from the
femto access point is triggered.
17. The wireless device of claim 11, wherein the wireless
communication device is part of a closed subscriber group (CSG)
associated with the femto access point.
18. The wireless device of claim 11, wherein the wireless
communication device is not part of a closed subscriber group (CSG)
associated with the femto access point.
19. The wireless device of claim 11, wherein the trigger for an
idle handoff away from the femto access point is to a macro base
station.
20. The wireless device of claim 11, wherein the wireless
communication device is able to distinguish between pilots received
from the femto access point and pilots received from a macro base
station.
21. A wireless device configured for reducing frequent idle
handoffs of the wireless device, comprising: means for sending a
registration request to a femto access point; means for detecting a
trigger for an idle handoff away from the femto access point; means
for starting a handout timer; and means for determining whether a
handout trigger condition is satisfied within a monitoring period
after the handout timer has expired.
22. The wireless device of claim 21, further comprising means for
performing an idle handoff away from the femto access point if the
handout trigger condition is satisfied within a monitoring period
after the handout timer has expired.
23. The wireless device of claim 21, further comprising means for
staying on the femto access point if the handout trigger condition
is not satisfied within a monitoring period after the handout timer
has expired.
24. The wireless device of claim 21, further comprising means for
comparing a forward link received power from the femto access point
with a handout threshold before the handout timer has expired,
wherein the idle handoff away from the femto access point is
performed prior to the handout timer expiring if the forward link
received power from the femto access point is less than the handout
threshold.
25. The wireless device of claim 21, further comprising: means for
starting an observation timer; means for counting a number of
registration attempts to the femto access point before the
observation timer has expired; and means for performing the idle
handoff away from the femto access point before the observation
timer has expired if the number of registration attempts to the
femto access point is greater than an observation threshold and
handoff away from the femto access point is triggered.
26. A computer-program product for reducing frequent idle handoffs
of a wireless communication device, the computer-program product
comprising a computer-readable medium having instructions thereon,
the instructions comprising: code for causing at least one computer
to send a registration request to a femto access point; code for
causing at least one computer to detect a trigger for an idle
handoff away from the femto access point; code for causing at least
one computer to start a handout timer; and code for determining
whether a handout trigger condition is satisfied within a
monitoring period after the handout timer has expired.
27. The computer-program product of claim 26, wherein the
instructions further comprise code for causing at least one
computer to perform an idle handoff away from the femto access
point if the handout trigger condition is satisfied within a
monitoring period after the handout timer has expired.
28. The computer-program product of claim 26, wherein the
instructions further comprise code for causing at least one
computer to stay on the femto access point if the handout trigger
condition is not satisfied within a monitoring period after the
handout timer has expired.
29. The computer-program product of claim 26, wherein the
instructions further comprise code for causing at least one
computer to compare a forward link received power from the femto
access point with a handout threshold before the handout timer has
expired, wherein the idle handoff away from the femto access point
is performed prior to the handout timer expiring if the forward
link received power from the femto access point is less than the
handout threshold.
30. The computer-program product of claim 26, wherein the
instructions further comprise: code for causing at least one
computer to start an observation timer; code for causing at least
one computer to count a number of registration attempts to the
femto access point before the observation timer has expired; and
code for causing at least one computer to perform the idle handoff
away from the femto access point after the observation timer has
expired if the number of registration attempts to the femto access
point is greater than an observation threshold and idle handoff
away from the femto access point is triggered.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of, and claims priority to,
U.S. patent application Ser. No. 12/789,213, filed May 27, 2010,
for "Reducing Frequent Handoffs of a Wireless Communication
Device," which claims the benefit of priority to U.S. Provisional
Patent Application Ser. No. 61/181,882, filed May 28, 2009, for
"Optimization of Idle Mode Search and Handoffs in Femto-Macro
Deployments," of which are hereby incorporated by reference in
their entirety.
TECHNICAL FIELD
[0002] The present disclosure relates generally to wireless
communication systems. More specifically, the present disclosure
relates to systems and methods for reducing frequent handoffs of a
wireless communication device to/from a femto access point.
BACKGROUND
[0003] Wireless communication systems have become an important
means by which many people worldwide have come to communicate. A
wireless communication system may provide communication for a
number of mobile stations, each of which may be serviced by a base
station.
[0004] It may be beneficial to use localized base stations that
provide service to a select group of mobile stations. These
localized base stations may use less power and have smaller
coverage areas than normal base stations. The localized base
stations may then provide a mobile station with active voice/data
access. As localized base stations continue to improve, more
localized base stations will become prevalent.
[0005] Examples of localized base stations include femtocells and
picocells. Localized base stations may be referred to as femto
access points without loss of generality. These localized base
stations may be controlled by a user. For example, a localized base
station may be purchased by an end user and placed in their home or
office to increase wireless coverage. A localized base station may
also be controlled by a service provider. For example, a service
provider may place a localized base station in a public area with
high traffic.
[0006] As a mobile station approaches a localized base station, the
mobile station may detect the localized base station and attempt to
access it by sending a registration request. The localized base
station may then determine whether to allow access to this mobile
station for different services such as a voice/data connection with
the mobile station. Registration requests reduce the battery life
of the mobile station and increase the network load. As such,
benefits may be realized by reducing the number of registration
requests made by a mobile station.
SUMMARY
[0007] A method for reducing frequent idle handoffs of a wireless
communication device is described. A registration request is
received from the wireless communication device. A registration
timer is started. A number of registration requests received from
the wireless communication device is counted while the registration
timer is running It is determined whether the number of
registration requests received is greater than a registration
threshold. A transmit power of a femto access point is adjusted if
the number of registration requests received is greater than the
registration threshold.
[0008] The wireless communication device may be part of a closed
subscriber group (CSG) associated with the femto access point.
Adjusting the transmit power of the femto access point may include
increasing the transmit power of the femto access point. The
wireless communication device may not be part of a closed
subscriber group (CSG) associated with the femto access point.
Adjusting the transmit power of the femto access point may include
decreasing the transmit power of the femto access point. The
transmit power of the femto access point may be adjusted by a power
adjustment factor.
[0009] A power adjustment timer with a power adjustment time may be
started. It may be determined whether the power adjustment timer
has expired. It also may be determined whether frequent idle
handoffs by the wireless communication device were detected while
the power adjustment timer was running Frequent handoffs by the
wireless communication device may be detected while the power
adjustment timer was running. The power adjustment time may be
incrementally increased. The power adjustment factor may also be
incrementally increased.
[0010] Frequent handoffs by the wireless communication device may
not be detected while the power adjustment timer was running. The
power adjustment time may be incrementally decreased. The power
adjustment factor may also be incrementally decreased. The transmit
power may be readjusted to a previous transmit power. Adjusting the
transmit power of the femto access point may include adjusting a
total forward link transmit power of the femto access point or
adjusting a forward link pilot transmit power of the femto access
point. A registration request may be an active handoff request
passed via a core network.
[0011] A wireless device configured for reducing frequent idle
handoffs of a wireless communication device is also described. The
wireless device includes a processor, memory in electronic
communication with the processor and instructions stored in the
memory. The instructions are executable by the processor to receive
a registration request from the wireless communication device. The
instructions are also executable by the processor to start a
registration timer. The instructions are further executable by the
processor to count a number of registration requests received from
the wireless communication device while the registration timer is
running. The instructions are also executable by the processor to
determine whether the number of registration requests received is
greater than a registration threshold. The instructions are further
executable by the processor to adjust a transmit power of the
wireless device if the number of registration requests received is
greater than the registration threshold.
[0012] A method for reducing frequent idle handoffs of a wireless
communication device is described. A registration request is sent
to a femto access point. A trigger for an idle handoff away from
the femto access point is detected. A handout timer is started. It
is determined whether a handout trigger condition is satisfied
within a monitoring period after the handout timer has expired.
[0013] The trigger for an idle handoff away from the femto access
point may be an idle handout trigger. An idle handoff away from the
femto access point may be performed if the handout trigger
condition is satisfied within a monitoring period after the handout
timer has expired. The method may include staying on the femto
access point if the handout trigger condition is not satisfied
within a monitoring period after the handout timer has expired.
[0014] A forward link received power from the femto access point
may be compared with a handout threshold before the handout timer
has expired. The idle handoff away from the femto access point may
be performed prior to the handout timer expiring if the forward
link received power from the femto access point is less than the
handout threshold.
[0015] An observation timer may be started. A number of
registrations attempted to the femto access point before the
observation timer has expired may be counted. An idle handoff away
from the femto access point may be performed after the observation
timer has expired if the number of registrations attempted to the
femto access point is greater than an observation threshold and
handoff away from the femto access point is triggered.
[0016] The wireless communication device may be part of a closed
subscriber group (CSG) associated with the femto access point. The
wireless communication device may also not be part of a closed
subscriber group (CSG) associated with the femto access point. The
trigger for an idle handoff away from the femto access point may be
to a macro base station. The wireless communication device may be
able to distinguish between pilots received from the femto access
point and pilots received from a macro base station.
[0017] A wireless device configured for reducing frequent idle
handoffs of the wireless device is also described. The wireless
device includes a processor, memory in electronic communication
with the processor and instructions stored in the memory. The
instructions are executable by the processor to send a registration
request to a femto access point. The instructions are also
executable by the processor to detect a trigger for an idle handoff
away from the femto access point. The instructions are further
executable by the processor to start a handout timer. The
instructions are also executable by the processor to determine
whether a handout trigger condition is satisfied within a
monitoring period after the handout timer has expired.
[0018] A method for reducing frequent idle handoffs of a wireless
communication device is described. The method includes determining
that changes to an idle mode pilot search trigger threshold are
needed. The idle mode pilot search trigger threshold is
adjusted.
[0019] The method may be performed by a femto access point.
Adjusting the idle mode pilot search trigger threshold may include
sending instructions to the wireless communication device to adjust
the idle mode pilot search trigger threshold.
[0020] The method may be performed by the wireless communication
device. Determining that changes to an idle mode pilot search
trigger threshold are needed may include receiving instructions to
adjust the idle mode pilot search trigger threshold from a femto
access point.
[0021] A wireless device configured for reducing frequent idle
handoffs of a wireless communication device is also described. The
wireless device includes a processor, memory in electronic
communication with the processor and instructions stored in the
memory. The instructions are executable by the processor to
determine that changes to an idle mode pilot search trigger
threshold are needed. The instructions are also executable by the
processor to adjust the idle mode pilot search trigger
threshold.
[0022] A wireless device configured for reducing frequent idle
handoffs of a wireless communication device is described. The
wireless device includes means for receiving a registration request
from the wireless communication device. The wireless device also
includes means for starting a registration timer. The wireless
device further includes means for counting a number of registration
requests received from the wireless communication device while the
registration timer is running The wireless device also includes
means for determining whether the number of registration requests
received is greater than a registration threshold. The wireless
device further includes means for adjusting a transmit power of the
femto access point if the number of registration requests received
is greater than the registration threshold.
[0023] A computer-program product for reducing frequent idle
handoffs of a wireless communication device is described. The
computer-program product includes a computer-readable medium having
instructions thereon. The instructions include code for causing at
least one computer to receive a registration request from the
wireless communication device. The instructions also include code
for causing at least one computer to start a registration timer.
The instructions further include code for causing at least one
computer to count a number of registration requests received from
the wireless communication device while the registration timer is
running The instructions also include code for causing at least one
computer to determine whether the number of registration requests
received is greater than a registration threshold. The instructions
further include code for causing at least one computer to adjust a
transmit power of the femto access point if the number of
registration requests received is greater than the registration
threshold.
[0024] A wireless device configured for reducing frequent idle
handoffs of the wireless device is also described. The wireless
device includes means for sending a registration request to a femto
access point. The wireless device also includes means for detecting
a trigger for an idle handoff away from the femto access point. The
wireless device further includes means for starting a handout
timer. The wireless device also includes means for determining
whether a handout trigger condition is satisfied within a
monitoring period after the handout timer has expired.
[0025] A computer-program product for reducing frequent idle
handoffs of a wireless communication device is described. The
computer-program product is a computer-readable medium having
instructions thereon. The instructions include code for causing at
least one computer to send a registration request to a femto access
point. The instructions also include code for causing at least one
computer to detect a trigger for an idle handoff away from the
femto access point. The instructions further include code for
causing at least one computer to start a handout timer. The
instructions also include code for determining whether a handout
trigger condition is satisfied within a monitoring period after the
handout timer has expired.
[0026] A wireless device configured for reducing frequent idle
handoffs of a wireless communication device is described. The
wireless device includes means for determining that changes to an
idle mode pilot search trigger threshold are needed. The wireless
device also includes means for adjusting the idle mode pilot search
trigger threshold.
[0027] A computer-program product for reducing frequent idle
handoffs of a wireless communication device is described. The
computer-program product is a computer-readable medium having
instructions thereon. The instructions include code for causing at
least one computer to determine that changes to an idle mode pilot
search trigger threshold are needed. The instructions also include
code for causing at least one computer to adjust the idle mode
pilot search trigger threshold.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 illustrates a wireless communication system,
configured to support a number of users, in which the teachings
herein may be implemented;
[0029] FIG. 2 illustrates an exemplary communication system where
one or more femto nodes are deployed within a network
environment;
[0030] FIG. 3 illustrates an example of a coverage map where
several tracking areas (or routing areas or location areas) are
defined, each of which includes several macro coverage areas;
[0031] FIG. 4 shows a wireless communication system with multiple
wireless devices;
[0032] FIG. 5 is a block diagram of a frequent handoff reduction
module;
[0033] FIG. 6 is a flow diagram of a method for reducing frequent
handoffs;
[0034] FIG. 7 illustrates means-plus-function blocks corresponding
to the method of FIG. 6;
[0035] FIG. 8 is another flow diagram of a method for reducing
frequent handoffs;
[0036] FIG. 9 illustrates means-plus-function blocks corresponding
to the method of FIG. 8;
[0037] FIG. 10 is a flow diagram of yet another method for reducing
frequent handoffs;
[0038] FIG. 11 illustrates means-plus-function blocks corresponding
to the method of FIG. 10;
[0039] FIG. 12 is a block diagram illustrating a handoff
determination module;
[0040] FIG. 13 is a flow diagram of a method for reducing handoffs
by a wireless communication device;
[0041] FIG. 14 illustrates means-plus-function blocks corresponding
to the method of FIG. 13;
[0042] FIG. 15 is a flow diagram of another method for reducing
frequent handoffs by a wireless communication device;
[0043] FIG. 16 illustrates means-plus-function blocks corresponding
to the method of FIG. 15;
[0044] FIG. 17 illustrates two wireless devices in a multiple-in
and multiple-out (MIMO) system;
[0045] FIG. 18 illustrates certain components that may be included
within a femto access point; and
[0046] FIG. 19 illustrates certain components that may be included
within a wireless communication device.
DETAILED DESCRIPTION
[0047] FIG. 1 illustrates a wireless communication system 100,
configured to support a number of users, in which the teachings
herein may be implemented. The system 100 provides communication
for multiple cells 102, such as, for example, macro cells
102A-102G, with each cell being serviced by a corresponding access
node 104 (e.g., access nodes 104A-104G). As shown in FIG. 1, access
terminals 106 (e.g., access terminals 106A-106L) may be dispersed
at various locations throughout the system over time. Each access
terminal 106 may communicate with one or more access nodes 104 on a
forward link ("FL") and/or a reverse link ("RL") at a given moment,
depending upon whether the access terminal 106 is active and
whether it is in soft handoff, for example. The wireless
communication system 100 may provide service over a large
geographic region. For example, macro cells 102A-102G may cover a
few blocks in a neighborhood.
[0048] In some aspects, the teachings herein may be employed in a
network that includes macro scale coverage (e.g., a large area
cellular network such as a 3G networks, typically referred to as a
macro cell network) and smaller scale coverage (e.g., a
residence-based or building-based network environment). As an
access terminal ("AT") moves through such a network, the access
terminal may be served in certain locations by access nodes ("ANs")
that provide macro coverage while the access terminal may be served
at other locations by access nodes that provide smaller scale
coverage. In some aspects, the smaller coverage nodes may be used
to provide incremental capacity growth, in-building coverage and
different services (e.g., for a more robust user experience). In
the discussion herein, a node that provides coverage over a
relatively large area may be referred to as a macro node. A node
that provides coverage over a relatively small area (e.g., a
residence) may be referred to as a femto node. A node that provides
coverage over an area that is smaller than a macro area and larger
than a femto area may be referred to as a pico node (e.g.,
providing coverage within a commercial building).
[0049] A cell associated with a macro node, a femto node or a pico
node may be referred to as a macro cell, a femto cell, or a pico
cell, respectively. In some implementations, each cell may be
further associated with (e.g., divided into) one or more
sectors.
[0050] In various applications, other terminology may be used to
reference a macro node, a femto node, or a pico node. For example,
a macro node may be configured or referred to as an access node,
base station, macro base station, access point, evolved NodeB
(eNB), macro cell and so on. Also, a femto node may be configured
or referred to as a Home NodeB (HNB), Home evolved NodeB (HeNB),
access point base station, femto cell, femto access point and so
on.
[0051] FIG. 2 illustrates an exemplary communication system 200
where one or more femto nodes, also known as femto access points,
are deployed within a network environment. The system 200 includes
multiple femto nodes 211 (e.g., femto nodes 211A and 211B)
installed in a relatively small scale network environment (e.g., in
one or more user residences 208). Each femto node 211 may be
coupled to a wide area network 214 (e.g., the Internet) and a
mobile operator core network 212 via a DSL router, a cable modem, a
wireless link or other connectivity means (not shown). As will be
discussed below, each femto node 211 may be configured to serve
associated access terminals 206, also known as user equipment,
(e.g., access terminal 206A) and, optionally, alien access
terminals 206 (e.g., access terminal 206B). In other words, access
to femto nodes 211 may be restricted whereby a given femto node 211
may serve a set of designated access terminals 206 (e.g., home
access terminals 206) but may serve any non-designated access
terminals 206 (e.g., access terminals 206 of a neighbor).
[0052] The owner of a femto node 211 may subscribe to mobile
service, such as, for example, 3G mobile service, offered through
the mobile operator core network 212. In addition, an access
terminal 206 may be capable of operating both in macro environments
and in smaller scale (e.g., residential) network environments. In
other words, depending on the current location of the access
terminal 206, the access terminal 206 may be served by an access
node 210 of the macro cell mobile network or by any one of a set of
femto nodes 211 (e.g., the femto nodes 211A and 211B that reside
within a corresponding user residence 208). For example, when a
subscriber is outside his home, he is served by a standard macro
access node (e.g., node 210) and when the subscriber is at home, he
is served by a femto node (e.g., node 211A). Here, it should be
appreciated that a femto node 211 may be backward compatible with
existing access terminals 206.
[0053] A femto node 211 may be deployed on a single frequency or,
in the alternative, on multiple frequencies. Depending on the
particular configuration, the single frequency or one or more of
the multiple frequencies may overlap with one or more frequencies
used by a macro node (e.g., node 210).
[0054] In some aspects, an access terminal 206 may be configured to
connect to a preferred femto node (e.g., the home femto node of the
access terminal 206) whenever such connectivity is possible. For
example, whenever the access terminal 206 is within the user's
residence 208, it may be desired that the access terminal 206
communicate only with the home femto node 211.
[0055] In some aspects, if the access terminal 206 operates within
the macro cellular network 210 but is not residing on its most
preferred network (e.g., as defined in a preferred roaming list),
the access terminal 206 may continue to search for the most
preferred network (e.g., the preferred femto node 211) using a
Better System Reselection ("BSR"), which may involve a periodic
scanning of available systems to determine whether better systems
are currently available, and subsequent efforts to associate with
such preferred systems. The access terminal 206 may limit the
search for specific band and channel. For example, the search for
the most preferred system may be repeated periodically. Upon
discovery of a preferred femto node 211, the access terminal 206
selects the femto node 211 for camping within its coverage
area.
[0056] A femto node may be restricted in some aspects. For example,
a given femto node may only provide certain services to certain
access terminals. In deployments with so-called restricted (or
closed) association, a given access terminal may only be served by
the macro cell mobile network and a defined set of femto nodes
(e.g., the femto nodes 211 that reside within the corresponding
user residence 208). In some implementations, a node may be
restricted to not provide signaling, data access, registration,
paging or service.
[0057] In some aspects, a restricted femto node (which may also be
referred to as a Closed Subscriber Group Home NodeB) is one that
provides service to a restricted provisioned set of access
terminals. This set may be temporarily or permanently extended as
necessary. In some aspects, a Closed Subscriber Group ("CSG") may
be defined as the set of access terminals/subscribers to which
access to the restricted femto node is allowed. A channel on which
all femto nodes (or all restricted femto nodes) in a region operate
may be referred to as a femto channel.
[0058] Various relationships may thus exist between a given femto
node and a given access terminal. For example, from the perspective
of an access terminal, an open femto node may refer to a femto node
with no restricted association. A restricted femto node may refer
to a femto node that is restricted in some manner (e.g., restricted
for association and/or registration). A home femto node may refer
to a femto node on which the access terminal is authorized to
access and operate on. A guest femto node may refer to a femto node
on which an access terminal is temporarily authorized to access or
operate on. An alien femto node may refer to a femto node on which
the access terminal is not authorized to access or operate on,
except for perhaps emergency situations (e.g., 911 calls).
[0059] From a restricted femto node perspective, a home access
terminal may refer to an access terminal that is authorized to
access the restricted femto node. A guest access terminal may refer
to an access terminal with temporary access to the restricted femto
node. An alien access terminal may refer to an access terminal that
does not have permission to access the restricted femto node,
except for perhaps emergency situations, for example, such as 911
calls (e.g., an access terminal that does not have the credentials
or permission to register with the restricted femto node).
[0060] For convenience, the disclosure herein describes various
functionality in the context of a femto node. It should be
appreciated, however, that a pico node may provide the same or
similar functionality for a larger coverage area. For example, a
pico node may be restricted, a home pico node may be defined for a
given access terminal, and so on.
[0061] FIG. 3 illustrates an example of a coverage map 300 where
several tracking areas 315 (or routing areas or location areas) are
defined, each of which includes several macro coverage areas 316.
Here, areas of coverage associated with tracking areas 315A, 315B
and 315C are delineated by the wide lines and the macro coverage
areas 316A and 316B are represented by the hexagons. The tracking
areas 315 also include femto coverage areas 317A, 317B and 317C. In
this example, each of the femto coverage areas 317 (e.g., femto
coverage area 317C) is depicted within a macro coverage area 316
(e.g., macro coverage area 316B). It should be appreciated,
however, that a femto coverage area 317 may not lie entirely within
a macro coverage area 316. In practice, a large number of femto
coverage areas 317 may be defined with a given tracking area 315 or
macro coverage area 316. Also, one or more pico coverage areas (not
shown) may be defined within a given tracking area 315 or macro
coverage area 316.
[0062] FIG. 4 shows a wireless communication system 400 with
multiple wireless devices. Wireless communication systems 400 are
widely deployed to provide various types of communication content
such as voice, data, and so on. These systems may be
multiple-access systems capable of supporting communication with
multiple users by sharing the available system resources (e.g.,
bandwidth and transmit power). A wireless device may be a base
station or a wireless communication device.
[0063] A base station is a station that communicates with one or
more wireless communication devices. A base station may also be
referred to as, and may include some or all of the functionality
of, an access point, a broadcast transmitter, a NodeB, an evolved
NodeB, etc. The term "base station" will be used herein. Each base
station provides communication coverage for a particular geographic
area. A base station may provide communication coverage for one or
more wireless communication devices. The term "cell" can refer to a
base station and/or its coverage area depending on the context in
which the term is used.
[0064] A mobile station or device may be referred to as a wireless
communication device. A base station may be referred to as an
evolved NodeB (eNB). A semi-autonomous base station may be referred
to as a home evolved NodeB (HeNB). An HeNB may thus be one example
of an eNB. The HeNB and/or the coverage area of an HeNB may be
referred to as a femtocell, a picocell, a home NodeB (HNB) cell, an
HeNB cell, a femto access point, a femto node or a closed
subscriber group (CSG) cell. Femto access point terminology is used
hereinafter. Femto access points are low power base stations that
extend the range of conventional wide area network base stations.
Femto access points provide voice and high speed data service
inside homes and offices for wireless communication devices
supporting cellular radio communication techniques. Access to a
femto access point depends on the kind of access control that the
femto access point uses. With open access, any wireless
communication device can access and receive service from a femto
access point. With closed subscriber group (CSG) or restricted
access, only members of the closed subscriber group (CSG) are
allowed to access and receive service from a femto access point
419.
[0065] Communications in a wireless system (e.g., a multiple-access
system) may be achieved through transmissions over a wireless link.
Such a communication link may be established via a single-input and
single-output (SISO), multiple-input and single-output (MISO), or a
multiple-input and multiple-output (MIMO) system. A MIMO system
includes transmitter(s) and receiver(s) equipped, respectively,
with multiple (NT) transmit antennas and multiple (NR) receive
antennas for data transmission. SISO and MISO systems are
particular instances of a MIMO system. The MIMO system can provide
improved performance (e.g., higher throughput, greater capacity or
improved reliability) if the additional dimensionalities created by
the multiple transmit and receive antennas are utilized.
[0066] A MIMO system may support time division duplex (TDD) and
frequency division duplex (FDD). In a TDD system, the uplink and
downlink transmissions are on the same frequency region so that the
reciprocity principle allows the estimation of the uplink channel
from the downlink channel.
[0067] The teachings herein may be incorporated into various types
of communication systems and/or system components. In some aspects,
the teachings herein may be employed in a multiple-access system
capable of supporting communication with multiple users by sharing
the available system resources (e.g., by specifying one or more of
bandwidth, transmit power, coding, interleaving, and so on). For
example, the teachings herein may be applied to any one or
combinations of the following technologies: Code Division Multiple
Access (CDMA) systems, Multiple-Carrier CDMA (MCCDMA), Wideband
CDMA (W-CDMA), High-Speed Packet Access (HSPA, HSPA+) systems, Time
Division Multiple Access (TDMA) systems, Frequency Division
Multiple Access (FDMA) systems, Single-Carrier FDMA (SC-FDMA)
systems, Orthogonal Frequency Division Multiple Access (OFDMA)
systems or other multiple access techniques.
[0068] A wireless communication system employing the teachings
herein may be designed to implement one or more standards, such as
IS-95, cdma2000, IS-856, W-CDMA, time division synchronous code
division multiple access (TD-SCDMA) and other standards. A CDMA
network may implement a radio technology such as Universal
Terrestrial Radio Access (UTRA), cdma2000 or some other technology.
UTRA includes W-CDMA and Low Chip Rate (LCR). The cdma2000
technology covers IS-2000, IS-95 and IS-856 standards. A TDMA
network may implement a radio technology such as Global System for
Mobile Communications (GSM). An OFDMA network may implement a radio
technology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16,
IEEE 802.20, Flash-OFDM.RTM., etc. UTRA, E-UTRA and GSM are part of
Universal Mobile Telecommunication System (UMTS). The teachings
herein may be implemented in a Third Generation Partnership Project
(3GPP) Long Term Evolution (LTE) system, an Ultra-Mobile Broadband
(UMB) system and other types of systems. LTE is a release of UMTS
that uses E-UTRA. Although certain aspects of the disclosure may be
described using 3GPP terminology, it is to be understood that the
teachings herein may be applied to 3GPP (Rel99, Rel5, Rel6, Rel7)
technology, as well as 3GPP2 (IxRTT, 1xEV-DO RelO, RevA, RevB)
technology and other technologies. For clarity, certain aspects of
the techniques are described below for cdma2000, and cdma2000
terminology is used in much of the description below.
[0069] Low power base stations such as home NodeBs (HNBs), home
evolved NodeBs (HeNB), picocells and femtocells are used in
addition to the normal base stations (a normal base station is
referred to herein as a macro base station 418). A picocell may
refer to a base station controlled by the network operator that
operates on a much smaller scale than a macro base station. A
femtocell may refer to a base station controlled by a consumer that
operates on a much smaller scale than a macro base station. A
femtocell may provide service to a closed subscriber group (CSG).
HNBs, HeNBs, picocells and femtocells are referred to herein as
femto access points 419.
[0070] A femto access point 419 may provide benefits to a
subscriber in the form of improved coverage inside the house/office
and the possibility of special pricing plans. For example, an
operator may provide unlimited voice/data usage when the user is
using a femto access point 419 for a nominal charge. The operator
may benefit from additional system capacity made available by
offloading some of the traffic to femto access points 419.
[0071] From both a user and an operator perspective, it is
desirable to maximize usage of a femto access point. When a user
comes home, a wireless communication device 420 should perform idle
handoff from a macro base station 418 to the femto access point 419
so that the user can initiate/receive calls using the femto access
point 419. While moving around the home, the wireless communication
device 420 may stay in idle mode (camp) on the femto access point
419 as long as the coverage of the femto access point 419 is
adequate. A good mechanism is needed to control idle handoff by a
wireless communication device 420, make a wireless communication
device 420 stay connected to a femto access point 419 in idle mode
and/or active mode longer (i.e. "stick to the femto access point
419") and prevent frequent idle handoffs between a femto access
point 419 and a macro base station 418 in cdma2000 systems.
[0072] A base station may communicate with one or more wireless
communication devices 420a-b. A wireless communication device 420
may also be referred to as, and may include some or all of the
functionality of, a terminal, an access terminal, a user equipment
(UE), a subscriber unit, a station, etc. A wireless communication
device 420 may be a cellular phone, a personal digital assistant
(PDA), a wireless device, a wireless modem, a handheld device, a
laptop computer, etc. A wireless communication device 420 may
communicate with zero, one or multiple base stations on the forward
link 423a-d and/or reverse link 424a-d at any given moment. The
forward link 423 (or downlink) refers to the communication link
from a base station to a wireless communication device 420 and the
reverse link 424 (or uplink) refers to the communication link from
a wireless communication device 420 to a base station.
[0073] A first wireless communication device 420a may be part of a
closed subscriber group (CSG) associated with the femto access
point 419. The femto access point 419 may allow access only to
wireless communication devices 420 that are part of the closed
subscriber group (CSG). With signaling only access, wireless
communication devices 420 that are not part of a closed subscriber
group (CSG) are allowed to exchange signaling messages with the
core network using the femto access point 419. However, in
signaling only access, the wireless communication devices 420 that
are not part of the closed subscriber group (CSG) are not allowed
active mode voice/data service from the femto access point 419.
[0074] The first wireless communication device 420a may switch
between communicating with a macro base station 418 and
communicating with the femto access point 419. Because the first
wireless communication device 420a is part of the closed subscriber
group (CSG) associated with the femto access point 419, it may be
desirable for the first wireless communication device 420a to
communicate with the femto access point 419 as long as coverage by
the femto access point 419 is adequate. This way, the femto access
point 419 usage may be maximized. When the first wireless
communication device 420a enters the coverage area of the femto
access point 419, the first wireless communication device 420a may
perform an idle handoff from the macro base station 418 to the
femto access point 419 so that the first wireless communication
device 420a can initiate/receive calls using the femto access point
419. An idle handoff refers to a handoff from one base station to
another when a wireless communication device 420 is not in an
active call.
[0075] When the coverage of the femto access point 419 is not
adequate for the first wireless communication device 420a, the
first wireless communication device 420a may perform an idle
handoff from the femto access point 419 to the macro base station
418. Typically, a wireless communication device 420 such as a
cdma2000 1x mobile will wake up periodically to scan forward link
423 pilot signals from other base stations. If the forward link 423
pilot signal strength from another base station is greater than the
forward link 423 pilot signal strength of the current serving base
station by a certain threshold (using hysteresis), which is
typically around 3 decibels (dB), then the wireless communication
device 420 will perform an idle handoff to the other base
station.
[0076] A deep channel fade on the forward link 423 of the femto
access point 419 to the first wireless communication device 420a
may trigger the idle handoff. If the forward link 423c signal
strength of the femto access point 419 and the forward link 423a
signal strength of the macro base station 418 have similar average
values, the first wireless communication device 420a may handoff
back and forth between the femto access point 419 and the macro
base station 418. These frequent idle handoffs can drain the
battery of the first wireless communication device 420a. Frequent
idle handoffs can also increase the network signaling load, because
the wireless communication device 420 performs a registration with
the network each time the wireless communication device 420
performs an idle handoff. To avoid frequent idle handoffs between
the femto access point 419 and the macro base station 418, the
first wireless communication device 420a may use a handoff
determination module 421a. The handoff determination module 421a is
discussed in further detail below in relation to FIG. 12.
[0077] The second wireless communication device 420b may not be
part of the closed subscriber group (CSG) associated with the femto
access point 419. However, the second wireless communication device
420b may be located nearby the femto access point 419. The second
wireless communication device 420b may receive communications from
the macro base station 418 via a forward link 423b and send
communications to the macro base station 418 via a reverse link
424b.
[0078] Like the first wireless communication device 420a, the
second wireless communication device 420b may periodically wake-up
to scan pilots from other base stations (i.e., to measure the
forward link 423d pilot signal strength from the femto access point
419 to the second wireless communication device 420b). If the
forward link 423d pilot signal strength from the femto access point
419 is greater than the forward link 423b pilot signal strength
received from the macro base station 418, the second wireless
communication device 420b may attempt an idle handoff from the
macro base station 418 to the femto access point 419. Even though
this idle handoff may be denied (because the second wireless
communication device 420b is not part of the closed subscriber
group (CSG) associated with the femto access point 419), an idle
handoff attempt may still burden network resources. To avoid
frequent idle handoff attempts between the macro base station 418
and the femto access point 419, the second wireless communication
device 420b may use a handoff determination module 421b. The
handoff determination module 421b is discussed in further detail
below in relation to FIG. 12.
[0079] The femto access point 419 may attempt to prevent frequent
idle handoffs from wireless communication devices 420 that are part
of the closed subscriber group (CSG) associated with the femto
access point 419 (i.e., the first wireless communication device
420a) and wireless communication devices 420 that are not part of
the closed subscriber group (CSG) associated with the femto access
point 419 (i.e., the second wireless communication device 420b)
using a frequent handoff reduction module 422. The frequent handoff
reduction module 422 is discussed in further detail below in
relation to FIG. 5.
[0080] Upon detecting frequent handoffs by the first wireless
communication device 420a, the frequent handoff reduction module
422 may increase the transmit power of the femto access point 419
to increase the coverage area of the femto access point 419 and
bring the first wireless communication device 420a out of the
frequent handoff cycle. Upon detecting frequent handoffs by the
second wireless communication device 420b, the frequent handoff
reduction module 422 may reduce the transmit power of the femto
access point 419 to decrease the coverage area of the femto access
point 419 and bring the second wireless communication device 420b
out of the frequent handoff cycle.
[0081] FIG. 5 is a block diagram of a frequent handoff reduction
module 522. The frequent handoff reduction module 522 of FIG. 5 is
one configuration of the frequent handoff reduction module 422 of
FIG. 4. The frequent handoff reduction module 522 may be on a femto
access point 419. The frequent handoff reduction module 522 may
include a registration attempts counter 525. The registration
attempts counter 525 may count the number 526 of registration
attempts made by one or more wireless communication devices over a
certain time period (e.g., N hours or N days).
[0082] In idle mode (no active, ongoing voice/data session), a
wireless communication device 420 (such as a cdma2000 mobile
station) will turn off all its circuitry and enter a sleep state
most of the time to conserve battery life. The wireless
communication device 420 wakes up periodically to monitor any
incoming pages from the network. When the wireless communication
device 420 wakes up, it performs intra-frequency and
inter-frequency searches to find neighboring base stations using a
list (e.g., a Neighbor List Message) provided by the current
serving base station.
[0083] Neighboring base stations on the same frequency as the
current serving base station are searched more often. Different
frequencies are searched only when the forward link 423 power ratio
Ecp/Io from the current serving base station falls below a certain
threshold (Ecp=received pilot signal power from a particular base
station, Io=total received signal power including noise). An idle
handoff registration attempt is performed if the forward link 423
power ratio Ecp/Io from a non-serving base station is better than
the forward link 423 power ratio Ecp/Io from the current serving
base station point by some hysteresis margin. Additional criteria
may be followed by the wireless communication device 420 to perform
handoff.
[0084] Every idle handoff registration attempt may not be
successful. For example, the non-serving base station may use
access constraints that prevent certain wireless communication
devices 420 (that are not part of the closed subscriber group (CSG)
associated with the non-serving base station) from performing an
idle handoff to the non-serving base station. The wireless
communication device 420 may attempt an idle handoff registration
but be denied by the non-serving base station. Idle handoff
registration attempts that are denied are still counted by the
registration attempts counter 525.
[0085] The frequent handoff reduction module 522 may also include a
registration threshold 527. The registration threshold 527 may be a
predefined threshold that limits the number 526 of registration
attempts made by a wireless communication device 420 before the
femto access point 419 takes action to reduce the frequent
handoffs. The frequent handoff reduction module 522 may include a
different registration threshold 527 for wireless communication
devices 420 that are part of the closed subscriber group (CSG)
associated with the femto access point 419 than for wireless
communication devices 420 that are not part of the closed
subscriber group (CSG).
[0086] The frequent handoff reduction module 522 may also include a
registration timer 528 with a registration time 529. The frequent
handoff reduction module 411 may count the number 526 of
registration attempts made by a wireless communication device 420
while the registration timer 528 is running and compare the number
526 of registration attempts with the registration threshold 527.
The frequent handoff reduction module 522 may then
increase/decrease a transmit power 535 of the femto access point
419 if the number of registration attempts is greater than the
registration threshold 527. When increasing/decreasing the transmit
power 535, changes may be made to the total forward link transmit
power (Ior_tx) 536 or to the forward link pilot transmit power
(Ecp_tx) 537. Changes made to the total forward link transmit power
(Ior_tx) 536 may also change the forward link pilot transmit power
(Ecp_tx) 537 because the pilot power gain is relative to the total
transmit power. As an example, in current macro base stations 418,
the forward link pilot transmit power 537 is .about.20% and the
overhead channel power is .about.15% of the total available
transmit power. The remaining power is reserved to serve a large
number of users under the macro base station 418 coverage. However,
the number of users that a femto access point 419 is likely to
serve is very limited (around four or five). Therefore, a larger
fraction of power can be allocated to pilot and overhead
channels.
[0087] The frequent handoff reduction module 522 may include a
power adjustment factor 532 and a power adjustment timer 533 with a
power adjustment time 534. The power adjustment factor 532 may be a
configurable factor that adjusts the transmit power 535 of the
femto access point 419 up or down (e.g., 2 dB up or 2 dB down). The
power adjustment factor 532 may adjust the total forward link
transmit power 536 or the forward link pilot transmit power 537.
Power adjustment factors 532 and the power adjustment timer 533 are
discussed in additional detail below in relation to FIG. 10.
[0088] FIG. 6 is a flow diagram of a method 600 for reducing
frequent handoffs. The method 600 may be performed by a femto
access point 419. The femto access point 419 may receive 602 a
registration request from a wireless communication device 420. The
wireless communication device 420 may or may not belong to a closed
subscriber group (CSG) associated with the femto access point 419.
The wireless communication device 420 may perform an idle handoff
from a macro base station 418 to the femto access point 419 by
first sending a registration request to the femto access point 419.
Upon receiving 602 the registration request, the femto access point
419 may start 604 a registration timer 528.
[0089] The femto access point 419 may count 606 the number 526 of
registration requests received from the wireless communication
device 420 during the registration time 529. Once the registration
timer 528 has expired 608, the femto access point 419 may then
determine 610 whether the number 526 of registration requests
received from the wireless communication device 420 is greater than
a registration threshold 527. If the number 526 of registration
requests received from the wireless communication device 420 is not
greater than the registration threshold 527, the femto access point
419 may wait to receive 602 another registration request from a
wireless communication device 420.
[0090] If the number 527 of registration requests received from the
wireless communication device 420 is greater than the registration
threshold 527, the femto access point 419 may adjust 612 the
transmit power 535 of the femto access point 419 accordingly. In
one configuration, adjusting 612 the transmit power 535 may include
adjusting the total forward link transmit power (Ior_tx) 536, which
also adjusts the forward link pilot transmit power (Ecp_tx) 537,
since the pilot power gain is relative to the total forward link
transmit power (Ior_tx) 536. In another configuration, adjusting
612 the transmit power 535 may include only adjusting the forward
link pilot transmit power (Ecp_tx) 537. Adjusting 612 the transmit
power 535 may include increasing and decreasing the transmit power
535.
[0091] In one configuration, the femto access point 419 may detect
active handoffs of a wireless communication device 420. Upon
detecting an active handoff (active handoffs are signaled via the
core network), the femto access point 419 may start a registration
timer 528 and count the number of active handoffs (or active
handoff attempts) by the wireless communication device 420 during
the registration time 529. If frequent active handoffs are detected
over the registration time 529, the femto access point 419 may
adjust 612 the transmit power 535.
[0092] The femto access point 419 may then determine 613 whether a
change to an idle mode pilot trigger threshold on the wireless
communication device 420 is needed. The idle mode pilot trigger
threshold is discussed in additional detail below in relation to
FIG. 12. The idle mode pilot trigger threshold may be an adjustable
threshold used by the wireless communication device 420 to
determine when to search for pilot signals from other base stations
while in idle mode. The femto access point may adjust 614 an idle
mode pilot trigger threshold on the wireless communication device
420 if a change to the idle mode pilot trigger threshold is needed.
If a change to the idle mode pilot trigger threshold on the
wireless communication device 420 is not needed, the femto access
point may return to waiting to receive 602 another registration
request from a wireless communication device 420.
[0093] Adjusting 614 the idle mode pilot trigger threshold on the
wireless communication device 420 may cause the wireless
communication device 420 to delay searches for other base stations,
thereby causing the wireless communication device 420 to stay on
the femto access point 419 longer. Thus, frequent idle handoff
effects are naturally reduced. Adjusting 614 an idle mode pilot
trigger threshold on the wireless communication device 420 may
include sending instructions to the wireless communication device
420 that include changes to the idle mode pilot trigger
threshold.
[0094] Adjusting 614 an idle mode pilot trigger threshold on the
wireless communication device 420 may be done proactively or upon
detection of frequent idle handoffs based on registration attempts.
The femto access point 419 may only adjust 614 an idle mode pilot
trigger threshold on the wireless communication device 420 if such
adjustable controls are available to the femto access point 419.
Though such capability does not exist in current cdma2000 femto
access points 419, this is likely to be available in the future.
However, this solution readily applies to WCDMA systems where
separate thresholds are provided to trigger intra-frequency or
inter-frequency pilot searches. The femto access point 419 may then
wait to receive 602 another registration request from a wireless
communication device 420.
[0095] Femto access points such as cdma2000 1x femtocells can
transmit beacons on frequencies different from the normal operating
forward link frequency when the femtocell forward link frequency is
different from the neighboring macro base station frequencies. In
such a case, a wireless communication device performs an idle
hand-in from a macro base station to a femtocell via a beacon, but
performs inter-frequency idle hand-out directly from the femtocell
to the macro base station without any beacons. Thus, to avoid
frequent handoffs, the femtocell may adjust the power level of
beacon transmissions in conjunction with adjusting the transmit
power level of the normal operating forward link frequency.
[0096] The method 600 of FIG. 6 described above may be performed by
various hardware and/or software component(s) and/or module(s)
corresponding to the means-plus-function system 700 illustrated in
FIG. 7. In other words, blocks 602 through 614 illustrated in FIG.
6 correspond to means-plus-function blocks 702 through 714
illustrated in FIG. 7. For example, system 700 can reside at least
partially within a base station, or mobile device, etc. It is to be
appreciated that system 700 is represented as including functional
blocks, which can represent functions implemented by a processor,
software, or combination thereof, such as, for example, firmware.
Additionally, the system 700 may include a memory (not shown) that
retains instructions for executing functions associated with blocks
702 through 714.
[0097] FIG. 8 is another flow diagram of a method 800 for reducing
frequent handoffs. The method 800 may be performed by a femto
access point 419. The femto access point 419 may receive 802 a
registration request from a wireless communication device 420. The
wireless communication device 420 may or may not be part of the
closed subscriber group (CSG) associated with the femto access
point 419. When a wireless communication device 420 performs idle
handoff from a macro base station 418 to a femto access point 419,
the wireless communication device 420 sends a registration request
to the femto access point 419. Upon receiving the registration
request, the femto access point 419 may start 804 a registration
timer 528.
[0098] The femto access point 419 may then count 806 the number 526
of registration requests received from the wireless communication
device 420 until the registration timer 528 expires 808. The femto
access point 419 may compare 810 the number 526 of registration
requests received from the wireless communication device 420 with a
registration threshold 527. If the number 526 of registration
requests received from the wireless communication device 420 is not
greater than the registration threshold 527, the femto access point
419 may wait to receive 802 another registration request from a
wireless communication device 420.
[0099] If the number 526 of registration requests received from the
wireless communication device 420 is greater than the registration
threshold 527, the femto access point 419 may determine 812 that
the wireless communication device 420 is performing frequent idle
handoffs. As an example, the registration time 529 can be set to
two minutes and the registration threshold 527 can be set to five.
If more than five registration attempts from the wireless
communication device 420 are detected during the two minute
registration timer 529, the femto access point 419 may determine
812 that the wireless communication device 420 is performing
frequent idle handoffs. As another example, the registration time
529 can be set to two hours and the registration threshold 527 can
be set to fifty. If more than fifty registration attempts from the
wireless communication device 420 are detected during the two hour
registration timer 529, the femto access point 419 may determine
812 that the wireless communication device 420 is performing
frequent idle handoffs. Overall, the registration timer 528 and the
registration threshold 527 can be configured and optimized to
reduce frequent handoffs.
[0100] The femto access point 419 may then determine 814 whether
the wireless communication device 420 is part of a closed
subscriber group (CSG) associated with the femto access point 419.
If the wireless communication device 420 is part of a closed
subscriber group (CSG) associated with the femto access point 419,
it may be desirable to make the wireless communication device 420
stick to the femto access point 419. In other words, it may be
desirable that the wireless communication device 420 communicate
with the femto access point 419 for as long as possible. The femto
access point 419 may thus increase 818 the transmit power 535 to
improve forward link coverage and thereby prevent frequent handoffs
of a wireless communication device 420 that is part of a closed
subscriber group (CSG) associated with the femto access point 419.
In one configuration, the femto access point 419 may increase 818
the transmit power 535 by a power adjustment factor 532. Power
adjustment factors 532 are discussed in further detail below in
relation to FIG. 10. In one configuration, the femto access point
419 may increase 818 the transmit power 535 on the forward link
pilot channel Walsh code by a few dBs.
[0101] In one configuration, the femto access point 419 may
proactively choose to adjust the transmit power 535 to adjust the
coverage area of the femto access point 419. This technique is
especially useful when femto access points 419 have a dedicated
frequency different from neighboring macro base stations 418
because a higher pilot and overhead power will not cause
interference to the macro network, but will provide good femto
access point 419 coverage to delay idle handoffs.
[0102] Depending on the available transmit power 535 headroom, the
femto access point 419 may increase the total forward link transmit
power (Ior_tx) 536 (which also increases the forward link pilot
transmit power (Ecp_tx) 537, since pilot power gain is relative to
the total transmit power) or only the forward link pilot transmit
power (Ecp_tx) 537 by adjusting the pilot channel gain. Increasing
either the total forward link transmit power (Ior_tx) 536 or only
the forward link pilot transmit power (Ecp_tx) 537 may cause
signals received by the wireless communication device 420 from a
macro base station 418 to be weaker than signals received by the
wireless communication device 420 from the femto access point 419.
This may reduce the idle handoffs of the wireless communication
device 420. The femto access point 419 may then wait to receive 802
another registration request from a wireless communication device
420.
[0103] If the wireless communication device 420 is not part of a
closed subscriber group (CSG) associated with the femto access
point 419, it may be desirable to force the wireless communication
device 420 out of the coverage area of the femto access point 419.
The femto access point 419 may thus reduce 816 the transmit power
535. The femto access point 419 may reduce the total forward link
transmit power (Ior_tx) 536 or only the forward link pilot transmit
power (Ecp_tx) 537 to force the wireless communication device 420
out of the coverage area of the femto access point 419. In one
configuration, the femto access point 419 may reduce 816 the
transmit power 535 by a power adjustment factor 532. Power
adjustment factors 532 are discussed in further detail below in
relation to FIG. 10. The femto access point 532 may then wait to
receive 802 another registration request from a wireless
communication device 420.
[0104] The method 800 of FIG. 8 described above may be performed by
various hardware and/or software component(s) and/or module(s)
corresponding to the means-plus-function system 900 illustrated in
FIG. 9. In other words, blocks 802 through 818 illustrated in FIG.
8 correspond to means-plus-function blocks 902 through 918
illustrated in FIG. 9. For example, system 900 can reside at least
partially within a base station, or mobile device, etc. It is to be
appreciated that system 900 is represented as including functional
blocks, which can represent functions implemented by a processor,
software, or combination thereof, such as, for example, firmware.
Additionally, the system 900 may include a memory (not shown) that
retains instructions for executing functions associated with blocks
902 through 918.
[0105] FIG. 10 is a flow diagram of yet another method 1000 for
reducing frequent handoffs. The method 100 may be performed by a
femto access point 419. The femto access point 419 may detect 1002
frequent idle handoffs by a wireless communication device 420. In
one configuration, the femto access point 419 may detect 1002
frequent idle handoffs by a wireless communication device 420 by
counting the number 526 of registration attempts made by the
wireless communication device 420. The femto access point 419 may
then adjust 1004 the transmit power 535 of the femto access point
419 by a power adjustment factor 532. As discussed above in
relation to FIG. 5, the femto access point 419 may increase or
decrease either the total forward link transmit power (Ior_tx) 536
or only the forward link pilot transmit power (Ecp_tx) 537. Power
is increased if wireless communication devices 420 that are part of
the closed subscriber group (CSG) associated with the femto access
point 419 are performing frequent idle handoffs, thereby improving
the forward link coverage area of the femto access point 419. Power
is decreased if wireless communication devices 420 that are not
part of the closed subscriber group (CSG) associated with the femto
access point 419 are performing frequent idle handoffs, thereby
shrinking the forward link coverage area of the femto access point
419.
[0106] Power adjustments are only done for a certain duration
(e.g., ten minutes) so as to not affect normal coverage by the
femto access point 419. Thus, the femto access point 419 may start
1006 a power adjustment timer 533 after adjusting 1004 the transmit
power of the femto access point 419 by the power adjustment factor
532. Once the power adjustment timer 533 has expired 1008, the
femto access point 419 may determine 1012 whether frequent idle
handoffs by the wireless communication device 420 were detected
while the power adjustment timer 533 was running If frequent idle
handoffs by the wireless communication device 420 were detected
while the power adjustment timer 533 was running, the femto access
point 419 may incrementally increase 1014 the power adjustment time
534 (i.e., from ten minutes to fifteen minutes, then twenty
minutes) used by the power adjustment timer 533. The femto access
point 419 may also incrementally increase 1016 the power adjustment
factor 532.
[0107] For example, if a wireless communication device 420 that is
part of the closed subscriber group (CSG) associated with the femto
access point 419 is performing frequent handoffs and power was
increased earlier by power adjustment factor=X dB prior to the
power adjustment timer 533 expiration, then the power adjustment
factor is made (X+1) dB and in effect the total transmit power is
increased further by 1 dB. If a wireless communication device 420
that is not part of the closed subscriber group (CSG) associated
with the femto access point 419 is performing frequent handoffs and
power was decreased earlier by power adjustment factor=X dB prior
to the power adjustment timer 533 expiration, then the power
adjustment factor is made (X+1) dB and so the total transmit power
is reduced further by 1 dB
[0108] Thus, the transmit power adjustment factor 532 and the
duration for which transmit power 535 is adjusted may be adapted
based on the severity of frequent handoff events. The femto access
point 419 may then again adjust 1004 the transmit power 535 of the
femto access point 419 by the power adjustment factor 532.
[0109] If frequent idle handoffs by the wireless communication
device 420 were not detected while the power adjustment timer 533
was running, the femto access point 419 may incrementally decrease
1018 the power adjustment time 534 used by the power adjustment
timer 533. The femto access point 419 may also incrementally
decrease 1020 the power adjustment factor 532.
[0110] For example, a wireless communication 420 that is part of
the closed subscriber group (CSG) associated with the femto access
point 419 was performing frequent idle handoffs and power was
increased earlier by power adjustment factor=X dB prior to the
power adjustment timer 533 expiration. If this wireless
communication device 420 does not perform frequent idle handoffs
when the power adjustment timer 533 is running then the power
adjustment factor is made (X-1) dB and so the new total transmit
power is reduced by 1 dB.
[0111] The femto access point 419 may readjust 1022 the transmit
power to the previous transmit power level. The femto access point
419 may then wait to detect 1002 frequent idle handoffs by a
wireless communication device 420.
[0112] The method 1000 of FIG. 10 described above may be performed
by various hardware and/or software component(s) and/or module(s)
corresponding to the means-plus-function system 1100 illustrated in
FIG. 11. In other words, blocks 1002 through 1022 illustrated in
FIG. 10 correspond to means-plus-function blocks 1102 through 1122
illustrated in FIG. 11. For example, system 1100 can reside at
least partially within a base station, or mobile device, etc. It is
to be appreciated that system 1100 is represented as including
functional blocks, which can represent functions implemented by a
processor, software, or combination thereof, such as, for example,
firmware. Additionally, the system 1100 may include a memory (not
shown) that retains instructions for executing functions associated
with blocks 1102 through 1122.
[0113] In one configuration, the femto access point 419 can adjust
the transmit power 535 according to the time of the day. For
example, a femto access point 419 can learn that preferred users
(i.e., wireless communication devices 420 that are part of the
closed subscriber group (CSG) associated with the femto access
point 419) are out of the home during regular business hours,
allowing the femto access point 419 to reduce the transmit power
535 to limit handoffs/registrations by non-preferred users during
regular business hours.
[0114] FIG. 12 is a block diagram illustrating a handoff
determination module 1421. The handoff determination module 1421 of
FIG. 12 may be one configuration of the handoff determination
modules 421 a-b of FIG. 4. The handoff determination module 1421
may be located on a wireless communication device 420 (i.e., the
first wireless communication device 420 or the second wireless
communication device 420).
[0115] The handoff determination module 1421 may include an
observation threshold 1450. The observation threshold 1450 may be a
predefined threshold that is used by the handoff determination
module 1421 to determine when to delay idle handoffs. The handoff
determination module 1421 may also include an observation timer
1451 with an observation time 1452.
[0116] The handoff determination module 1421 may include a
registration attempts counter 1453 that counts the number 1454 of
registration attempts/requests by the wireless communication device
420 to a femto access point 419. If the number 1454 of
registrations attempted by a wireless communication device 420
during the observation time 1452 is greater than the observation
threshold 1450, the handoff determination module 1421 may delay
idle handoffs away from the femto access point 419 (i.e., idle
handout) for a handout time 1457 using a handout timer 1456. In one
configuration, the handout time 1457 may be between two and five
minutes. This mechanism is discussed in further detail below in
relation to FIG. 13.
[0117] The handoff determination module 1421 may include a handout
threshold 1455. The handout threshold 1455 may be a predefined
threshold that is used by the handoff determination module 1421 to
determine when to handoff from the femto access point 419. For
example, the handout threshold 1455 may be set to -15 dB or another
appropriate value at which the wireless communication device 420
can still receive service from the femto access point 419 with
reasonably good quality. Unless the power level of signals received
from the femto access point 419 falls below the handout threshold
1455 during the handout time 1457, the handoff determination module
1421 may prevent the wireless communication device 420 from
performing an idle handoff away from the femto access point
419.
[0118] The handoff determination module 1421 may include an idle
mode pilot search trigger threshold 1430. Idle mode pilot search
trigger thresholds 1430 were discussed above in relation to FIG. 6.
An idle mode pilot search trigger threshold 1430 may determine the
amount of time a wireless communication device 420 waits before
searching for pilot signals from other base stations. In one
configuration, the idle mode pilot search trigger threshold 1430
may reflect a minimum increase in received pilot power from a
non-serving base station over the received pilot power from a
current serving base station before an idle handoff is triggered to
leave the current serving base station and handoff to the
non-serving base station.
[0119] The wireless communication device 420 may receive
instructions from a femto access point 419 to adjust the idle mode
pilot search trigger threshold 1430. In one configuration, the
instructions to adjust the idle mode pilot search trigger threshold
1430 may include the specific adjustments to be made to the idle
mode pilot search trigger threshold 1430. The wireless
communication device 420 may determine whether changes are needed
to the idle mode pilot search trigger threshold 1430. In one
configuration, determining whether changes are needed to the idle
mode pilot search trigger threshold 1430 may include determining
whether instructions to adjust the idle mode pilot search trigger
threshold 1430 were received from a femto access point 419.
[0120] FIG. 13 is a flow diagram of a method 1500 for reducing
handoffs by a wireless communication device 420. The method 1500
may be performed by the wireless communication device 420. The
wireless communication device 420 may or may not be part of a
closed subscriber group (CSG) associated with a femto access point
419. The wireless communication device 420 may be able to
distinguish between femto access point 419 pilot and macro base
station 418 pilot signatures (PNs).
[0121] The wireless communication device 420 may send 1502 a
registration request to the femto access point 419. In one
configuration, sending 1502 a registration request to the femto
access point 419 may be part of performing registration to the
femto access point 419. If the wireless communication device 420 is
not part of the closed subscriber group (CSG) associated with the
femto access point 419, the registration to the femto access point
419 may fail. Alternatively, the wireless communication device 420
may be granted limited access to the femto access point 419.
[0122] The wireless communication device 420 may start 1504 an
observation timer 1451. The wireless communication device 420 may
then count 1506 the number 1454 of registrations attempts to the
femto access point 419. The number 1454 of registration attempts to
the femto access point 419 may include both successful
registrations and failed registration attempts. The observation
timer 1451 may expire 1508 after the observation time 1452 has
elapsed. The wireless communication device 420 may then detect 1510
a trigger for an idle handoff away from the femto access point 419.
The wireless communication device 420 may determine 1512 whether
the number 1454 of registrations attempted to the femto access
point 419 is greater than an observation threshold 1450.
[0123] If the number 1454 of registrations performed to the femto
access point 419 is greater than the observation threshold 1450,
the wireless communication device 420 has detected a frequent
handoff condition. The wireless communication device 420 may start
1516 a handout timer 1456. The wireless communication device 420
may then determine 1518 whether the forward link pilot received
power (Ecp/Io) from the femto access point 419 is above a handout
threshold 1455.
[0124] If the forward link pilot received power (Ecp/Io) from the
femto access point 419 is above the handout threshold 1455, the
wireless communication device 420 may determine 1520 whether the
handout timer 1456 has expired. If the handout timer 1456 has not
expired, the wireless communication device 420 may return to
determining 1518 if the forward link pilot received power (Ecp/Io)
from the femto access point 419 is above the handout threshold
1455.
[0125] If the handout timer 1456 has expired, the wireless
communication device 420 may determine 1522 whether the handout
trigger condition was satisfied within a monitoring period. In
other words, the wireless communication device 420 may determine
whether the conditions that triggered the idle handoff away from
the femto access point 419 still indicate that an idle handoff away
from the femto access point 419 is necessary. If the handout
trigger condition was satisfied within a monitoring period, the
wireless communication device 420 may perform 1514 the idle handoff
away from the femto access point 419. If the handout trigger
condition was not satisfied within a monitoring period, the
wireless communication device 420 may stay 1524 on the femto access
point 419.
[0126] If the forward link pilot received power (Ecp/Io) from the
femto access point 419 falls below the handout threshold 1455, the
wireless communication device 420 may perform 1514 the idle handoff
away from the femto access point 419 without further delay. If the
number 1454 of registrations attempted by the wireless
communication device 420 to the femto access point 419 is not
greater than the observation threshold 1450, the wireless
communication device 420 may perform 1514 the idle handoff away
from the femto access point 419 without any delay.
[0127] The method 1500 of FIG. 13 described above may be performed
by various hardware and/or software component(s) and/or module(s)
corresponding to the means-plus-function system 1600 illustrated in
FIG. 14. In other words, blocks 1502 through 1524 illustrated in
FIG. 13 correspond to means-plus-function blocks 1602 through 1624
illustrated in FIG. 14. For example, system 1600 can reside at
least partially within a base station, or mobile device, etc. It is
to be appreciated that system 1600 is represented as including
functional blocks, which can represent functions implemented by a
processor, software, or combination thereof, such as, for example,
firmware. Additionally, the system 1600 may include a memory (not
shown) that retains instructions for executing functions associated
with blocks 1602 through 1624.
[0128] FIG. 17 is a flow diagram of another method 1700 for
reducing frequent handoffs by a wireless communication device 420.
The method 1700 may be performed by the wireless communication
device 420. The wireless communication device 420 may or may not be
part of a closed subscriber group (CSG) associated with a femto
access point 419.
[0129] The wireless communication device 420 may send 1702 a
registration request to the femto access point 419. In one
configuration, sending 1702 a registration request to the femto
access point 419 may be part of performing registration to the
femto access point 419. The wireless communication device 420 may
detect 1704 a trigger for an idle handoff away from the femto
access point 419. The wireless communication device 420 may then
start 1706 a handout timer 1456. The wireless communication device
420 may determine 1708 whether the forward link pilot received
power (Ecp/Io) from the femto access point 419 is below a handout
threshold 1455. As an example, the handout threshold 1455 may be a
received power of -15 dB (below which overhead channels may not be
decoded successfully).
[0130] If the forward link pilot received power (Ecp/Io) from the
femto access point 419 is below the handout threshold 1455, the
wireless communication device 420 may perform 1710 an idle handoff
away from the femto access point 419. If the forward link pilot
received power (Ecp/Io) from the femto access point 419 is not
below the handout threshold 1455, the wireless communication device
420 may determine 1712 whether the handout timer 1456 has expired.
If the handout timer 1456 has not expired, the wireless
communication device may return to detecting 1704 a trigger for an
idle handoff away from the femto access point 419.
[0131] If the handout timer 1456 has expired, the wireless
communication device 420 may determine 1714 whether the handout
trigger condition was satisfied within a monitoring period. In
other words, the wireless communication device 420 may determine
whether conditions are such that an idle handoff away from the
femto access point 419 is still necessary (i.e., triggered). If the
handout condition is satisfied within a monitoring period, the
wireless communication device 420 may stay 1716 on the femto access
point 419. If the handout condition is not satisfied within a
monitoring period, the wireless communication device 420 may
perform 1710 an idle handoff away from the femto access point 419.
Thus, the method 1700 simply delays idle handoffs based on the
handout timer 1456, irrespective of whether frequent handoffs are
occurring.
[0132] The method 1700 of FIG. 15 described above may be performed
by various hardware and/or software component(s) and/or module(s)
corresponding to the means-plus-function system 1800 illustrated in
FIG. 16. In other words, blocks 1702 through 1716 illustrated in
FIG. 15 correspond to means-plus-function blocks 1802 through 1816
illustrated in FIG. 16. For example, system 1800 can reside at
least partially within a base station, or mobile device, etc. It is
to be appreciated that system 1800 is represented as including
functional blocks, which can represent functions implemented by a
processor, software, or combination thereof, such as, for example,
firmware. Additionally, the system 1800 may include a memory (not
shown) that retains instructions for executing functions associated
with blocks 1802 through 1816.
[0133] FIG. 17 illustrates two wireless devices in a multiple-in
and multiple-out (MIMO) system 1900. A MIMO system 1900 employs
multiple (N.sub.T) transmit antennas 1924 and multiple (N.sub.R)
receive antennas 1952 for data transmission. A MIMO channel formed
by the N.sub.T transmit and N.sub.R receive antennas may be
decomposed into N.sub.S independent channels, which are also
referred to as spatial channels, where N.sub.S<min{N.sub.T,
N.sub.R}. Each of the N.sub.S independent channels corresponds to a
dimension. The MIMO system may provide improved performance (e.g.,
higher throughput and/or greater reliability) if the additional
dimensionalities created by the multiple transmit and receive
antennas are utilized.
[0134] A MIMO system 1900 may support time division duplex ("TDD")
and frequency division duplex ("FDD"). In a TDD system, the forward
and reverse link transmissions are on the same frequency region so
that the reciprocity principle allows the estimation of the forward
link channel from the reverse link channel. This enables a
transmitting wireless device 1910 to extract transmit beamforming
gain on the forward link when multiple antennas are available at
the receiving wireless device 1950.
[0135] The teachings herein may be incorporated into a node (e.g.,
a device) employing various components for communicating with at
least one other node. At the transmitting device 1910, traffic data
for a number of data streams is provided from a data source 1912 to
a transmit ("TX") data processor 1914.
[0136] In some aspects, each data stream is transmitted over a
respective transmit antenna. The TX data processor 1914 formats,
codes and interleaves the traffic data for each data stream based
on a particular coding scheme selected for that data stream to
provide coded data.
[0137] The coded data for each data stream may be multiplexed with
pilot data using OFDM techniques. The pilot data is typically a
known data pattern that is processed in a known manner and may be
used at the receiver system to estimate the channel response. The
multiplexed pilot and coded data for each data stream is then
modulated (i.e., symbol mapped) based on a particular modulation
scheme (e.g., BPSK, QSPK, M-PSK, or M-QAM) selected for that data
stream to provide modulation symbols. The data rate, coding and
modulation for each data stream may be determined by instructions
performed by a processor 1930. A data memory 1932 may store program
code, data and other information used by the processor 1930 or
other components of the device 1910.
[0138] The modulation symbols for all data streams are then
provided to a TX MIMO processor 1920, which may further process the
modulation symbols (e.g., for OFDM). The TX MIMO processor 1920
then provides N.sub.T modulation symbol streams to N.sub.T
transceivers ("XCVR") 1922A through 1922T. In some aspects, the TX
MIMO processor 1920 applies beamforming weights to the symbols of
the data streams and to the antenna from which the symbol is being
transmitted.
[0139] Each transceiver 1922 receives and processes a respective
symbol stream to provide one or more analog signals, and further
conditions (e.g., amplifies, filters and upconverts) the analog
signals to provide a modulated signal suitable for transmission
over the MIMO channel. N.sub.T modulated signals from transceivers
1922A through 1922T are then transmitted from N.sub.T antennas
1924A through 1924T, respectively.
[0140] At the receiving wireless device 1950, the transmitted
modulated signals are received by N.sub.R antennas 1952A through
1952R and the received signal from each antenna 1952 is provided to
a respective transceiver ("XCVR") 1954A through 1954R. Each
transceiver 1954 conditions (e.g., filters, amplifies and
downconverts) a respective received signal, digitizes the
conditioned signal to provide samples and further processes the
samples to provide a corresponding "received" symbol stream.
[0141] A receive ("RX") data processor 1960 then receives and
processes the N.sub.R received symbol streams from N.sub.R
transceivers 1954 based on a particular receiver processing
technique to provide N.sub.T "detected" symbol streams. The RX data
processor 1960 then demodulates, deinterleaves and decodes each
detected symbol stream to recover the traffic data for the data
stream. The processing by the RX data processor 1960 is
complementary to that performed by the TX MIMO processor 1920 and
the TX data processor 1914 at the transmitting wireless device
1910.
[0142] A processor 1970 periodically determines which pre-coding
matrix to use (discussed below). The processor 1970 formulates a
reverse link message comprising a matrix index portion and a rank
value portion. A data memory 1972 may store program code, data and
other information used by the processor 1970 or other components of
the device 1950.
[0143] The reverse link message may comprise various types of
information regarding the communication link and/or the received
data stream. The reverse link message is then processed by a TX
data processor 1938, which also receives traffic data for a number
of data streams from a data source 1936, modulated by a modulator
1980, conditioned by the transceivers 1954A through 1954R and
transmitted back to the device 1910.
[0144] At the device 1910, the modulated signals from the device
1950 are received by the antennas 1924, conditioned by the
transceivers 1922, demodulated by a demodulator ("DEMOD") 1940 and
processed by a RX data processor 1942 to extract the reverse link
message transmitted by the device 1950. The processor 1930 then
determines which pre-coding matrix to use for determining the
beam-forming weights then processes the extracted message.
[0145] FIG. 18 illustrates certain components that may be included
within a femto access point 2019. A femto access point 2019 may
also be referred to as, and may include some or all of the
functionality of, a femtocell, a picocell, a home NodeB (HNB), a
home evolved NodeB (HeNB), etc. The femto access point 2019
includes a processor 2003. The processor 2003 may be a general
purpose single- or multi-chip microprocessor (e.g., an ARM), a
special purpose microprocessor (e.g., a digital signal processor
(DSP)), a microcontroller, a programmable gate array, etc. The
processor 2003 may be referred to as a central processing unit
(CPU). Although just a single processor 2003 is shown in the femto
access point 2019 of FIG. 18, in an alternative configuration, a
combination of processors (e.g., an ARM and DSP) could be used.
[0146] The femto access point 2019 also includes memory 2005. The
memory 2005 may be any electronic component capable of storing
electronic information. The memory 2005 may be embodied as random
access memory (RAM), read-only memory (ROM), magnetic disk storage
media, optical storage media, flash memory devices in RAM, on-board
memory included with the processor, EPROM memory, EEPROM memory,
registers, and so forth, including combinations thereof.
[0147] Data 2007 and instructions 2009 may be stored in the memory
2005. The instructions 2009 may be executable by the processor 2003
to implement the methods disclosed herein. Executing the
instructions 2009 may involve the use of the data 2007 that is
stored in the memory 2005. When the processor 2003 executes the
instructions 2009, various portions of the instructions 2009a may
be loaded onto the processor 2003, and various pieces of data 2007a
may be loaded onto the processor 2003.
[0148] The femto access point 2019 may also include a transmitter
2011 and a receiver 2013 to allow transmission and reception of
signals to and from the femto access point 2019. The transmitter
2011 and receiver 2013 may be collectively referred to as a
transceiver 2015. An antenna 2017 may be electrically coupled to
the transceiver 2015. The femto access point 2019 may also include
(not shown) multiple transmitters, multiple receivers, multiple
transceivers and/or additional antennas.
[0149] The various components of the femto access point 2019 may be
coupled together by one or more buses, which may include a power
bus, a control signal bus, a status signal bus, a data bus, etc.
For the sake of clarity, the various buses are illustrated in FIG.
18 as a bus system 2021.
[0150] FIG. 19 illustrates certain components that may be included
within a wireless communication device 2120. The wireless
communication device 2120 may be an access terminal, a mobile
station, a user equipment (UE), etc. The wireless communication
device 2120 includes a processor 2103. The processor 2103 may be a
general purpose single- or multi-chip microprocessor (e.g., an
ARM), a special purpose microprocessor (e.g., a digital signal
processor (DSP)), a microcontroller, a programmable gate array,
etc. The processor 2103 may be referred to as a central processing
unit (CPU). Although just a single processor 2103 is shown in the
wireless communication device 2120 of FIG. 19, in an alternative
configuration, a combination of processors (e.g., an ARM and DSP)
could be used.
[0151] The wireless communication device 2120 also includes memory
2105. The memory 2105 may be any electronic component capable of
storing electronic information. The memory 2105 may be embodied as
random access memory (RAM), read-only memory (ROM), magnetic disk
storage media, optical storage media, flash memory devices in RAM,
on-board memory included with the processor, EPROM memory, EEPROM
memory, registers, and so forth, including combinations
thereof.
[0152] Data 2107 and instructions 2109 may be stored in the memory
2105. The instructions 2109 may be executable by the processor 2103
to implement the methods disclosed herein. Executing the
instructions 2109 may involve the use of the data 2107 that is
stored in the memory 2105. When the processor 2103 executes the
instructions 2109, various portions of the instructions 2109a may
be loaded onto the processor 2103, and various pieces of data 2107a
may be loaded onto the processor 2103.
[0153] The wireless communication device 2120 may also include a
transmitter 2111 and a receiver 2113 to allow transmission and
reception of signals to and from the wireless communication device
2106. The transmitter 2111 and receiver 2113 may be collectively
referred to as a transceiver 2115. An antenna 2117 may be
electrically coupled to the transceiver 2115. The wireless
communication device 2120 may also include (not shown) multiple
transmitters, multiple receivers, multiple transceivers and/or
additional antennas.
[0154] The various components of the wireless communication device
2120 may be coupled together by one or more buses, which may
include a power bus, a control signal bus, a status signal bus, a
data bus, etc. For the sake of clarity, the various buses are
illustrated in FIG. 19 as a bus system 2121.
[0155] The techniques described herein may be used for various
communication systems, including communication systems that are
based on an orthogonal multiplexing scheme. Examples of such
communication systems include Orthogonal Frequency Division
Multiple Access (OFDMA) systems, Single-Carrier Frequency Division
Multiple Access (SC-FDMA) systems, and so forth. An OFDMA system
utilizes orthogonal frequency division multiplexing (OFDM), which
is a modulation technique that partitions the overall system
bandwidth into multiple orthogonal sub-carriers. These sub-carriers
may also be called tones, bins, etc. With OFDM, each sub-carrier
may be independently modulated with data. An SC-FDMA system may
utilize interleaved FDMA (IFDMA) to transmit on sub-carriers that
are distributed across the system bandwidth, localized FDMA (LFDMA)
to transmit on a block of adjacent sub-carriers, or enhanced FDMA
(EFDMA) to transmit on multiple blocks of adjacent sub-carriers. In
general, modulation symbols are sent in the frequency domain with
OFDM and in the time domain with SC-FDMA.
[0156] The term "determining" encompasses a wide variety of actions
and, therefore, "determining" can include calculating, computing,
processing, deriving, investigating, looking up (e.g., looking up
in a table, a database or another data structure), ascertaining and
the like. Also, "determining" can include receiving (e.g.,
receiving information), accessing (e.g., accessing data in a
memory) and the like. Also, "determining" can include resolving,
selecting, choosing, establishing and the like.
[0157] The phrase "based on" does not mean "based only on," unless
expressly specified otherwise. In other words, the phrase "based
on" describes both "based only on" and "based at least on."
[0158] The term "processor" should be interpreted broadly to
encompass a general purpose processor, a central processing unit
(CPU), a microprocessor, a digital signal processor (DSP), a
controller, a microcontroller, a state machine, and so forth. Under
some circumstances, a "processor" may refer to an application
specific integrated circuit (ASIC), a programmable logic device
(PLD), a field programmable gate array (FPGA), etc. The term
"processor" may refer to a combination of processing 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.
[0159] The term "memory" should be interpreted broadly to encompass
any electronic component capable of storing electronic information.
The term memory may refer to various types of processor-readable
media such as random access memory (RAM), read-only memory (ROM),
non-volatile random access memory (NVRAM), programmable read-only
memory (PROM), erasable programmable read-only memory (EPROM),
electrically erasable PROM (EEPROM), flash memory, magnetic or
optical data storage, registers, etc. Memory is said to be in
electronic communication with a processor if the processor can read
information from and/or write information to the memory. Memory
that is integral to a processor is in electronic communication with
the processor.
[0160] The terms "instructions" and "code" should be interpreted
broadly to include any type of computer-readable statement(s). For
example, the terms "instructions" and "code" may refer to one or
more programs, routines, sub-routines, functions, procedures, etc.
"Instructions" and "code" may comprise a single computer-readable
statement or many computer-readable statements.
[0161] The functions described herein may be implemented in
software or firmware being executed by hardware. The functions may
be stored as one or more instructions on a computer-readable
medium. The terms "computer-readable medium" or "computer-program
product" refers to any tangible storage medium that can be accessed
by a computer or a processor. By way of example, and not
limitation, a computer-readable medium may 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. Disk and disc, as used herein, includes compact disc
(CD), laser disc, optical disc, digital versatile disc (DVD),
floppy disk and Blu-ray.RTM. disc where disks usually reproduce
data magnetically, while discs reproduce data optically with
lasers.
[0162] The methods disclosed herein comprise one or more steps or
actions for achieving the described method. The method steps and/or
actions may be interchanged with one another without departing from
the scope of the claims. In other words, unless a specific order of
steps or actions is required for proper operation of the method
that is being described, the order and/or use of specific steps
and/or actions may be modified without departing from the scope of
the claims.
[0163] Further, it should be appreciated that modules and/or other
appropriate means for performing the methods and techniques
described herein, such as those illustrated by FIGS. 6, 8, 10, 13
and 15, can be downloaded and/or otherwise obtained by a device.
For example, a device may be coupled to a server to facilitate the
transfer of means for performing the methods described herein.
Alternatively, various methods described herein can be provided via
a storage means (e.g., random access memory (RAM), read-only memory
(ROM), a physical storage medium such as a compact disc (CD) or
floppy disk, etc.), such that a device may obtain the various
methods upon coupling or providing the storage means to the
device.
[0164] It is to be understood that the claims are not limited to
the precise configuration and components illustrated above. Various
modifications, changes and variations may be made in the
arrangement, operation and details of the systems, methods, and
apparatus described herein without departing from the scope of the
claims.
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