U.S. patent application number 12/048913 was filed with the patent office on 2008-09-18 for handover in wireless communications.
This patent application is currently assigned to QUALCOMM Incorporated. Invention is credited to Etienne F. Chaponniere, Aleksandar Damnjanovic, Durga Prasad Malladi.
Application Number | 20080225796 12/048913 |
Document ID | / |
Family ID | 39762576 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080225796 |
Kind Code |
A1 |
Malladi; Durga Prasad ; et
al. |
September 18, 2008 |
HANDOVER IN WIRELESS COMMUNICATIONS
Abstract
Systems and methodologies are described that facilitate handing
over mobile device communications in a wireless network from a
source base station to a target base station without using a random
access channel (RACH). In this regard, the mobile device can
monitor multiple base stations determining timing information
related thereto and access scheduling request channels for the base
stations. When ready for handover, the mobile device can request
data resources over the scheduling request channel using the
appropriate timing information.
Inventors: |
Malladi; Durga Prasad; (San
Diego, CA) ; Damnjanovic; Aleksandar; (Del Mar,
CA) ; Chaponniere; Etienne F.; (Rome, IT) |
Correspondence
Address: |
QUALCOMM INCORPORATED
5775 MOREHOUSE DR.
SAN DIEGO
CA
92121
US
|
Assignee: |
QUALCOMM Incorporated
San Diego
CA
|
Family ID: |
39762576 |
Appl. No.: |
12/048913 |
Filed: |
March 14, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60895449 |
Mar 17, 2007 |
|
|
|
Current U.S.
Class: |
370/331 |
Current CPC
Class: |
H04W 72/1284 20130101;
H04L 5/0048 20130101; H04W 56/0045 20130101; H04W 36/08
20130101 |
Class at
Publication: |
370/331 |
International
Class: |
H04Q 7/00 20060101
H04Q007/00 |
Claims
1. A method for handing over communications in a wireless network,
comprising: receiving wireless communications service from a source
base station; receiving multiple assigned uplink control channels
for transmitting schedule request signals to a plurality of target
base stations; and transmitting a scheduling request to a selected
target base station of the plurality of target base stations over
at least one of the assigned uplink control channels.
2. The method of claim 1, further comprising receiving timing
advance (TA) information from the plurality of target base
stations, the TA information is utilized to transmit the scheduling
request.
3. The method of claim 2, the TA information is received in
response to sounding reference signals sent to the plurality of
target base stations.
4. The method of claim 2, the TA information is derived from
additional channels of the plurality of base stations in an
asynchronous wireless communications network.
5. The method of claim 2, further comprising maintaining
synchronization with the one or more assigned uplink control
channels, using the trimming advance, to facilitate subsequent
handing over of communication to the selected target base
station.
6. The method of claim 5, the scheduling request transmitted to the
selected target base station based at least in part on a small
timing difference between the target base station and the source
base station as compared to the other target base stations.
7. The method of claim 1, the source base station and the target
base station are synchronized in time, the timing for the source
base station is utilized to transmit the scheduling request.
8. The method of claim 1, further comprising selecting a
transmission time interval (TTI) having a longer cyclic prefix with
respect to the selected target base station for transmitting the
handover communication.
9. The method of claim 1, further comprising receiving wireless
communication service from the selected target base station
following transmitting the initial handover communication.
10. A wireless communications apparatus, comprising: at least one
processor configured to: monitor timing of a plurality of base
stations; and select a target base station in the plurality of base
stations for handover of communications based at least in part on
the monitored timing; and a memory coupled to the at least one
processor.
11. The wireless communications apparatus of claim 10, the timing
is monitored based at least in part on transmitting sounding
reference signals to the base stations.
12. The wireless communications apparatus of claim 11, a timing
advance for the base stations is received in reference to the
sounding reference signals.
13. The wireless communications apparatus of claim 12, the at least
one processor further configured to transmit an initial handover
message to the target base station based at least in part on the
timing advance.
14. The wireless communications apparatus of claim 13, the at least
one processor further configured to select a transmission time
interval (TTI) having a longer cyclic prefix with respect to the
target base station for transmitting the initial handover
message.
15. The wireless communications apparatus of claim 10, the at least
one processor further configured to establish an uplink schedule
request channel with the plurality of base stations, the
established uplink schedule request channel is utilized to handover
communications.
16. The wireless communications apparatus of claim 10, the at least
one processor further configured to determine a timing advance for
the base stations based at least in part on a difference between
timing of the target base station and a source base station in a
wireless communications network.
17. The wireless communications apparatus of claim 10, the
monitoring of the uplink scheduling resources is performed during
communications gaps requested from a source base station to which
the wireless communications apparatus is currently
communicating.
18. A wireless communications apparatus for handing over
communications in a wireless network, comprising: means for
receiving wireless communications service from a source base
station; means for receiving multiple assigned uplink control
channels for transmitting schedule request signals to a plurality
of target base stations; and means for transmitting a scheduling
request to a selected target base station of the plurality of
target base stations over at least one of the assigned uplink
control channels.
19. The wireless communications apparatus of claim 18, further
comprising means for receiving timing advance (TA) information from
the plurality of target base stations, the TA information is
utilized to transmit the scheduling request.
20. The wireless communications apparatus of claim 19, the TA
information is received in response to sounding reference signals
sent to the plurality of target base stations.
21. The wireless communications apparatus of claim 19, the TA
information is derived from additional channels of the plurality of
base stations in an asynchronous wireless communications
network.
22. The wireless communications apparatus of claim 19, further
comprising means for maintaining synchronization with the one or
more assigned uplink control channels, using the trimming advance,
to facilitate subsequent handing over of communication to the
selected target base station.
23. The wireless communications apparatus of claim 22, the
scheduling request transmitted to the selected target base station
based at least in part on a small timing difference between the
target base station and the source base station as compared to the
other target base stations.
24. The wireless communications apparatus of claim 18, the source
base station and the target base station are synchronized in time,
the timing for the source base station is utilized to transmit the
scheduling request.
25. The wireless communications apparatus of claim 18, further
comprising selecting a transmission time interval (TTI) having a
longer cyclic prefix with respect to the selected target base
station for transmitting the handover communication.
26. The wireless communications apparatus of claim 18, further
comprising receiving wireless communication service from the
selected target base station following transmitting the initial
handover communication.
27. A computer program product, comprising: a computer-readable
medium comprising: code for causing at least one computer to
receive wireless communications service from a source base station;
code for causing the at least one computer to receive multiple
assigned uplink control channels for transmitting schedule request
signals to a plurality of target base stations; and code for
causing the at least one computer to transmit a scheduling request
to a selected target base station of the plurality of target base
stations over at least one of the assigned uplink control channels.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent application Ser. No. 60/895,449 entitled "OPTIMIZED FORWARD
HANDOVER PROCEDURE FOR LTE" which was filed Mar. 17, 2007. The
entirety of the aforementioned application is herein incorporated
by reference.
BACKGROUND
[0002] I. Field
[0003] The following description relates generally to wireless
communications, and more particularly to handover in wireless
communications networks.
[0004] II. Background
[0005] Wireless communication systems are widely deployed to
provide various types of communication content such as, for
example, voice, data, and so on. Typical wireless communication
systems may be multiple-access systems capable of supporting
communication with multiple users by sharing available system
resources (e.g., bandwidth, transmit power, . . . ). Examples of
such multiple-access systems may include code division multiple
access (CDMA) systems, time division multiple access (TDMA)
systems, frequency division multiple access (FDMA) systems,
orthogonal frequency division multiple access (OFDMA) systems, and
the like. Additionally, the systems can conform to specifications
such as third generation partnership project (3GPP), 3GPP long term
evolution (LTE), etc.
[0006] Generally, wireless multiple-access communication systems
may simultaneously support communication for multiple mobile
devices. Each mobile device may communicate with one or more base
stations via transmissions on forward and reverse links. The
forward link (or downlink) refers to the communication link from
base stations to mobile devices, and the reverse link (or uplink)
refers to the communication link from mobile devices to base
stations. Further, communications between mobile devices and base
stations may be established via single-input single-output (SISO)
systems, multiple-input single-output (MISO) systems,
multiple-input multiple-output (MIMO) systems, and so forth. In
addition, mobile devices can communicate with other mobile devices
(and/or base stations with other base stations) in peer-to-peer
wireless network configurations.
[0007] MIMO systems commonly employ multiple (N.sub.T) transmit
antennas and multiple (N.sub.R) receive antennas for data
transmission. The antennae can relate to both base stations and
mobile devices, in one example, allowing bi-directional
communication between the devices on the wireless network. As
mobile devices move throughout service areas, communication for the
devices can be handed over between one or more base stations. For
example, where an available base station can offer a better signal
or service than a base station currently communicating with the
mobile device, the device can be handed over to the available base
station. This is typically accomplished by using a random access
channel (RACH) to request and schedule resources; however, the RACH
can become over-utilized in active communications networks.
SUMMARY
[0008] The following presents a simplified summary of one or more
embodiments in order to provide a basic understanding of such
embodiments. This summary is not an extensive overview of all
contemplated embodiments, and is intended to neither identify key
or critical elements of all embodiments nor delineate the scope of
any or all embodiments. Its sole purpose is to present some
concepts of one or more embodiments in a simplified form as a
prelude to the more detailed description that is presented
later.
[0009] In accordance with one or more embodiments and corresponding
disclosure thereof, various aspects are described in connection
with facilitating handing-over communications in a wireless
communications network at least in part by requesting or otherwise
obtaining information from one or more target access points, such
as a scheduling request channel, cell radio network temporary
identifier (C-RNTI), channel quality indicator (CQI) resources,
and/or the like. Using the resources, an access terminal can find a
desirable access point for handing-over communications and perform
the handover when advantageous to do so. Additionally, the access
terminal can receive indication of a timing advance (TA) or other
synchronization information regarding the access points to allow
the access terminal to handover without using a random access
channel (RACH).
[0010] According to related aspects, a method for handing over
communications in a wireless network is provided. The method can
include receiving wireless communications service from a source
base station and receiving multiple assigned uplink control
channels for transmitting schedule request signals to a plurality
of target base stations. The method can further include
transmitting a scheduling request to a selected target base station
of the plurality of target base stations over at least one of the
assigned uplink control channels.
[0011] Another aspect relates to a wireless communications
apparatus. The wireless communications apparatus can include at
least one processor configured to monitor timing of a plurality of
base stations and select a target base station in the plurality of
base stations for handover of communications based at least in part
on the monitored timing. The wireless communications apparatus can
also include a memory coupled to the at least one processor.
[0012] Yet another aspect relates to a wireless communications
apparatus for handing over communications in a wireless network.
The wireless communications apparatus can include means for
receiving wireless communications service from a source base
station and means for receiving multiple assigned uplink control
channels for transmitting schedule request signals to a plurality
of target base stations. The wireless communications apparatus can
additionally include means for transmitting a scheduling request to
a selected target base station of the plurality of target base
stations over at least one of the assigned uplink control
channels.
[0013] Still another aspect relates to a computer program product,
which can have a computer-readable medium including code for
causing at least one computer to receive wireless communications
service from a source base station. The computer-readable medium
can further comprise code for causing the at least one computer to
receive multiple assigned uplink control channels for transmitting
schedule request signals to a plurality of target base stations.
Moreover, the computer-readable medium can include code for causing
the at least one computer to scheduling request to a selected
target base station of the plurality of target base stations over
at least one of the assigned uplink control channels.
[0014] To the accomplishment of the foregoing and related ends, the
one or more embodiments comprise the features hereinafter fully
described and particularly pointed out in the claims. The following
description and the annexed drawings set forth in detail certain
illustrative aspects of the one or more embodiments. These aspects
are indicative, however, of but a few of the various ways in which
the principles of various embodiments may be employed and the
described embodiments are intended to include all such aspects and
their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an illustration of a wireless communication system
in accordance with various aspects set forth herein.
[0016] FIG. 2 is an illustration of an example communications
apparatus for employment within a wireless communications
environment.
[0017] FIG. 3 is an illustration of an example wireless
communications system that effectuates handing over communications
using target resources.
[0018] FIG. 4 is an illustration of an example wireless
communications network with mobile devices moving between
sectors.
[0019] FIG. 5 is an illustration of an example methodology that
facilitates requesting handover based on target resources.
[0020] FIG. 6 is an illustration of an example methodology that
facilitates requesting communications gaps from a source base
station.
[0021] FIG. 7 is an illustration of an example mobile device that
facilitates requesting scheduling with a target base station to
facilitate handover.
[0022] FIG. 8 is an illustration of an example system that
facilitates providing resources for handing over
communications.
[0023] FIG. 9 is an illustration of an example wireless network
environment that can be employed in conjunction with the various
systems and methods described herein.
[0024] FIG. 10 is an illustration of an example system that
monitors target communications resources for handing over mobile
device communications.
DETAILED DESCRIPTION
[0025] Various embodiments are now described with reference to the
drawings, wherein like reference numerals are used to refer to like
elements throughout. In the following description, for purposes of
explanation, numerous specific details are set forth in order to
provide a thorough understanding of one or more embodiments. It may
be evident, however, that such embodiment(s) can be practiced
without these specific details. In other instances, well-known
structures and devices are shown in block diagram form in order to
facilitate describing one or more embodiments.
[0026] As used in this application, the terms "component,"
"module," "system," and the like are intended to refer to a
computer-related entity, either hardware, firmware, a combination
of hardware and software, software, or software in execution. For
example, a component can be, but is not limited to being, a process
running on a processor, a processor, an object, an executable, a
thread of execution, a program, and/or a computer. By way of
illustration, both an application running on a computing device and
the computing device can be a component. One or more components can
reside within a process and/or thread of execution and a component
can be localized on one computer and/or distributed between two or
more computers. In addition, these components can execute from
various computer readable media having various data structures
stored thereon. The components can communicate by way of local
and/or remote processes such as in accordance with a signal having
one or more data packets (e.g., data from one component interacting
with another component in a local system, distributed system,
and/or across a network such as the Internet with other systems by
way of the signal).
[0027] Furthermore, various embodiments are described herein in
connection with a mobile device. A mobile device can also be called
a system, subscriber unit, subscriber station, mobile station,
mobile, remote station, remote terminal, access terminal, user
terminal, terminal, wireless communication device, user agent, user
device, or user equipment (UE). A mobile device can be 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, computing device, or other processing device
connected to a wireless modem. Moreover, various embodiments are
described herein in connection with a base station. A base station
can be utilized for communicating with mobile device(s) and can
also be referred to as an access point, Node B, evolved Node B
(eNode B or eNB), base transceiver station (BTS) or some other
terminology.
[0028] Moreover, various aspects or features described herein can
be implemented as a method, apparatus, or article of manufacture
using standard programming and/or engineering techniques. The term
"article of manufacture" as used herein is intended to encompass a
computer program accessible from any computer-readable device,
carrier, or media. For example, computer-readable media can include
but are not limited to magnetic storage devices (e.g., hard disk,
floppy disk, magnetic strips, etc.), optical disks (e.g., compact
disk (CD), digital versatile disk (DVD), etc.), smart cards, and
flash memory devices (e.g., EPROM, card, stick, key drive, etc.).
Additionally, various storage media described herein can represent
one or more devices and/or other machine-readable media for storing
information. The term "machine-readable medium" can include,
without being limited to, wireless channels and various other media
capable of storing, containing, and/or carrying instruction(s)
and/or data.
[0029] The techniques described herein may be used for various
wireless communication systems such as code division multiple
access (CDMA), time division multiple access (TDMA), frequency
division multiple access (FDMA), orthogonal frequency division
multiple access (OFDMA), single carrier frequency domain
multiplexing (SC-FDMA) and other systems. The terms "system" and
"network" are often used interchangeably. A CDMA system may
implement a radio technology such as Universal Terrestrial Radio
Access (UTRA), CDMA2000, etc. UTRA includes Wideband-CDMA (W-CDMA)
and other variants of CDMA. CDMA2000 covers IS-2000, IS-95 and
IS-856 standards. A TDMA system may implement a radio technology
such as Global System for Mobile Communications (GSM). An OFDMA
system may implement a radio technology such as Evolved UTRA
(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE
802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are
part of Universal Mobile Telecommunication System (UMTS). 3GPP Long
Term Evolution (LTE) is an upcoming release of UMTS that uses
E-UTRA, which employs OFDMA on the downlink and SC-FDMA on the
uplink. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents
from an organization named "3rd Generation Partnership Project"
(3GPP). CDMA2000 and UMB are described in documents from an
organization named "3rd Generation Partnership Project 2"
(3GPP2).
[0030] Referring now to FIG. 1, a wireless communication system 100
is illustrated in accordance with various embodiments presented
herein. System 100 comprises a base station 102 that can include
multiple antenna groups. For example, one antenna group can include
antennas 104 and 106, another group can comprise antennas 108 and
110, and an additional group can include antennas 112 and 114. Two
antennas are illustrated for each antenna group; however, more or
fewer antennas can be utilized for each group. Base station 102 can
additionally include a transmitter chain and a receiver chain, each
of which can in turn comprise a plurality of components associated
with signal transmission and reception (e.g. processors,
modulators, multiplexers, demodulators, demultiplexers, antennas,
etc.), as will be appreciated by one skilled in the art.
[0031] Base station 102 can communicate with one or more mobile
devices such as mobile device 116 and mobile device 122; however,
it is to be appreciated that base station 102 can communicate with
substantially any number of mobile devices similar to mobile
devices 116 and 122. Mobile devices 116 and 122 can be, for
example, cellular phones, smart phones, laptops, handheld
communication devices, handheld computing devices, satellite
radios, global positioning systems, PDAs, and/or any other suitable
device for communicating over wireless communication system 100. As
depicted, mobile device 116 is in communication with antennas 112
and 114, where antennas 112 and 114 transmit information to mobile
device 116 over a forward link 118 and receive information from
mobile device 116 over a reverse link 120. Moreover, mobile device
122 is in communication with antennas 104 and 106, where antennas
104 and 106 transmit information to mobile device 122 over a
forward link 124 and receive information from mobile device 122
over a reverse link 126. In a frequency division duplex (FDD)
system, forward link 118 can utilize a different frequency band
than that used by reverse link 120, and forward link 124 can employ
a different frequency band than that employed by reverse link 126,
for example. Further, in a time division duplex (TDD) system,
forward link 118 and reverse link 120 can utilize a common
frequency band and forward link 124 and reverse link 126 can
utilize a common frequency band.
[0032] Each group of antennas and/or the area in which they are
designated to communicate can be referred to as a sector of base
station 102. For example, antenna groups can be designed to
communicate to mobile devices in a sector of the areas covered by
base station 102. In communication over forward links 118 and 124,
the transmitting antennas of base station 102 can utilize
beamforming to improve signal-to-noise ratio of forward links 118
and 124 for mobile devices 116 and 122. Also, while base station
102 utilizes beamforming to transmit to mobile devices 116 and 122
scattered randomly through an associated coverage, mobile devices
in neighboring cells can be subject to less interference as
compared to a base station transmitting through a single antenna to
all its mobile devices. Moreover, mobile devices 116 and 122 can
communicate directly with one another using a peer-to-peer or ad
hoc technology as depicted.
[0033] According to an example, system 100 can be a multiple-input
multiple-output (MIMO) communication system. Further, system 100
can utilize substantially any type of duplexing technique to divide
communication channels (e.g., forward link, reverse link, . . . )
such as FDD, TDD, and the like. The communication channels can
comprise one or more logical channels. Such logical channels can be
provided for transmitting different types of data between the
mobile devices 116 and 122 and the base station 102 (or from mobile
device 116 to mobile device 122 in a peer-to-peer configuration,
for example). Such channels can exist for transmitting control
data, regular shared data (e.g., communication data), random access
data, beacon/pilot data, broadcast data, and/or the like. For
example, the base station 102 can establish a shared data channel
utilized by the mobile devices 116 and 122 to access resources of
the base station; additionally, the base station 102 can have a
dedicated control channel for transmitting control information
related to the shared data channel, for example.
[0034] Communications over the channels can be orthogonal (e.g.,
using OFDM, SC-FDM, and/or the like) such that mobile devices 116
and 122 transmit at different times on a given channel to prevent
collision; to facilitate orthogonal communicating, the mobile
devices 116 and 122 can be given a timing advance (TA) with respect
to transmitting over the channels. The timing advance can specify a
waiting period before the given mobile device can communicate or
the period during which the device is to communicate on the
channel, etc. Additionally, data can be communicated with a cyclic
prefix adjusting for error in timing of transmitting the data. For
example, the cyclic prefix can be a portion of one or more symbols
transmitted on a channel that can be re-transmitted at the
beginning or end of the symbol transmission in the event that a
portion of the symbol is not received due to the timing error. For
given channels, the cyclic prefix can vary to tolerate additional
timing error (this can depend. on the type, demand, and/or method
of connection for the channel, for example). In one example, a
channel utilized to acquire channel resources from a new device can
have a larger cyclic prefix since the timing of the channel is not
certain to the device. In prior systems, the random access channel
(RACH) can have a larger cyclic prefix to allow devices to send
connection or handover requests, for example.
[0035] In one example, the subject matter described herein can
handover devices from one base station to another by allowing the
device being handed over to obtain data resources from the target
base station prior to initiating the handover. In one example, this
can be facilitated by requesting semi-static information from
target base station(s), such as a TA, cell radio network temporary
identifier (C-RNTI), channel quality indicator (CQI) information,
and the like by transmitting a sounding reference signal (SRS)
and/or the like to monitor resources on the target base station(s).
Using this information, the device can determine timing
information, such as a timing advance utilized by the target base
station(s), for handing-over communications to the target base
station(s). Once the device moves within sufficient range of at
least one of the target base station(s), the device can request
data resources from the at least one target base station over a
scheduling request channel using the timing adjustment.
Subsequently, communications can be handed over upon receiving the
data resources. To the extent there is timing error associated with
the data resource request, strategically utilizing transmit time
intervals (TTI) with longer cyclic prefixes (CP) than other TTIs
can help account for the error in one example. Alternatively, in
one example, substantially all CP can be sufficiently long to
account for timing error.
[0036] Turning to FIG. 2, illustrated is a communications apparatus
200 for employment within a wireless communications environment.
The communications apparatus 200 can be a base station or a portion
thereof, a mobile device or a portion thereof, or substantially any
communications apparatus that receives data transmitted in a
wireless communications environment. The communications apparatus
200 can include a target information receiver 202 that can acquire
data regarding disparate communications apparatuses, a target
resource requestor 204 that can request resources from a target
communications apparatus to handover communication from a disparate
device, and a timing adjustor 206 that can correct timing for
communicating with the target communications apparatus.
[0037] According to an example, the target information receiver 202
can receive requested data regarding one or more disparate
communications apparatuses (not shown). For example, the
communications apparatus 200 can be a mobile device and the
disparate communications apparatuses can provide data access to the
mobile device such that the device can be handed over between the
disparate communications apparatuses. The handing over can be based
at least in part on signal quality, services offered by the
apparatuses, and/or the like, for example. The received information
can be related to semi-static information regarding the disparate
communications apparatuses, such as a TA, C-RNTI, CQI information,
etc. and can be received in response to transmitting an SRS to the
apparatuses. The communications apparatus 200 can determine a
better suited communications apparatus for handing-over
communications based at least in part on the information. It is to
be appreciated that the communications apparatus 200 can maintain
and monitor this information with respect to the candidate target
communications apparatuses. In one example, the information can be
received over a downlink control or data channel from the target
communications apparatuses or through the source communications
apparatus. In addition, schedule request channels for the target
communications apparatuses can be assigned to the communications
apparatus 200 by the target communications apparatuses over the air
or through the source communication apparatus (e.g., via backhaul
link).
[0038] Handover of the communications for the communications
apparatus 200 can occur, in one example, where the signal strength
of a target communication apparatus exceeds or is sufficiently
close to that of a source communications apparatus (not shown) to
which the communications apparatus 200 is currently communicating.
When the determination for handing over is made, the communications
apparatus 200 can detect one or more of the target communications
apparatuses having a substantially similar (or a most similar) TA
as the source communications apparatus using the information
received (as described above) and can utilize the target resources
requestor 204 to directly request uplink (UL) resources on the UL
schedule request channel of the target communications apparatus
using the known TA. In this regard, a RACH can be avoided as the
communications apparatus 200 knows the TA from received
information.
[0039] Subsequently, the timing adjustor 206 can be utilized to
make minor adjustments to the timing utilized by the communications
apparatus 200 in communicating with the target communications
apparatus where necessary. In one example, as mentioned, the
communications apparatus 200 can strategically choose to handover
communications to the target communications apparatus in a TTI
where a longer CP can be utilized. For example, the target
communications apparatus can offer such TTIs periodically,
according to a pattern, based on desired handover, and/or the like.
The longer CP can account for initial error; upon receiving a
subsequent communication from the target communications apparatus,
the timing adjustor 206 can synchronize timing with the target
communications apparatus. It is to be appreciated that additional
or alternative mechanisms can be used to account for error in
communication. For example, the communications apparatus 200 can
use a hybrid automatic repeat-request (HARQ) communication for
initially handing over. It is to be appreciated that these
techniques can be most useful where TA is determined based at least
in part on downlink timing difference in an asynchronous wireless
communications network.
[0040] In another example, the communications apparatus 200 can
transmit reference signals to the target communications apparatus
to initially receive information related thereto by the target
information receiver 202. In this regard, the communications
apparatus 200 (or a component thereof which is not shown) can
request communication gaps from the source communications apparatus
where the source communications apparatus can expect not to receive
communications from the communications apparatus 200. During these
gaps, the communications apparatus 200 can send references signals
and/or receive resources from the target communications apparatus
that can subsequently be used in handover as described above.
[0041] Now referring to FIG. 3, illustrated is a wireless
communications system 300 that can utilize target base station
resources for synchronizing data resources in mobile device
handover. The system 300 includes a target base station 302 that
can communicate with a mobile device 304 (and/or any number of
disparate mobile devices (not shown)) to facilitate handing-over
wireless communication service. The mobile device 304 can also be
communicating with a source base station 306 for current wireless
communication service. Base stations 302 and 306 can transmit
information to mobile device 304 over a forward link channel;
further base stations 302 and 306 can receive information from
mobile device 304 over a reverse link or uplink channel. In
addition, the mobile device 304 can desire to handover
communications to the target base station 302 from the source base
station 306 at a particular point in time. Moreover, system 300 can
be a MIMO system. Additionally, the system 300 can operate in an
OFDMA or SC-FDMA wireless network (such as 3GPP, 3GPP LTE, and the
like, for example). Also, the components and functionalities shown
and described below in the base stations 302 and 306 can be present
each other and/or in the mobile device 304 as well and vice versa,
in one example; the configuration depicted excludes these
components for ease of explanation.
[0042] Target base station 302 includes a control resource assignor
308 that can provide control resources to one or more mobile
devices seeking communication handover, a handover request receiver
310 that can obtain a request for handing over communications from
the one or more mobile devices, and a data resource scheduler 312
that can provide data channel access to the one or more mobile
devices to complete the handover procedure. For example, a mobile
device, such as mobile device 304 can request control resources or
timing information, such as by transmitting an SRS and/or the like,
for maintaining timing of the target base station 302, and the
control resource assignor 308 can assign scheduling request
resources for the target base station 302 to the mobile device 304.
The device can desire handover, and the handover request receiver
310 can receive the request for handing-over communications. In one
example (e.g., an asynchronous wireless network detecting timing
difference from downlink channels), the request can be sent without
completely accurate timing and measures can be used to account for
the error as described previously (e.g., longer CP TTIs, HARQ
transmissions, etc.). The data resource scheduler 312 can schedule
and provide data communications channels to the device for
completing handover of the wireless communications without using a
RACH.
[0043] Mobile device 304 includes a gap requestor 314 that can
provide a base station with time intervals over which the mobile
device 304 will not be transmitting communication to the base
station and a target information receiver 316 that can
request/receive information related to a target base station, which
can include semi-static information utilized to monitor timing of
the base station. The mobile device can also include a target
resource requestor 318 that can request handover with the target
base station when an optimal handover time is determined. Moreover,
the mobile device 304 can be connected to a source base station 306
to facilitate wireless communication services.
[0044] According to an example, the mobile device 304 can be moving
throughout a sector hosted by the source base station 306. The
mobile device 304 can begin to detect additional base stations in
proximity and can desire to request information from the base
stations for subsequent handing-over thereto. Thus, the mobile
device 304 can utilize the gap requestor 314 to request
communication gaps with the source base station 306 over which the
mobile device 304 expects to transmit and receive data from one or
more disparate base stations, such as the target base station 302.
During these gaps, in one example, the mobile device 304 can
transmit an SRS to obtain information from the one or more base
stations regarding timing and the like. It is to be appreciated
that the gaps and request of such are not required; this is just
one possible example of obtaining information from the target base
station 302.
[0045] In one example, the target base station 302 can utilize the
control resource assignor 308 to establish the schedule request UL
channel with the target base station 302. Additionally, the mobile
device 304 can transmit an SRS to the target base station 302, and
the target information receiver 316 can obtain the transmitted
information and continually monitor the target base station 302 to
synchronize timing of the target base station 302. In one example,
the target information receiver 316 can obtain a response to a
transmitted SRS to determine information regarding a TA or other
timing information. Additionally, the mobile device 304 can
synchronize with the base station 302 based at least in part on the
receiving information or resources to facilitate subsequent handing
over. In another example, the network can be synchronized and
maintaining uplink timing towards multiple base stations such that
the cyclic prefix can accommodate timing difference due to
difference in propagation time between the serving and target base
stations. Additionally or alternatively, in a synchronous wireless
network, the timing can be substantially the same for the target
and source base stations such that timing detection is not needed.
It is to be appreciated that this can occur on the one or more base
stations such that the mobile device 304 can have an array of base
station information that can be utilized to determine a most
desirable base station for handing over communications. The base
station chosen for handover can be based on a TA that is closest to
the TA of the source base station 306, such that communications can
be significantly synchronized for handover. In one example, the TA
can be determined and compared by discerning a scrambling code for
the resource sent by the target base station 302 and comparing that
code to a scrambling code for the source base station 306.
[0046] As the mobile device 304 moves throughout the sector of the
source base station 306, it can move into closer range of the
target base station 302 and detect that handover to the target base
station 302 would be beneficial. This can be based at least in part
on signal strength, desired resources or services offered by the
target base station 302, and/or the like. The target resource
requestor 318 can transmit an initial handover message to the
target base station 302 over the assigned schedule request
resources using timing parameters (or TA) deduced from monitoring
the target base station 302. Thus, RACH is not required for
adjusting timing before requesting resources. It is to be
appreciated, as mentioned, that additional mechanisms can be
utilized (e.g., TTIs with strategically longer CPs, HARQ
transmissions, and the like) with the initial handover message to
account for minor timing error.
[0047] In one example, the target base station 302 can utilize
different sized cyclic prefixes in given time intervals to
compensate for greater error in timing of the initial handover
transmission from the mobile device 304; this can be a network
specification, specific to the target base station 302, etc. It is
to be appreciated that information regarding the cyclic prefix size
can be transmitted to mobile device 304 including broadcasting such
(e.g., on a broadcast channel) and the like. For example, the
information can be formatted such as a list of frames or TTIs
having short and/or long cyclic prefixes. In another example, the
information can comprise an offset from a current or initial frame
to the first long cyclic prefix TTI. Additionally, the target base
station 302 can dynamically configure the cyclic prefix
specifically for the handover. Using this information, the mobile
device 304 can handover to the target base station 302 and transmit
initial data during a long cyclic prefix TTI to attain a greater
possibility of successful communication (and therefore a successful
handover). Once the initial communication is transmitted, the data
resource scheduler 312 can schedule and return shared data channel
access to the mobile device 304 to facilitate wireless
communication service and complete handover from the source base
station 306. At this point, the timing utilized for transmitting
data to the target base station 302 can be more accurately
synchronized.
[0048] Now referring to FIG. 4, an example multiple-access wireless
communications network 400 is shown. The network 400 includes
multiple communications cells 402, 404, and 406 each having a
respective base station 408, 410, and 412 with multiple antennae to
support communications from a variety of devices. For example,
devices 414 and 416 in cell sector 402 can communicate with base
station 408, devices 418 and 420 initially in sector 404 can
communicate with base station 410, and devices 422 and 424 in
sector 406 can communicate with base station 412. In this example,
device 420 can be moving throughout the network 400. As the device
420 moves away from the base station 410, the signal can fade and
resources required to communicate with the base station 410 can
increase. As the device 420 moves toward base station 412, at some
point it may be advantageous to communicate instead with base
station 412 in sector 406; thus, the device 420 can be handed over
from sector 404 to sector 406 (and hence from base station 410 to
base station 412).
[0049] As described supra, the mobile device 420 can maintain and
monitor a list of cells (e.g., cells 408 and 412) to which it can
perform handover. For example, the mobile device 420 can initially
transmit an SRS to the cells to obtain TA information and/or the
like from the cells. In another example, this can be determined by
analyzing a scrambling code for the cell 408 and/or 412 and
comparing it to that of the current cell 410. In another example,
the mobile device 420 can calculate a timing difference between the
current cell 410 and cell 408 and/or 412 based at least in part on
the monitored cell information received as part of the SRS.
Additionally or alternatively, the mobile device 420 can maintain
synchronized timing with the cells 408 and 412 over granted
resources. When the mobile device 420 is sufficiently in range of
the disparate cell, 412, it can transmit request for data resources
over an assigned schedule request channel using the TA to adjust
any timing difference. Though the timing may not be precise, in
some examples, it can be generally close enough such that
technologies can be utilized to appropriately decode the
transmission. In one example, the base station 412 can utilize TTIs
with extended cyclic prefixes, and the mobile device 420 can
leverage these TTIs to transmit initial handover information.
[0050] However, extending cyclic prefixes can have an adverse
affect on throughput; thus, only certain TTIs can have the extended
cyclic prefixes in one example, and this information can be known
by the mobile device 402 (e.g. by broadcasting information
regarding the TTIs such as specific times of extended cyclic
prefixes, a pattern with or without an offset, and/or specific
occurrence) as described. In addition, TTIs having extended cyclic
prefix can be specially (e.g., dynamically) implemented upon
learning of the handover, in one example. Also, HARQ transmission
can be used to improve the reliability of the initial (and/or
subsequent) handover communications. It is to be appreciated that
following initial communications, more precise timing information
can be received and utilized by the mobile device 420 to ensure
reliable subsequent communication with the base station 412. In
this regard, handover is effectuated without using a RACH.
[0051] Referring to FIGS. 5-6, methodologies relating to handing
over communications by monitoring resources of a target (e.g.,
instead of a RACH) are illustrated. While, for purposes of
simplicity of explanation, the methodologies are shown and
described as a series of acts, it is to be understood and
appreciated that the methodologies are not limited by the order of
acts, as some acts may, in accordance with one or more embodiments,
occur in different orders and/or concurrently with other acts from
that shown and described herein. For example, those skilled in the
art will understand and appreciate that a methodology could
alternatively be represented as a series of interrelated states or
events, such as in a state diagram. Moreover, not all illustrated
acts may be required to implement a methodology in accordance with
one or more embodiments.
[0052] Turning to FIG. 5, illustrated is a methodology 500 that
facilitates requesting handover via a time synchronized request
based on received target resources or other information. At 502,
semi-static information is received from the target. For example,
this can relate to a response from transmitting an SRS that can be
analyzed to determine a TA or difference between TA of target and
source as described above. The information can additionally or
alternatively include C-RNTI; using this information, connected
entry into a cell related to the target can occur. At 504, the TA
is determined for the target as mentioned. The TA can help
synchronize communications with the target by comparing the TA of
the target to that of the source, or calculating a distance
therebetween and using the difference to synchronize an initial
handover message.
[0053] At 506, handover can be requested to the target based on the
TA. This can be done using the aforementioned mechanisms to
determine a timing difference or choosing a target that has a
similar TA as the source. In addition, as the comparison or
calculation may not produce a completely accurate synchronization
with the target, measures can be taken to increase likelihood of
successful communication. This includes using TTIs with longer
cyclic prefixes, HARQ transmissions, etc., as described supra. The
handover or scheduling request can be transmitted over an assigned
schedule request channel or other control channels related to the
target base station, in one example. At 508, the data resource
assignment is received allowing communications services to
transpire with the target. It is to be appreciated that once this
assignment is received, more accurate timing information is
received such to allow synchronized communication with the
target.
[0054] Now referring to FIG. 6, a methodology 600 that facilitates
handing over communications between a source and target access
point using target resources acquired before the handover is
illustrated. At 602, communication gaps are requested from a
source. For example, when communicating with the source, gaps can
be requested so that no communication with the source will occur in
the gap. At 604, a schedule request channel can be established with
a target during the gaps. Thus, as communication is not taking
place with the source, the target can be contacted for establishing
the channel. In one example, a sounding reference signal can be
sent, in a gap, to the target to establish the schedule request
channel during the gaps.
[0055] At 606, SRS information can be received on the target base
station. In response, the target base stations can provide TA to
the UE over the air and/or via the source base station, etc. As
mentioned, the SRS information can be utilized to determine a TA
difference or comparison of the target with the source, etc.
Additionally, C-RNTI can be received such that having the C-RNTI
and timing of the target, communications can be initially handed
over without using a RACH at 608. It is to be appreciated that once
handover occurs, more accurate timing information can be
received.
[0056] It will be appreciated that, in accordance with one or more
aspects described herein, inferences can be made regarding handing
over communications from a source base station to a target base
station for a mobile device as described. As used herein, the term
to "infer" or "inference" refers generally to the process of
reasoning about or inferring states of the system, environment,
and/or user from a set of observations as captured via events
and/or data. Inference can be employed to identify a specific
context or action, or can generate a probability distribution over
states, for example. The inference can be probabilistic--that is,
the computation of a probability distribution over states of
interest based on a consideration of data and events. Inference can
also refer to techniques employed for composing higher-level events
from a set of events and/or data. Such inference results in the
construction of new events or actions from a set of observed events
and/or stored event data, whether or not the events are correlated
in close temporal proximity, and whether the events and data come
from one or several event and data sources.
[0057] According to an example, one or more methods presented above
can include making inferences pertaining to from which devices to
request semi-static data, determining communications gaps to
request from a source base station, choosing a target base station
for handing over communications etc. Inferences can also be made
pertaining to calculating the timing difference between a source
and target base station, as well as determining a TTI using
extended cyclic prefixes to strategically transmit initial handover
data within, and/or the like.
[0058] FIG. 7 is an illustration of a mobile device 700 that
facilitates handing over communications utilizing requested
information from a target to transmit initial handover data. Mobile
device 700 comprises a receiver 702 that receives a signal from,
for instance, a receive antenna (not shown), performs typical
actions on (e.g., filters, amplifies, downconverts, etc.) the
received signal, and digitizes the conditioned signal to obtain
samples. Receiver 702 can comprise a demodulator 704 that can
demodulate received symbols and provide them to a processor 706 for
channel estimation. Processor 706 can be a processor dedicated to
analyzing information received by receiver 702 and/or generating
information for transmission by a transmitter 718, a processor that
controls one or more components of mobile device 700, and/or a
processor that both analyzes information received by receiver 702,
generates information for transmission by transmitter 718, and
controls one or more components of mobile device 700.
[0059] Mobile device 700 can additionally comprise memory 708 that
is operatively coupled to processor 706 and that can store data to
be transmitted, received data, information related to available
channels, data associated with analyzed signal and/or interference
strength, information related to an assigned channel, power, rate,
or the like, and any other suitable information for estimating a
channel and communicating via the channel. Memory 708 can
additionally store protocols and/or algorithms associated with
estimating and/or utilizing a channel (e.g., performance based,
capacity based, etc.).
[0060] It will be appreciated that the data store (e.g., memory
708) described herein can be either volatile memory or nonvolatile
memory, or can include both volatile and nonvolatile memory. By way
of illustration, and not limitation, nonvolatile memory can include
read only memory (ROM), programmable ROM (PROM), electrically
programmable ROM (EPROM), electrically erasable PROM (EEPROM), or
flash memory. Volatile memory can include random access memory
(RAM), which acts as external cache memory. By way of illustration
and not limitation, RAM is available in many forms such as
synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM
(SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM
(ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM).
The memory 708 of the subject systems and methods is intended to
comprise, without being limited to, these and any other suitable
types of memory.
[0061] Processor 706 can further be operatively coupled to a
schedule requestor 710 that can request scheduling resources from a
target base station as well as a target monitor 712 that can
evaluate communication with one or more targets to ensure correct
timing, etc. In one example, the mobile device can move throughout
a service area and evaluate base stations for handing over
communications. This can begin by using the schedule requestor 710
to establish an uplink schedule request channel with the base
station over which the mobile device 700 can receive grants for
resources, such as CQI resources, resources for data transmission
and reception, etc. In one example, the mobile device 700 can
transmit a SRS to obtain a TA for a target base station, which can
be subsequently utilized to request data resources over the
scheduling request channel; additionally, the mobile device 700
request communication gaps from a source base station over which to
sound the signal and receive establishment. The target monitor 712
can continually monitor the schedule request channel and/or
resources received in relation to the channel to have current
timing information for the target base station(s).
[0062] When the mobile device 700 determines handover to the
disparate base station would be beneficial (e.g., when a related
signal reaches a given threshold), in one example, a target can be
chosen from the target monitor 712 based at least in part on a
timing difference between the current source base station and the
target. Additionally, a timing adjuster 714 coupled to the
processor 706 can be utilized to determine a generally correct
timing for the target base station based at least in part on a
difference in time between the source and target base stations
(e.g., by evaluating their respective synchronization channels or
scrambling codes). The timing adjustor 714 can utilized the
determined adjustment to transmit an initial handover message. It
is to be appreciated that, as described previously, measures can be
taken at both ends to strengthen reliability of the initial
communication so more precise timing information can eventually be
received. Mobile device 700 still further comprises a modulator 716
and transmitter 718 that respectively modulate and transmit signals
to, for instance, a base station, another mobile device, etc.
Although depicted as being separate from the processor 706, it is
to be appreciated that the schedule requestor 710, target monitor
712, timing adjustor 714, demodulator 704, and/or modulator 716 can
be part of the processor 706 or multiple processors (not
shown).
[0063] FIG. 8 is an illustration of a system 800 that facilitates
granting resources and extended CP TTIs for mobile device handover.
The system 800 comprises a base station 802 (e.g., access point, .
. . ) with a receiver 810 that receives signal(s) from one or more
mobile devices 804 through a plurality of receive antennas 806, and
a transmitter 824 that transmits to the one or more mobile devices
804 through a transmit antenna 808. Receiver 810 can receive
information from receive antennas 806 and is operatively associated
with a demodulator 812 that demodulates received information.
Demodulated symbols are analyzed by a processor 814 that can be
similar to the processor described above with regard to FIG. 7, and
which is coupled to a memory 816 that stores information related to
estimating a signal (e.g., pilot) strength and/or interference
strength, data to be transmitted to or received from mobile
device(s) 804 (or a disparate base station (not shown)), and/or any
other suitable information related to performing the various
actions and functions set forth herein. Processor 814 is further
coupled to a schedule request responder 818 that can establish a
schedule request channel with one or more mobile devices 804 for
possible subsequent handover and a cyclic prefix selector 820 that
can specify longer CPs for certain TTIs to facilitate accounting
for minor timing errors during handover.
[0064] For instance, one or more mobile devices 804 can be in range
for handover and can request establishment of an uplink schedule
request channel. The schedule request responder 818 can establish
the channel with the mobile device 804. The mobile device 804 can
additionally transmit SRSs to the base station 802, and the base
station 802 can transmit information regarding certain resources
(e.g., TA, C-RNTI, etc.) over the channel. In addition, the cyclic
prefix selector 820 can establish one or more TTIs to have longer
CP to account for timing error in an initial handover communication
from the mobile device 804 based on the schedule request channel
and/or information received over the channel. For example, the
cyclic prefix selector 820 can specify longer CP for periodic TTIs,
requested TTIs, inferred TTIs based on a likelihood of handover,
for example, and/or the like. Furthermore, although depicted as
being separate from the processor 814, it is to be appreciated that
the schedule request responder 818, cyclic prefix selector 820,
demodulator 812, and/or modulator 822 can be part of the processor
814 or multiple processors (not shown).
[0065] FIG. 9 shows an example wireless communication system 900.
The wireless communication system 900 depicts one base station 910
and one mobile device 950 for sake of brevity. However, it is to be
appreciated that system 900 can include more than one base station
and/or more than one mobile device, wherein additional base
stations and/or mobile devices can be substantially similar or
different from example base station 910 and mobile device 950
described below. In addition, it is to be appreciated that base
station 910 and/or mobile device 950 can employ the systems (FIGS.
1-4 and 7-8) and/or methods (FIGS. 5-6) described herein to
facilitate wireless communication there between.
[0066] At base station 910, traffic data for a number of data
streams is provided from a data source 912 to a transmit (TX) data
processor 914. According to an example, each data stream can be
transmitted over a respective antenna. TX data processor 914
formats, codes, and interleaves the traffic data stream based on a
particular coding scheme selected for that data stream to provide
coded data.
[0067] The coded data for each data stream can be multiplexed with
pilot data using orthogonal frequency division multiplexing (OFDM)
techniques. Additionally or alternatively, the pilot symbols can be
frequency division multiplexed (FDM), time division multiplexed
(TDM), or code division multiplexed (CDM). The pilot data is
typically a known data pattern that is processed in a known manner
and can be used at mobile device 950 to estimate channel response.
The multiplexed pilot and coded data for each data stream can be
modulated (e.g., symbol mapped) based on a particular modulation
scheme (e.g., binary phase-shift keying (BPSK), quadrature
phase-shift keying (QPSK), M-phase-shift keying (M-PSK),
M-quadrature amplitude modulation (M-QAM), etc.) selected for that
data stream to provide modulation symbols. The data rate, coding,
and modulation for each data stream can be determined by
instructions performed or provided by processor 930.
[0068] The modulation symbols for the data streams can be provided
to a TX MIMO processor 920, which can further process the
modulation symbols (e.g., for OFDM). TX MIMO processor 920 then
provides N.sub.T modulation symbol streams to N.sub.T transmitters
(TMTR) 922a through 922t. In various embodiments, TX MIMO processor
920 applies beamforming weights to the symbols of the data streams
and to the antenna from which the symbol is being transmitted.
[0069] Each transmitter 922 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. Further, N.sub.T modulated signals from
transmitters 922a through 922t are transmitted from N.sub.T
antennas 924a through 924t, respectively.
[0070] At mobile device 950, the transmitted modulated signals are
received by N.sub.R antennas 952a through 952r and the received
signal from each antenna 952 is provided to a respective receiver
(RCVR) 954a through 954r. Each receiver 954 conditions (e.g.,
filters, amplifies, and downconverts) a respective signal,
digitizes the conditioned signal to provide samples, and further
processes the samples to provide a corresponding "received" symbol
stream.
[0071] An RX data processor 960 can receive and process the N.sub.R
received symbol streams from N.sub.R receivers 954 based on a
particular receiver processing technique to provide N.sub.T
"detected" symbol streams. RX data processor 960 can demodulate,
deinterleave, and decode each detected symbol stream to recover the
traffic data for the data stream. The processing by RX data
processor 960 is complementary to that performed by TX MIMO
processor 920 and TX data processor 914 at base station 910.
[0072] A processor 970 can periodically determine which precoding
matrix to utilize as discussed above. Further, processor 970 can
formulate a reverse link message comprising a matrix index portion
and a rank value portion.
[0073] The reverse link message can comprise various types of
information regarding the communication link and/or the received
data stream. The reverse link message can be processed by a TX data
processor 938, which also receives traffic data for a number of
data streams from a data source 936, modulated by a modulator 980,
conditioned by transmitters 954a through 954r, and transmitted back
to base station 910.
[0074] At base station 910, the modulated signals from mobile
device 950 are received by antennas 924, conditioned by receivers
922, demodulated by a demodulator 940, and processed by a RX data
processor 942 to extract the reverse link message transmitted by
mobile device 950. Further, processor 930 can process the extracted
message to determine which precoding matrix to use for determining
the beamforming weights.
[0075] Processors 930 and 970 can direct (e.g., control,
coordinate, manage, etc.) operation at base station 910 and mobile
device 950, respectively. Respective processors 930 and 970 can be
associated with memory 932 and 972 that store program codes and
data. Processors 930 and 970 can also perform computations to
derive frequency and impulse response estimates for the uplink and
downlink, respectively.
[0076] It is to be understood that the embodiments described herein
can be implemented in hardware, software, firmware, middleware,
microcode, or any combination thereof. For a hardware
implementation, the processing units can be implemented within one
or more application specific integrated circuits (ASICs), digital
signal processors (DSPs), digital signal processing devices
(DSPDs), programmable logic devices (PLDs), field programmable gate
arrays (FPGAs), processors, controllers, micro-controllers,
microprocessors, other electronic units designed to perform the
functions described herein, or a combination thereof.
[0077] When the embodiments are implemented in software, firmware,
middleware or microcode, program code or code segments, they can be
stored in a machine-readable medium, such as a storage component. A
code segment can represent a procedure, a function, a subprogram, a
program, a routine, a subroutine, a module, a software package, a
class, or any combination of instructions, data structures, or
program statements. A code segment can be coupled to another code
segment or a hardware circuit by passing and/or receiving
information, data, arguments, parameters, or memory contents.
Information, arguments, parameters, data, etc. can be passed,
forwarded, or transmitted using any suitable means including memory
sharing, message passing, token passing, network transmission,
etc.
[0078] For a software implementation, the techniques described
herein can be implemented with modules (e.g., procedures,
functions, and so on) that perform the functions described herein.
The software codes can be stored in memory units and executed by
processors. The memory unit can be implemented within the processor
or external to the processor, in which case it can be
communicatively coupled to the processor via various means as is
known in the art.
[0079] With reference to FIG. 10, illustrated is a system 1000 that
facilitates handing over mobile communications in a wireless
network without using a RACH. For example, system 1000 can reside
at least partially within a base station, mobile device, etc. It is
to be appreciated that system 1000 is represented as including
functional blocks, which can be functional blocks that represent
functions implemented by a processor, software, or combination
thereof (e.g. firmware). System 1000 includes a logical grouping
1002 of electrical components that can act in conjunction. For
instance, logical grouping 1002 can include an electrical component
for receiving wireless communications service from a source base
station 1004. For example, the system 1000 can communicate with the
base station over one or more channels, as described above, to
effectuate wireless communication service. Further, logical
grouping 1002 can comprise an electrical component for receiving
multiple assigned uplink control channels for transmitting schedule
request signals to a plurality of target base stations 1006. For
example, the resources can relate to handing over communications to
the target base station. Additionally, other resources of the
target base station can be monitored by transmitting SRS or
determining TA information for the target base station, for
example. Moreover, logical grouping 1002 can comprise an electrical
component for transmitting a scheduling request to a selected
target base station of the plurality of target base stations over
at least one of the assigned uplink control channels 1008. For
example, the TA of the target base station can be utilized in
transmitting the scheduling request for more efficient handover.
Additionally, system 1000 can include a memory 1010 that retains
instructions for executing functions associated with electrical
components 1004, 1006, and 1008. While shown as being external to
memory 1010, it is to be understood that one or more of electrical
components 1004, 1006, and 1008 can exist within memory 1010.
[0080] What has been described above includes examples of one or
more embodiments. It is, of course, not possible to describe every
conceivable combination of components or methodologies for purposes
of describing the aforementioned embodiments, but one of ordinary
skill in the art may recognize that many further combinations and
permutations of various embodiments are possible. Accordingly, the
described embodiments are intended to embrace all such alterations,
modifications and variations that fall within the spirit and scope
of the appended claims. Furthermore, to the extent that the term
"includes" is used in either the detailed description or the
claims, such term is intended to be inclusive in a manner similar
to the term "comprising" as "comprising" is interpreted when
employed as a transitional word in a claim.
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