U.S. patent application number 12/248705 was filed with the patent office on 2009-04-16 for system and method for storing information to locate a femto cell.
This patent application is currently assigned to QUALCOMM Incorporated. Invention is credited to Aleksandar M. Gogic, Rajarshi Gupta.
Application Number | 20090098885 12/248705 |
Document ID | / |
Family ID | 40534744 |
Filed Date | 2009-04-16 |
United States Patent
Application |
20090098885 |
Kind Code |
A1 |
Gogic; Aleksandar M. ; et
al. |
April 16, 2009 |
SYSTEM AND METHOD FOR STORING INFORMATION TO LOCATE A FEMTO
CELL
Abstract
A system, method and computer product for augmenting a user's
equipment (UE) database with information measured by a femto cell,
the method comprising: (a) performing RF measurements by a femto
cell; (b) connecting the UE to the femto cell; (c) downloading the
RF measurements taken by the femto cell into the UE custom
database; (d) maintaining a central database of femto cell
measurements, to be used for updating custom UE databases; (e)
comparing current RF measurements taken by the UE with the femto
cell own RF measurements to estimate proximity to the femto
cell.
Inventors: |
Gogic; Aleksandar M.; (San
Diego, CA) ; Gupta; Rajarshi; (Santa Clara,
CA) |
Correspondence
Address: |
QUALCOMM INCORPORATED
5775 MOREHOUSE DR.
SAN DIEGO
CA
92121
US
|
Assignee: |
QUALCOMM Incorporated
San Diego
CA
|
Family ID: |
40534744 |
Appl. No.: |
12/248705 |
Filed: |
October 9, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60979799 |
Oct 12, 2007 |
|
|
|
Current U.S.
Class: |
455/456.1 |
Current CPC
Class: |
H04W 64/00 20130101;
H04W 48/20 20130101; H04J 11/0069 20130101; H04W 4/029 20180201;
H04W 84/045 20130101; H04W 4/02 20130101; Y02D 30/70 20200801 |
Class at
Publication: |
455/456.1 |
International
Class: |
H04W 64/00 20090101
H04W064/00 |
Claims
1. A method for augmenting a user's equipment (UE) database, the
method comprising: performing radio frequency (RF) measurements by
a femto cell to determine a location of the femto cell; connecting
the UE to the femto cell; and downloading the RF measurements taken
by the femto cell pertaining to the location of the femto cell into
the UE database.
2. The method of claim 1, further comprising: taking RF
measurements by the UE; and comparing current RF measurements taken
by the UE with the femto cell's own RF measurements to estimate
proximity to the femto cell.
3. The method of claim 1, wherein the location of the femto cell
comprises of macro cell system parameters: within the area
described by a base station (BS) set C, in which pilots exceed
threshold E.sub.C/Io vector D, and have a mean pilot phase vector P
within tolerance Q.
4. The method of claim 1, wherein the communication of the RF
measurements between the femto cell and the UE uses an over-the-air
protocol.
5. A user's equipment (UE) comprising: a database of femto cells
acquired by the UE, individualized for the UE and stored on the UE;
wherein a femto cell takes RF measurements, downloads these RF
measurements into the UE's database when the UE is connected to the
femto cell, wherein the RF measurements pertaining to a location of
the femto cell.
6. The user's equipment (UE) of claim 5, wherein the UE takes RF
measurements and compares current RF measurements taken by the UE
with the femto cell's own measurements to estimate proximity to the
femto cell.
7. The user's equipment (UE) of claim 5, wherein the location of
the femto cell comprises macro cell system parameters, within the
area described by a base station (BS) set C, in which pilots exceed
threshold E.sub.C/Io vector D, and have a mean pilot phase vector P
within tolerance Q.
8. The user's equipment (UE) of claim 5, wherein the communication
of the RF measurements between the femto cell and the UE uses a
protocol.
9. A computer program product comprising: a computer readable
medium comprising: code for causing at least one computer to
perform RF measurements by a femto cell to determine a location of
a femto cell; code for causing at least one computer to connect the
UE to the femto cell; and code for causing at least one computer to
download the RF measurements taken by the femto cell pertaining to
the location of the femto cell into the UE database.
10. The computer program product of claim 9, wherein said computer
readable medium further comprises: code for causing at least one
computer to take RF measurements by the UE; and code for causing at
least one computer to compare current RF measurements taken by the
UE with the femto cell's own RF measurements to estimate proximity
to the femto cell.
11. The computer program product of claim 9, wherein the location
of the femto cell comprises of macro cell system parameters: within
the area described by a base station (BS) set C, in which pilots
exceed threshold E.sub.C/Io vector D, and have a mean pilot phase
vector P within tolerance Q.
12. The computer program product of claim 9, wherein the
communication of the RF measurements between the femto cell and the
UE uses an over-the-air protocol.
13. An apparatus for augmenting a user's equipment (UE) database,
comprising: means for performing RF measurements by a femto cell to
determine a location of the femto cell; means for connecting the UE
to the femto cell; and means for downloading the RF measurements
taken by the femto cell pertaining to the location of the femto
cell into the UE database.
14. The apparatus of claim 13, further comprising: means for taking
RF measurements by the UE; and means for comparing current RF
measurements taken by the UE with the femto cell's own RF
measurements to estimate proximity to the femto cell.
15. The apparatus of claim 13, wherein the location of the femto
cell comprises of macro cell system parameters: within the area
described by a base station (BS) set C, in which pilots exceed
threshold E.sub.C/Io vector D, and have a mean pilot phase vector P
within tolerance Q.
16. The apparatus of claim 13, wherein the communication of the RF
measurements between the femto cell and the UE uses an over-the-air
protocol.
17. A method for augmenting a user's equipment (UE) database for
locating femto cells, the method comprising: performing RF
measurements by a plurality of UEs, wherein RF measurements
determine a location of a femto cell based on the UE's location
relative to at least one macro cell; sending the location
information from the UEs to a back-end server; processing at the
back-end server the locations to average location for the femto
cell; connecting a UE to the back-end server; and downloading the
average location for the femto cell into the UE's database.
18. The method of claim 17, wherein the communication of the
locations between the back-end server and the UE uses an
application running over the existing internet protocol used by the
femto cell.
19. The method of claim 17, wherein the location of the femto cell
comprises macro cell system parameters, within the area described
by a base station (BS) set C, in which pilots exceed threshold
E.sub.C/Io vector D, and have a mean pilot phase vector P within
tolerance Q.
20. A system for augmenting a user's equipment (UE) database for
locating femto cells, the system comprising: a plurality of user's
equipment (UEs'); a database of femto cells acquired by the UE,
individualized for the UE and stored on the UE; a back-end server
comprising part of a macro cell mobile network; wherein the UEs
perform RF measurements, wherein RF measurements determine a
location of a femto cell based on UE's location relative to at
least one macro cell; wherein the UEs send the location information
to the back-end server; wherein the back-end server processes the
locations to average location for a femto cell; wherein the UE
connects to the back-end server; and wherein the back-end server
downloads the average location for the femto cell into the UE's
database.
21. The system of claim 20, wherein the communication of the
locations between the back-end server and the UE comprises an
application running over the existing internet protocol used by the
femto cell.
22. The system of claim 20, wherein the location of the femto cell
comprises macro cell system parameters: within the area described
by a base station (BS) set C, in which pilots exceed threshold
E.sub.C/Io vector D, and have a mean pilot phase vector P within
tolerance Q.
23. A computer program product comprising: a computer readable
medium comprising code for causing at least one computer to perform
RF measurements by an UE; code for causing at least one computer to
perform RF measurements by a plurality of UE, wherein RF
measurements determine a location of a femto cell based on UE's
location relative to at least one macro cell; code for causing at
least one computer to send the location information from the UEs to
a back-end server; code for causing at least one computer to
process at the back-end server the locations to average location
for a femto cell; code for causing at least one computer to connect
the UE to the back-end server; and code for causing at least one
computer to download the average location for the femto cell into
the UE's database.
24. The computer program product of claim 23, wherein the
communication of the locations between the back-end server and the
UE uses an application running over the existing internet protocol
used by the femto cell.
25. The computer program product of claim 23, wherein the location
of the femto cell comprises macro cell system parameters, within
the area described by a base station (BS) set C, in which pilots
exceed threshold E.sub.C/Io vector D, and have a mean pilot phase
vector P within tolerance Q.
26. An apparatus for augmenting a user's equipment (UE) database
for locating femto cells, the method comprising: means for
performing RF measurements by a plurality of UEs, wherein RF
measurements determine a location of a femto cell based on the UE's
location relative to at least one macro cell; means for sending the
location information from the UEs to a back-end server; means for
processing at the back-end server the locations to average location
for the femto cell; means for connecting a UE to the back-end
server; and means for downloading the average location for the
femto cell into the UE's database.
27. The apparatus of claim 26, wherein the communication of the
locations between the back-end server and the UE uses an
application running over the existing internet protocol used by the
femto cell.
28. The apparatus of claim 26, wherein the location of the femto
cell comprises macro cell system parameters, within the area
described by a base station (BS) set C, in which pilots exceed
threshold E.sub.C/Io vector D, and have a mean pilot phase vector P
within tolerance Q.
29. A method for augmenting a user's equipment (UE) database, the
method comprising: storing by the UE RF measurements to neighboring
macro cells at the time when the UE receives a strongest signal
from a femto cell, wherein the strongest signal corresponds to a
closest location of the femto cell; performing by the UE RF
measurements pertaining to a macro cell phase offset; and
downloading into the UE's database the information pertaining to
changes in macro cell environment.
30. The method of claim 29, further comprising re-writing the entry
into the UE's database every time the UE samples a stronger signal
from the femto cell.
31. The method of claim 29, wherein the RF measurements at the
femto cell are used to trigger error conditions at the UE, if there
is a wide divergence in the measurements reported by an associated
UE and gets erased from the UE's database.
32. A system for augmenting a user's equipment (UE) database, the
system comprising: a user's equipment (UE); a database of
neighboring macro cells acquired by the UE while visiting a
neighborhood and stored in the UE's database; wherein the UE stores
the RF measurements to neighboring macro cells at the time when the
UE receives the strongest signal from a femto cell, wherein the
strongest signal corresponds to the closest location of the femto
cell; wherein the UE performs the RF measurements pertaining to a
macro cell phase offsets; and downloads into the UE's database the
information pertaining to changes in macro cell environment.
33. The system of claim 32, wherein the UE re-writes the entry into
the UE's database time every time the UE samples a stronger signal
from the femto cell.
34. The system of claim 32, wherein the RF measurements at the
femto cell are used to trigger error conditions at the UE, if there
is a wide divergence in the measurements reported by an associated
UE and gets erased from the UE's database.
35. A computer-program product, comprising: a computer-readable
medium comprising code for causing at least one computer to store,
by the UE, the RF measurements to neighboring macro cells at the
time when the UE receives the strongest signal from a femto cell,
wherein the strongest signal corresponds to the closest location of
the femto cell; code for causing at least one computer to perform,
by the UE, RF measurements pertaining to a macro cell phase offset;
and code for causing at least one computer to download into the
UE's database the information pertaining to changes in macro cell
environment.
36. An apparatus for augmenting a user's equipment (UE) database,
comprising: means for storing by the UE RF measurements to
neighboring macro cells at the time when the UE receives a
strongest signal from a femto cell, wherein the strongest signal
corresponds to a closest location of the femto cell; means for
performing by the UE RF measurements pertaining to a macro cell
phase offset; and means for downloading into the UE's database the
information pertaining to changes in macro cell environment.
37. The apparatus of claim 36, further comprising means for
re-writing the entry into the UE's database every time the UE
samples a stronger signal from the femto cell.
38. The apparatus of claim 36, wherein the RF measurements at the
femto cell are used to trigger error conditions at the UE, if there
is a wide divergence in the measurements reported by an associated
UE and gets erased from the UE's database.
Description
BACKGROUND
[0001] 1. Field
[0002] The present application relates generally to wireless
communications, and more specifically to method and system for
storing information to locate a femto cell.
[0003] 2. Background
[0004] Wireless communication systems are widely deployed to
provide various types of communication (e.g., voice, data,
multimedia services, etc.) to multiple users. As the demand for
high-rate and multimedia data services rapidly grows, there lies a
challenge to implement efficient and robust communication systems
with enhanced performance.
[0005] In recent years, users have started to replace fixed line
communications with mobile communications and have increasingly
demanded great voice quality, reliable service, and low prices.
[0006] In addition to mobile phone networks currently in place, a
new class of small base stations has emerged, which may be
installed in a user's home and provide indoor wireless coverage to
mobile units using existing broadband Internet connections. Such
personal miniature base stations are generally known as access
point base stations, or, alternatively, Home Node B (HNB), or Femto
cells. Typically, such miniature base stations are connected to the
Internet and the mobile operator's network via DSL router or cable
modem or other backhaul technologies.
[0007] One of the issues with mobile stations and femto cells is
how to find a femto cell when it is operating on a macro-cellular
network. The mobile station may be on a frequency different than
one used by the femto cell. Alternatively, the femto cell may reuse
one of several available carrier frequencies. If the mobile is not
on that very frequency, it would miss the femto cell, and continue
to operate on the macro cell, although it is within the coverage of
the femto cell. Additionally, even if there is a way to find a
femto cell, mobile may not be authorized to access it (access may
be restricted). The problem can be further complicated by the fact
that new femto cells are put in operation all the time.
[0008] Currently proposed solutions use pilot beacons to signal on
other frequencies the presence of the femto cell on the frequency
used by femtos. This approach has a weakness because it adds to
interference on the other frequencies. Other proposals include
constant periodic search for femto cells, which can hurt battery
life. Accordingly, there is a need in the art for mobile devices to
be able to determine where to search for a femto cell.
SUMMARY
[0009] The preferred embodiment relates to as a system and a method
for storing information to locate a femto cell that substantially
eliminates one or several disadvantages of the related art.
[0010] In one aspect of the preferred embodiment there is a system,
method and computer product for augmenting a user's equipment (UE)
database with information measured by a femto cell, the method
comprising: (a) performing RF measurements by a femto cell to
determine a location of the femto cell; (b) connecting the UE to
the femto cell; (c) downloading the RF measurements taken by the
femto cell pertaining to the location of the femto cell into the UE
database.
[0011] The method further comprising: (a) taking RF measurements by
the UE; (b) comparing current RF measurements taken by the UE with
the femto cell own RF measurements to estimate proximity to the
femto cell.
[0012] Obviously, this requires a protocol to communicate this
information between the femto cell and the UE. A simple alternative
to a new communication protocol would be for the UE to store the RF
measurements to neighboring macro cell at the time when it receives
the strongest signal from the associated femto cell.
[0013] In other aspects of the preferred embodiment there is a
system, method and computer product for augmenting a user's
equipment (UE) database with information processed at a back-end
server based on a multiple UE reports from the multiple UEs for
locating femto cells, the back-end server is part of a macro cell
network, the method comprising: (a) performing RF measurements by a
plurality of UE, wherein RF measurements determine a location of a
femto cell based on the UE's location relative to at least one
macro cell; (b) sending the location information to the back-end
server; (c) processing at the back-end server the locations to
average location for the femto cell; (d) connecting the UE to the
back-end server; (e) downloading the average location for the femto
cell into the UE's database.
[0014] In one embodiment, it does not require an over-the-air
protocol to communicate this information between the back-end
server and the UE. For this embodiment, an application is used,
running over the existing internet protocols (e.g., TCP/IP) used
normally by the femto cell.
[0015] In other aspects of the preferred embodiment there is a
system, method and computer product for augmenting a user's
equipment (UE) database with information pertaining to changes in
macro environment, the method comprising: (a) storing by the UE RF
measurements to neighboring macro cells at the time when the UE
receives the strongest signal from a femto cell; (b) performing by
the UE RF measurements pertaining to a macro cell phase off; (c)
downloading into the UE database the information pertaining to
changes in macro cell environment.
[0016] The information about previously stored macro cells may
remain in the UE database depending on the strength of the
pilots.
[0017] Additional features and advantages of the invention will be
set forth in the description that follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The advantages of the invention will be realized and
attained by the structure particularly pointed out in the written
description and claims hereof as well as the appended drawings.
[0018] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a exemplary wireless communication system;
[0020] FIG. 2 is a an exemplary communication system to enable
deployment of access point base stations within a network
environment;
[0021] FIG. 3 illustrates a method augmenting a user's equipment
(UE) database with information measured by a femto cell.
[0022] FIG. 4 illustrates refinement of autonomous and customized
discovery of femto cells.
[0023] FIG. 5 illustrates a pilot phase planning chart.
[0024] FIG. 6 illustrates a system used for augmenting a user's
equipment (UE) database with information processed at a back-end
server based on reports from multiple UEs.
[0025] FIG. 7A is a method for augmenting a user's equipment (UE)
database with information processed at a back-end server based on
reports from multiple UEs.
[0026] FIG. 7B illustrates a simplified block diagram of several
sample aspects of communication components.
[0027] FIG. 8 is an alternate method for augmenting a user's
equipment (UE) database.
[0028] FIG. 9 depicts an example block diagram of a system 800 in
accordance with additional aspects described herein.
DETAILED DESCRIPTION
[0029] The word "exemplary" is used herein to mean "serving as an
example, instance, or illustration." Any embodiment described
herein as "exemplary" is not necessarily to be construed as
preferred or advantageous over other embodiments. The techniques
described herein may be used for various wireless communication
networks such as Code Division Multiple Access (CDMA) networks,
Time Division Multiple Access (TDMA) networks, Frequency Division
Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks,
Single-Carrier FDMA (SC-FDMA) networks, etc. The terms "networks"
and "systems" are often used interchangeably. A CDMA network may
implement a radio technology such as Universal Terrestrial Radio
Access (UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA)
and Low Chip Rate (LCR). cdma2000 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). Long Term Evolution (LTE) is an upcoming release of
UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are
described in documents from an organization named "3rd Generation
Partnership Project" (3GPP). cdma2000 is described in documents
from an organization named "3rd Generation Partnership Project 2"
(3GPP2). These various radio technologies and standards are known
in the art.
[0030] In the description herein, a node that provides coverage
over a relatively large area may be referred to as a macro node
while a node that provides coverage over a relatively small area
(e.g., a residence) may be referred to as a femto node. It should
be appreciated that the teachings herein may be applicable to nodes
associated with other types of coverage areas. For example, a pico
node may provide coverage over an area that is smaller than a macro
area and larger than a femto area (e.g., coverage within a
commercial building). In various applications, other terminology
may be used to reference a macro node, a femto node, or other
access point-type nodes. For example, a macro node may be
configured or referred to as an access node, base station, access
point, eNodeB, macro cell, and so on. Also, a femto node may be
configured or referred to as a Home NodeB, Home eNodeB, access
point base station, femto cell, and so on. In some implementations,
a node may be associated with (e.g., divided into) one or more
cells or sectors. A cell or sector 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. A simplified example of
how femto nodes may be deployed in a network will now be described
with reference to FIGS. 1 and 2.
[0031] FIG. 1 illustrates an exemplary wireless communication
system 100 configured to support a number of users, in which
various disclosed embodiments and aspects may be implemented. As
shown in FIG. 1, by way of example, 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 point (AP) or points 104, such as, for example, APs
104a-104g. Each macro cell may be further divided into one or more
sectors (not shown). As further shown in FIG. 1, various access
terminal (AT) devices 106, including ATs 106a-1061, also known
interchangeably as user equipment (UE), or as mobile stations (MS),
or as terminal devices, may be dispersed at various locations
throughout the system. Each AT 106 may communicate with one or more
APs 104 on a forward link (FL) and/or a reverse link (RL) at a
given moment, depending upon whether the AT 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 only a few blocks within a
neighborhood or several square miles in a rural environment.
[0032] FIG. 2 illustrates an exemplary communication system to
enable deployment of femto nodes, also known as femto cells (access
point base stations) within a network environment. As shown in FIG.
2, the system 200 includes multiple femto nodes, or, in the
alternative, femto cells, access point base stations, Home Node B
(HNB) units such as, for example, HNB 210, 215, each being
installed in a corresponding relatively small coverage network
environment, such as, for example, in one or more sites 230, and
such as, for example, being configured to serve associated user
equipment 220. Each HNB 210 may be coupled to and further
configured to communicate via a wide area network, such as the
Internet 240, and to any node on the Internet, including a macro
mobile operator core network 250 (also referred to as a "core
network"). As shown, there are at least two communication paths
between a terminal device 220 and the macro mobile operator core
network 250, namely a path including macro cell access, and a path
including the Internet 240.
[0033] Although embodiments described herein use 3GPP terminology,
it is to be understood that the embodiments may be applied to 3GPP
(Re199, Re15, Re16, Re17) technology, as well as 3GPP2 (1xRTT,
1xEV-DO Re10, RevA, RevB) technology, WiMax and other known and
related technologies. In such embodiments described herein, the
owner of the HNB 210 and the HNB 215 subscribes to mobile service,
such as, for example, a 3G mobile service, offered through the
mobile operator core network 250, and the UE 220 is capable to
operate both in macro cellular environment and in residential small
scale network environment. Thus, the HNB 210 and the HNB 215 are
backward compatible with any existing UE 220.
[0034] Furthermore, in addition to the macro cell mobile network
250, the UE 220 can be served by a limited number of HNBs 210, e.g.
a HNB 210 located within the user residence 230. For example the UE
220 may be served by the HNB 210, while it does not have access to
HNB 215.
[0035] One of the issues with UEs and HNBs or femto cells is how to
find a femto cell 210 when it is operating on a macro-cellular
network 250. The UE 220 may be operating on a frequency different
than the one used by the femto cell 210. In the course of searching
procedures, where the UE 220 evaluates a neighbor list from the
macro cells, it will not find the femto cell 210. Femto cells may
use one of several available carrier frequencies. If the UE 220 is
not operating on that very frequency, it would miss the femto cell
210, and continue to operate on the macro cell, although it is
within coverage of the femto cell 210. Additionally, even if there
is a way to find a femto cell 215, the UE 220 may not be authorized
to access it (access may be restricted). The problem can be further
complicated by the fact that new femto cells are put in operation
all the time. The key advantages of the invention include: improved
battery performance largely autonomous operation and automatic
provisioning of the UEs, without requiring network downloads.
[0036] According to embodiments described in detail below, the UE
220 acquires (by learning or otherwise) a database of HNBs or femto
cells 210 individualized for that UE 220. The database is stored on
the UE 220, and may include for each femto cell 210 the following
information: --Carrier frequency--Location (latitude/longitude
(LAT/LON), or an alternative)--List of CDMA Pilots and phase
offsets in vicinity of the Hot Spot, with E.sub.C/Io above a given
threshold--Date femto access was last used/acquired by this access
terminal or UE 220--Other identification information, such as
System ID for the femto cell, Network ID for the femto cell, and
Radio Technology used by the femto cell.
[0037] In one embodiment, each entry of the database describes a
femto cell location in a non-orthogonal coordinate system comprised
of macro pilots visible at that femto location (with qualifying
minimum E.sub.C/Io), the phase delay of each pilot, and allowed
deviation around that nominal phase delay. When the database is
already available in the UE 220, it can be used to reduce femto
searching, (i.e., conduct femto search only if there is a match in
the database). The UE 220 on a frequency other than FF conducts
search on FF only when there is a database match. In one
embodiment, the database elements include macro pilot PN offsets,
which are all visible by the UE 220 on whatever carrier it is
monitoring in the idle state. These PN offsets are accessible to
the UE in the course of routine operation in idle state, and the UE
does not have to do anything different until there is a database
match. Then, the UE 220 starts scanning for the HNB or femto cell
210, which is on a different frequency. Operating this way will
reduce battery drainage.
[0038] FIG. 3 illustrates a method augmenting a user's equipment
(UE) database with information measured by a femto cell. The femto
cell 210 will typically have a radio that receives the Macro
channels, in order to facilitate various configuration objectives
like synchronization, location, pilot PN planning, etc.
Consequently, since the Femto 210 in addition to its forward link
transmitter, also has a forward link receiver, it itself could
measure its RF environment within neighboring Macro cells. Advanced
antenna configurations have interference reduction. Furthermore,
this measurement is likely to be quite accurate since the Femto 210
is stationary, and can average the measurements over a long period
of time. The Femto 210 can spend a lot of time searching for pilots
of neighboring macro cells, integrating CDMA signals from very weak
pilots. The Femto 210 performs its own measurements in Step
302.
[0039] In Step 304, the UE 220 connects to the Femto 210 for the
first time. The Femto 210 downloads its measurements or parameters
to the UE database in Step 306 to determine location of the femto
cell. When the next time the UE 220 approaches the Femto 210 as
shown in Step 308, it can compare its current measurements with the
Femto's own readings to estimate its proximity to the Femto 210 as
shown in Step 310.
[0040] This has a further advantage that if the UE 220 approaches
the Femto 210 again (for the third time) from a different direction
than the second time as shown in Step 312, then the error in
measurement will be minimized, if the comparison point is at the
Femto 210 itself, which makes this system more robust.
[0041] FIG. 4 illustrates refinement of autonomous and customized
discovery of femto cells. The location of a femto cell may be
described by means of primitives comprised of macro system
parameters: within the area described by base station (BS) set C,
in which Pilots exceed threshold E.sub.C/Io vector D, and have
phase P within tolerance Q. All these parameters may be measured
with little or no change of CDMA procedure (idle or active state),
hence they will have minimal cost in terms of battery life and/or
network use, in contrast to e.g. A-GPS geo-location.
[0042] FIG. 5 illustrates pilot phase planning chart. The chart
shows that femto cells can be very dense. MP.sub.0 through MP.sub.7
are PN Offsets for macro cells and fP.sub.1 and fP.sub.2 are phase
offsets for femto cells. In the long-term, there may be as many
femto PN Offsets as for macro cells. This can be achieved in a
couple of ways: (1) decrement PILOT_INC, thus creating an
odd-numbered PN Offsets for femto cells; and (2) re-program macro
macro cellular network by re-assigning odd PN offsets to even
ones.
[0043] For example, 2.pi./128*2i result in 64 macro PN Offsets
(even numbered) and 2.pi./128*(2i+1) result in 64 femto PN Offsets
(odd numbered PN Offsets). Initially, at low density of femtos, a
subset of PN Offsets can be used for femtos (explicitly in neighbor
list). By the time femto density gets high, new femto-aware MS will
have been fielded and can deal with the entire set of femto PN
offsets.
[0044] In one embodiment, an over-the-air protocol is required to
communicate this information between the Femto 210 and the UE 220.
A simple alternative to a new communication protocol would be for
the UE 220 to store the RF measurements to neighboring macro cells
at the time when it receives the strongest signal from the
associated femto cell. Since the strongest signal is likely to
correspond to the closest location, this minimizes the error in the
UE's database entry. This entry may be re-written every time the UE
samples a stronger signal from the Femto.
[0045] Finally, this measurement at the Femto cell 210 can be used
to trigger some error conditions at an UE, if there is a wide
divergence in the measurements reported by an associated UE, and
those made at the Femto.
[0046] Another alternative to a new communication protocol is when
the information is processed at a back-end server based on the
multiple UE reports. FIG. 6 illustrates a system used for
augmenting a user's equipment (UE) database with information
processed at a back-end server based on a multiple UE reports. A
plurality of the UEs' 220 performs RF measurements relative to a
location of a femto cell. The back-end server 610 is a part of the
micro cell mobile network 250. The UEs' 220 send the UEs'
measurements pertaining to the location of the femto cell to the
back-end sever 610. The back-end sever 610 processes these
locations to average the location for the femto cell. The sever 610
downloads the processed average location for the femto cell into
the database of the UE 220 by using an application on the UE 220
that communicates with the back-end server over the Internet. The
server 610 stays connected to the Internet 240.
[0047] FIG. 7A is a flow diagram illustrating a method for
augmenting a user's equipment (UE) database with information
processed at a back-end server based on a UE report from multiple
UEs' for locating a femto cells. The back-end server 610 is a part
of the micro cell mobile network 250. In Step 702 a plurality of
UEs' 220 perform RF measurements related to a location of a femto
cell. In Step 704 the UEs' 220 send these measurements pertaining
to the location of the femto cell to the back-end server 610. In
Step 706 the server 610 processes these locations to average the
location for the femto cell. In Step 708 connecting the UE 220 to
the back-end server 610. In Step 709 the back-end server 610
downloads the average location for the femto cell into the UE 220
database.
[0048] In one embodiment, this does not require any new
over-the-air protocol to communicate this information between the
back-end server and the UE. For this embodiment, an application is
used, running over the existing internet protocols (e.g., TCP/IP)
used normally by the femto cell 210.
[0049] It should be appreciated that the teachings herein may be
implemented in various types of communication devices. In some
aspects, the teachings herein may be implemented in wireless
devices that may be deployed in multiple access communication
system that may simultaneously support communication for multiple
wireless access terminals. Here, each terminal may communicate with
one or more access points via transmissions on the forward and
reverse links. The forward link (or downlink) refers to the
communication link from the access points to the terminals, and the
reverse link (or uplink) refers to the communication link from the
terminals to the access points. This communication link may be
established via a single-in-single-out system, a
multiple-in-multiple-out ("MIMO") system, or some other type of
system.
[0050] A MIMO system employs multiple (N.sub.T) transmit antennas
and multiple (N.sub.R) receive antennas 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.ltoreq.min
{N.sub.T, N.sub.R}. Each of the Ns 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.
[0051] A MIMO system 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 the access
point to extract transmit beam-forming gain on the forward link
when multiple antennas are available at the access point.
[0052] The teachings herein may be incorporated into a node (e.g.,
a device) employing various components for communicating with at
least one other node. FIG. 7B depicts several sample components
that may be employed to facilitate communication between nodes.
Specifically, FIG. 7B illustrates a wireless device 710 (e.g., an
access point) and a wireless device 750 (e.g., an access terminal)
of a MIMO system 700. At the device 710, traffic data for a number
of data streams is provided from a data source 712 to a transmit
("TX") data processor 714.
[0053] In some aspects, each data stream is transmitted over a
respective transmit antenna. The TX data processor 714 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.
[0054] 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 730. A data memory 732 may store program
code, data, and other information used by the processor 730 or
other components of the device 710.
[0055] The modulation symbols for all data streams are then
provided to a TX MIMO processor 720, which may further process the
modulation symbols (e.g., for OFDM). The TX MIMO processor 720 then
provides N.sub.T modulation symbol streams to N.sub.T transceivers
("XCVR") 722A through 722T. In some aspects, the TX MIMO processor
720 applies beam-forming weights to the symbols of the data streams
and to the antenna from which the symbol is being transmitted.
[0056] Each transceiver 722 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
722A through 722T are then transmitted from N.sub.T antennas 724A
through 724T, respectively.
[0057] At the device 750, the transmitted modulated signals are
received by N.sub.R antennas 752A through 752R and the received
signal from each antenna 752 is provided to a respective
transceiver ("XCVR") 754A through 754R. Each transceiver 754
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.
[0058] A receive ("RX") data processor 760 then receives and
processes the N.sub.R received symbol streams from N.sub.R
transceivers 754 based on a particular receiver processing
technique to provide N.sub.T "detected" symbol streams. The RX data
processor 760 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 760 is
complementary to that performed by the TX MIMO processor 720 and
the TX data processor 714 at the device 710.
[0059] A processor 770 periodically determines which pre-coding
matrix to use (discussed below). The processor 770 formulates a
reverse link message comprising a matrix index portion and a rank
value portion. A data memory 772 may store program code, data, and
other information used by the processor 770 or other components of
the device 750.
[0060] 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 738, which also receives traffic data for a number
of data streams from a data source 736, modulated by a modulator
780, conditioned by the transceivers 754A through 754R, and
transmitted back to the device 710.
[0061] At the device 710, the modulated signals from the device 750
are received by the antennas 724, conditioned by the transceivers
722, demodulated by a demodulator ("DEMOD") 740, and processed by a
RX data processor 742 to extract the reverse link message
transmitted by the device 750. The processor 730 then determines
which pre-coding matrix to use for determining the beam-forming
weights then processes the extracted message.
[0062] 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. 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, TDSCDMA, 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.degree., etc. UTRA, E-UTRA, and GSM are part of
Universal Mobile Telecommunication System ("UMTS"). The teachings
herein may be implemented in a 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 (Re199, Re15, Re16, Re17) technology, as well as
3GPP2 (IxRTT, 1xEV-DO RelO, RevA, RevB) technology and other
technologies.
[0063] The teachings herein may be incorporated into (e.g.,
implemented within or performed by) a variety of apparatuses (e.g.,
nodes). In some aspects, a node (e.g., a wireless node) implemented
in accordance with the teachings herein may comprise an access
point or an access terminal.
[0064] For example, an access terminal may comprise, be implemented
as, or known as user equipment, a subscriber station, a subscriber
unit, a mobile station, a mobile, a mobile node, a remote station,
a remote terminal, a user terminal, a user agent, a user device, or
some other terminology. In some implementations an access terminal
may comprise a cellular telephone, a cordless telephone, a session
initiation protocol ("SIP") phone, a wireless local loop ("WLL")
station, a personal digital assistant ("PDA"), a handheld device
having wireless connection capability, or some other suitable
processing device connected to a wireless modem. Accordingly, one
or more aspects taught herein may be incorporated into a phone
(e.g., a cellular phone or smart phone), a computer (e.g., a
laptop), a portable communication device, a portable computing
device (e.g., a personal data assistant), an entertainment device
(e.g., a music device, a video device, or a satellite radio), a
global positioning system device, or any other suitable device that
is configured to communicate via a wireless medium.
[0065] An access point may comprise, be implemented as, or known as
a NodeB, an eNodeB, a radio network controller ("RNC"), a base
station ("BS"), a radio base station ("RBS"), a base station
controller ("BSC"), a base transceiver station ("BTS"), a
transceiver function ("TF"), a radio transceiver, a radio router, a
basic service set ("BSS"), an extended service set ("ESS"), or some
other similar terminology.
[0066] In some aspects a node (e.g., an access point) may comprise
an access node for a communication system. Such an access node may
provide, for example, connectivity for or to a network (e.g., a
wide area network such as the Internet or a cellular network) via a
wired or wireless communication link to the network.
[0067] Accordingly, an access node may enable another node (e.g.,
an access terminal) to access a network or some other
functionality. In addition, it should be appreciated that one or
both of the nodes may be portable or, in some cases, relatively
non-portable.
[0068] Also, it should be appreciated that a wireless node may be
capable of transmitting and/or receiving information in a
non-wireless manner (e.g., via a wired connection). Thus, a
receiver and a transmitter as discussed herein may include
appropriate communication interface components (e.g., electrical or
optical interface components) to communicate via a non-wireless
medium.
[0069] A wireless node may communicate via one or more wireless
communication links that are based on or otherwise support any
suitable wireless communication technology. For example, in some
aspects a wireless node may associate with a network. In some
aspects the network may comprise a local area network or a wide
area network. A wireless device may support or otherwise use one or
more of a variety of wireless communication technologies,
protocols, or standards such as those discussed herein (e.g., CDMA,
TDMA, OFDM, OFDMA, WiMAX, Wi-Fi, and so on). Similarly, a wireless
node may support or otherwise use one or more of a variety of
corresponding modulation or multiplexing schemes. A wireless node
may thus include appropriate components (e.g., air interfaces) to
establish and communicate via one or more wireless communication
links using the above or other wireless communication
technologies.
[0070] For example, a wireless node may comprise a wireless
transceiver with associated transmitter and receiver components
that may include various components (e.g., signal generators and
signal processors) that facilitate communication over a wireless
medium.
[0071] The embodiment below describes another method of augmenting
a UE's data base. FIG. 8 illustrates a method of augmenting the UE
220 database based on changes in micro cell environment 250. In
Step 802 the UE 220 stores a femto cell's RF measurements to
neighboring macro cells at the time when the UE 220 receives the
strongest signal. In Step 804 the UE 220 performs RF measurements
pertaining to a macro cell phase offsets. In Step 806 the UE 220
data base gets downloaded with the information related to changes
in macro cellular environment. The information in the UE 220
database gets updated every time the UE 220 samples a stronger
signal from the femto cell. Finally, the RF measurements at the
femto cell may be used to trigger an error conditions at the UE
220, if there is a wide divergence in the measurements reported by
an associated UE, and those made the femto cell.
[0072] FIG. 9 depicts an example block diagram of a system 900 in
accordance with additional aspects described herein. System 900
provides an apparatus that can facilitate locating a femto cell.
Specifically, system 900 can include a plurality of modules or
means, such as, for example, performing means 910, connecting means
920, downloading means 930, sending or transmitting means 940,
processing means 950, and storing means 960, each connected to a
communication link 905, and can communicate with other modules or
means over communication link 905.
[0073] Those of skill in the art would understand that information
and signals may be represented using any of a variety of different
technologies and techniques. For example, data, instructions,
commands, information, signals, bits, symbols, and chips that may
be referenced throughout the above description may be represented
by voltages, currents, electromagnetic waves, magnetic fields or
particles, optical fields or particles, or any combination
thereof.
[0074] Those of skill would further appreciate that the various
illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the embodiments disclosed herein may
be implemented as electronic hardware, computer software, or
combinations of both. To clearly illustrate this interchangeability
of hardware and software, various illustrative components, blocks,
modules, circuits, and steps have been described above generally in
terms of their functionality. Whether such functionality is
implemented as hardware or software depends upon the particular
application and design constraints imposed on the overall system.
Skilled artisans may implement the described functionality in
varying ways for each particular application, but such
implementation decisions should not be interpreted as causing a
departure from the scope of the present invention.
[0075] The various illustrative logical blocks, modules, and
circuits described in connection with the embodiments disclosed
herein may be implemented or performed with a general purpose
processor, a digital signal processor (DSP), an application
specific integrated circuit (ASIC), a field programmable gate array
(FPGA) or other programmable logic device, discrete gate or
transistor logic, discrete hardware components, or any combination
thereof designed to perform the functions described herein. A
general purpose processor may be a microprocessor, but in the
alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also
be implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0076] The steps of a method or algorithm described in connection
with the embodiments disclosed herein may be embodied directly in
hardware, in a software module executed by a processor, or in a
combination of the two. A software module may reside in RAM memory,
flash memory, ROM memory, EPROM memory, EEPROM memory, registers,
hard disk, a removable disk, a CD-ROM, or any other form of storage
medium known in the art. An exemplary storage medium is coupled to
the processor such the processor can read information from, and
write information to, the storage medium. In the alternative, the
storage medium may be integral to the processor. The processor and
the storage medium may reside in an ASIC. The ASIC may reside in a
user terminal. In the alternative, the processor and the storage
medium may reside as discrete components in a user terminal.
[0077] The previous description of the disclosed embodiments is
provided to enable any person skilled in the art to make or use the
present invention. Various modifications to these embodiments will
be readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other embodiments
without departing from the spirit or scope of the invention. Thus,
the present invention is not intended to be limited to the
embodiments shown herein but is to be accorded the widest scope
consistent with the principles and novel features disclosed
herein.
* * * * *