U.S. patent application number 13/369860 was filed with the patent office on 2012-05-31 for method of a serving base station for facilitating a mobile station to perform a fast handoff.
This patent application is currently assigned to MOTOROLA MOBILITY, INC.. Invention is credited to William P. Alberth, JR., Lorenzo A. Ponce De Leon.
Application Number | 20120135735 13/369860 |
Document ID | / |
Family ID | 40436362 |
Filed Date | 2012-05-31 |
United States Patent
Application |
20120135735 |
Kind Code |
A1 |
Ponce De Leon; Lorenzo A. ;
et al. |
May 31, 2012 |
Method of a Serving Base Station for Facilitating a Mobile Station
to Perform a Fast Handoff
Abstract
A method for facilitating a mobile station to perform a fast
handoff in a wireless communication system allows a handoff
procedure to be anticipated (by the mobile station, its serving
base station, or both) based on historical information regarding
prior successful handoff procedures. In operation, the serving base
station monitors (510) current mobile station parameters and
compares them with historical data. If the parameters indicate a
high probability target base station (515), the serving base
station requests allocation (525) of air interface resources at the
high probability target base station prior to the mobile station
reporting reception of signal from the high probability target base
station. This facilitates fast handoff from the serving base
station to the high probability target base station.
Inventors: |
Ponce De Leon; Lorenzo A.;
(Lake Worth, FL) ; Alberth, JR.; William P.;
(Prairie Grove, IL) |
Assignee: |
MOTOROLA MOBILITY, INC.
Libertyville
IL
|
Family ID: |
40436362 |
Appl. No.: |
13/369860 |
Filed: |
February 9, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11957652 |
Dec 17, 2007 |
8140076 |
|
|
13369860 |
|
|
|
|
Current U.S.
Class: |
455/436 |
Current CPC
Class: |
H04W 48/16 20130101;
H04W 36/30 20130101 |
Class at
Publication: |
455/436 |
International
Class: |
H04W 36/32 20090101
H04W036/32 |
Claims
1. A method of a serving base station for facilitating a mobile
station to perform a fast handoff, comprising: determining a high
probability target base station with which the mobile station is
most likely to perform handoff based on a historical data;
requesting allocation of air interface resources at the high
probability target base station to the mobile station, prior to the
mobile station reporting reception of signals from the high
probability target base station, to facilitate the mobile station
to perform the fast handoff with the high probability target base
station.
2. The method of claim 1, wherein if a handoff procedure with the
high probability target base station is successful within a
predefined time period, updating the historical data to reflect a
successful handoff of the mobile station to the high probability
target base station.
3. The method of claim 2, wherein updating the historical data
comprises: increasing a weighting factor in the historical data
associated with the high probability target base station for the
mobile station.
4. The method of claim 1, wherein the determining includes:
examining at least one current mobile station parameter, wherein
the at least one current mobile station parameter relates to at
least one of: a serving base station identification, smart antenna
information, a speed of mobility of the mobile station, a direction
of mobility of the mobile station, or a location of the mobile
station; and comparing the at least one current mobile station
parameter with at least one past mobile station parameter in the
historical data.
5. The method of claim 1, wherein when a handoff procedure with the
high probability target base station is not successful within a
predefined time period, updating the historical data to reflect an
unsuccessful handoff of the mobile station to the high probability
target base station.
6. The method of claim 5, wherein updating the historical data
comprises: decreasing a weighting factor in the historical data
associated with the high probability target base station for the
mobile station.
7. The method of claim 5, further comprising: requesting
de-allocation of air interface resources at the high probability
target base station.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/957,652 entitled "Method for Facilitating a Mobile
Station to Perform a Fast Handoff" filed on Dec. 17, 2007 by
Lorenzo A. Ponce de Leon et al. and claims the benefit thereof.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates generally to communication
networks, and more particularly to facilitating mobile stations to
perform fast handoff in communication networks.
BACKGROUND
[0003] Wireless communications networks, such as mobile wireless
telephone networks, have become increasingly prevalent over the
past decade. A wireless communication network, such as an
infrastructure-based wireless network, typically includes a
communication network with fixed and wired gateways. Many wireless
networks employ a wireless device or terminal which communicates
with a base station that is coupled to a wired network. The
wireless device can move geographically while it is communicating
over a wireless link to the base station. When the wireless device
moves out of range of one base station, it may connect or "handoff"
(sometimes called "handover") to a new base station and start
communicating with the wired network through the new base station.
In order to be ready for a potential handoff, the wireless device
may continually background scan for an available base station.
Wireless devices have limited energy reserves, however they must
actively interface with a network to establish link and transfer
data. A network environment in a wireless link is spatial, dynamic,
and stochastic. Continually scanning for available base stations
may place a strain on the wireless device's energy reserves and
increase its power consumption which may further reduce the life
span and overall performance of the wireless device.
[0004] In addition, the long latency period associated with the
handoff is undesirable for wireless devices as this may prevent
running of certain applications and interrupt data transfer between
the wireless device and the network. The wireless device therefore
expends energy and time in establishing and maintaining links prior
to and after data transfers. Multimode wireless devices have the
additional problem of covering many bands and interfacing with
networks asynchronously, thereby adding additional load to the
device's energy resources. In some cases, multimode wireless
devices may be "blind" for a period of time to all the network
services available at a locale. Accordingly there is a need to
facilitate the wireless devices to perform fast handoff while
optimizing the energy expenditure associated with establishing and
monitoring links in wireless networks.
BRIEF DESCRIPTION OF THE FIGURES
[0005] The accompanying figures, where like reference numerals
refer to identical or functionally similar elements throughout the
separate views, together with the detailed description below, are
incorporated in and form part of the specification, and serve to
further illustrate embodiments of concepts that include the claimed
invention, and explain various principles and advantages of those
embodiments.
[0006] FIG. 1 is a block diagram of a wireless communication system
in accordance with some embodiments.
[0007] FIG. 2 is a block diagram of a mobile station in
communication with a base station in accordance with some
embodiments.
[0008] FIG. 3 is a structure of historical data in accordance with
some embodiments.
[0009] FIG. 4 is a flowchart of a method for facilitating a mobile
station to perform fast handoff in accordance with some
embodiments.
[0010] FIG. 5 is a flowchart of a method for a base station to
facilitate a mobile station to perform fast handoff in accordance
with some embodiments.
[0011] Skilled artisans will appreciate that elements in the
figures are illustrated for simplicity and clarity and have not
necessarily been drawn to scale. For example, the dimensions of
some of the elements in the figures may be exaggerated relative to
other elements to help to improve understanding of embodiments of
the present invention.
[0012] The apparatus and method components have been represented
where appropriate by conventional symbols in the drawings, showing
only those specific details that are pertinent to understanding the
embodiments of the present invention so as not to obscure the
disclosure with details that will be readily apparent to those of
ordinary skill in the art having the benefit of the description
herein.
DETAILED DESCRIPTION
[0013] The present invention provides a method for facilitating a
mobile station to perform a fast handoff in a wireless
communication system. A mobile station is configured to monitor its
network environment and store a history of the network environment
in memory. The mobile station can use its historical data to
minimize the energy spent to establish the parameters of the local
network environment. In operation, the mobile station receives a
neighbor list from a serving base station. The neighbor list
includes a list of base station that may be neighboring to the
serving base station and may include both base stations of the
current network and base stations of different networks and/or
different radio access technologies (RATs). The mobile station then
determines whether a member base station of the neighbor list is a
"successful" target base station based on historical data (i.e.,
that handoff to that target base station has previously been
successful). If the mobile station determines that the member base
station is not a successful target base station, then the mobile
station background scans the member base station and measures a
signal quality associated with the member base station, and further
sends a measurement report for the member base station when the
signal quality meets a standard signal quality threshold. In a case
when the mobile station determines that the member base station is
a "successful" target base station, the mobile station sends the
measurement report as soon as the measured signal quality meets a
signal quality threshold that is lower than the standard signal
quality threshold.
Wireless Communication System
[0014] FIG. 1 is a block diagram illustrating one example of a
wireless communication system 100. The wireless communication
system 100 includes a coverage area divided into a plurality of
cells 110-1 through 110-n. Each cell 110-n is served by a base
station 120-n. For example, as shown in FIG. 1, the cells 110-1,
110-2, 110-3, 110-4, 110-5, and 110-6 are served by their
respective base stations 120-1, 120-2, 120-3, 120-4, 120-5, and
120-6. Each base station 120-n connects the mobile stations 130-n
present in the corresponding cell 110-n with a communication
network through a mobile switching center 140. In the example of
FIG. 1, the mobile stations 130-1 and 130-2 present in the cell
110-1 are served by the base station 120-1. The mobile switching
center 140 can connect the mobile station 130-1 to other networks
150 such as a public switched telephone network (PSTN). As the
mobile stations 130-n move geographically across the communication
system, the mobile stations 130-n can handoff to different base
stations 120 of the wireless communication system 100. According to
some embodiments of the present invention, the mobile stations
130-n are facilitated to perform fast handoff with the base
stations 120-n as the mobile stations traverse through the cells
110-n of the wireless communication system 100. For example, the
wireless communication system 100 may facilitate the mobile station
130 to perform fast handoff with each of the base stations 120-1,
120-4, and 120-5, and 120-6 when the mobile station 130-1 traverses
through the cells 110-1, 110-4, 110-5, and 110-6 via road XYZ 160
as shown in FIG. 1.
Components of Mobile Station and Base Station
[0015] Now referring to FIG. 2, the mobile station 130 is shown in
communication with the base station 120. The mobile station 130 and
the base station 120 are in communication with each other through a
radio link 205. The mobile station 130 may be any type of wireless
communication device including, but not limited to, cellular,
mobile, and wireless telephones; PCs (personal computers), laptop,
notebook, and wearable computers with wireless modems, PDAs
(personal digital assistants) with wireless modems; and pagers. For
example, the mobile station 130 may include digital systems to
secure fast wireless transmissions of voice and/or data.
[0016] The base station 120 may be any wireless communication
station installed at a fixed location of the wireless communication
system 100. The base station is sometimes referred to as a radio
base station or Node B (in 3G networks), or access point base
station, or an infrastructure device.
[0017] The mobile station 130 comprises a processor 210, a
transceiver 215 including a transmitter circuitry 217 and a
receiver circuitry 219, an antenna 220, a memory 225, a scanner
230, and the neighbor list report trigger 235. The base station 120
includes a processor 260, a transceiver 265 including a transmitter
circuitry 267 and a receiver circuitry 269, an antenna 270 which
may be an omni, sector, MIMO, or smart antenna array, and a memory
275. Although not shown, the base station 120 and the mobile
station 130 also can include an antenna switch, duplexer,
circulator, or other highly isolative means (not shown) for
intermittently providing information packets from the transmitter
circuitry 217, 267 to the antenna 220, 270 and from the antenna
220, 270 to the receiver circuitry 219, 269. The mobile station 130
or the base station 120 is an integrated unit containing at least
all the elements depicted in FIG. 2, as well as any other elements
necessary for the mobile station 130 or the base station 120 to
perform its particular electronic function. For example, the mobile
station 130 would include a user interface (not shown) including a
display, keypad, loudspeaker, and/or microphone. Alternatively, the
mobile station 130 or the base station 120 can comprise a
collection of appropriately interconnected units or devices,
wherein such units or devices perform functions that are equivalent
to the functions performed by the elements of the mobile station
130 or the base station 120.
[0018] The base station 120 stores neighbor list information 277 in
the memory 275. In one embodiment, the neighbor list information
277 includes a list of base stations that are neighboring to the
base station 120. For example, the neighbor list information 277 of
base station 120-4 may include base stations 120-1, 120-2, 120-3,
120-5, and 120-6. The neighbor list information 277 is periodically
transmitted from the base station 120 to the mobile station 130.
The mobile station 130 stores received neighbor list information
227 in the memory 225. The mobile station 130 may periodically
update the received neighbor list information 227 based on the
neighbor list information 277 received from the base station
120.
[0019] The scanner 230 of the mobile station 130 scans the base
stations 120 listed in the received neighbor list information 227
when the mobile station 130 is in a background scanning mode, and
measures the signal quality associated with the scanned base
stations 120. The neighbor list report trigger 235 triggers a
measurement report for a scanned base station as soon as the signal
quality associated with the scanned base station meets a signal
quality threshold, wherein the signal quality threshold is either a
standard signal quality threshold or a lower signal quality
threshold. In embodiments of the present invention, the lower
signal quality threshold is simply a predetermined threshold that
is lower than the standard signal quality threshold.
[0020] The processor 210, 260 includes one or more microprocessors,
microcontrollers, DSPs (digital signal processors), state machines,
logic circuitry, or any other device or devices that process
information based on operational or programming instructions. Such
operational or programming instructions are stored in the memory
225, 275. The memory 225, 275 can be an IC (integrated circuit)
memory chip containing any form of RAM (random-access memory) or
ROM (read-only memory), a floppy disk, a CD-ROM (compact disk
read-only memory), a hard disk drive, a DVD (digital video disc), a
flash memory card, external subscriber identity module (SIM) card
or any other medium for storing digital information. One of
ordinary skill in the art will recognize that when the processor
210, 260 has one or more of its functions performed by a state
machine or logic circuitry, the memory 225, 275 containing the
corresponding operational instructions can be embedded within the
state machine or logic circuitry. The operations performed by the
processor 210, 260 and the other elements of the mobile station 130
and the base station 120 are described in detail below.
[0021] The transmitter circuitry 217, 267 and the receiver
circuitry 219, 269 enable the mobile station 130 and the base
station 120 to communicate information packets to and acquire
information packets from the base stations 120 or mobile stations
130, respectively. In this regard, the transmitter circuitry 217,
267 and the receiver circuitry 219, 269 include appropriate,
conventional circuitry to enable digital or analog transmissions
over a wireless communication channel. One of ordinary skill in the
art will recognize that most, if not all, of the functions of the
transmitter circuitry 217, 267 and/or the receiver circuitry 219,
269 can be implemented in a processor, such as the processor 210,
260. However, the processor 210, 260, the transmitter circuitry
217, 267, and the receiver circuitry 219, 269 have been
artificially partitioned herein to facilitate a better
understanding.
[0022] The receiver circuitry 219, 269 is capable of receiving
radio frequency (RF) signals from at least one frequency band using
a RAT and optionally multiple frequency bands or RATs. The receiver
circuitry 219, 269 can optionally comprise a first receiver and a
second receiver, or one receiver capable of receiving in two or
more frequency bands and/or RATs. The transceiver 215, 265 includes
at least one set of transmitter circuitry 217, 267. The at least
one transmitter 215, 265 can be capable of transmitting to multiple
devices potentially in multiple frequency bands or RATs.
[0023] The antenna 220, 270 comprises any known or developed
structure for radiating and receiving electromagnetic energy in the
frequency range containing the wireless carrier frequencies. Even
though only one antenna 220, 270 is shown, any number of antennas
may interface with the transceiver 215, 265. Thus, the depiction of
one antenna 220, 270 is not meant to be a limitation on an
embodiment of the present invention.
Historical Data
[0024] Historical data 229 stored in a mobile station 130 would
include at least an identification of the serving base station and
the identification of the most likely target base station for
handoff. The base station identification could be a BSID, a serial
number, or any other identifying number. Historical data 229 in the
mobile station 130 may also include current location information,
direction of travel, and a history of handoffs and acquired
networks associated with the location and/or direction of travel.
Historical data 279 may be stored in a base station 120 or
elsewhere on the network and would include information similar to
historical data 229. Historical data 229 may also include a list of
mobile station identifications, a history of how they have handed
off through the network, and may also include information from
smart antenna array settings in the base station.
[0025] The mobile station 130 and/or the base station 120 may store
its respective historical data 229, 279 in memory 225, 275. In one
embodiment, the historical data 229, 279 may be stored in an
infrastructure within the wireless communication system, wherein
the infrastructure may be a device other than the base station 120
and the mobile station 130, and further wherein the historical data
229, 279 stored in the infrastructure is accessible by the base
station 120 and/or the mobile station 130.
[0026] Referring now to FIG. 3, an extract of a structure of the
historical data 229, 279 is shown. The historical data 229, 279
includes information related to past mobile station parameters 310
which are collected during previous operation of the mobile station
130. The past mobile station parameters 310 include, but are not
limited to, a serving base station identification 315, a speed 320
of the mobility of the mobile station 130, a direction 325 of the
mobility of the mobile station 130, a location 135 of the mobile
station 130, or one or more roads 335 traversed by the mobile
station 130 during the historical visit. The historical data 229,
279 may further include smart antenna information (not shown). The
smart antenna information includes information related to selected
antennas from an array of antennas for communication with the base
station during historical visits of the mobile station 130. In one
example, the mobile station 130 may select the antenna based on a
direction of arrival (DoA) of a signal associated with the serving
base station.
[0027] The historical data 229, 279 may further include a list 340
of "successful" base stations for handoff corresponding to the past
mobile station parameters 310 during historical visits of the
mobile station 130.
Weighting Factor
[0028] In one embodiment, each of the successful base stations in
the list 340 may be provided a weighting factor, wherein the
weighting factor represents a historically-determined success rate
of handoff of the particular mobile station 130 to the base
stations 120. For example, whenever the mobile station 130 performs
a successful handoff with a target base station stored in the
historical data 229, 279, then the historical data 229, 279 is
updated to increase the weighting factor associated with the target
base station. On the other hand, when the handoff is not
successful, then the historical data 229, 279 can be updated to
decrease the weighting factor to reflect the unsuccessful handoff
of the mobile station 130 to the target base station. In one
implementation of the present invention, the weighting factor
associated with the target base station remains unaltered until the
mobile station performs a successful handoff with the target base
station; and when the mobile station performs a successful handoff
with a target base station, the weighting factor associated with
the target base station is increased to reflect the successful
handoff of the mobile station to the target base station.
[0029] As shown in FIG. 3 and referring to FIG. 1, according to one
example, the historical data 229, 279 denotes that the mobile
station 130-1 has successfully performed handoff with the base
station 120-4 with a weighting factor 0.8 as against a weighting
factor 0.6 for the base station 120-2. Therefore, when currently
traveling with mobile station parameters that are similar to a past
mobile station parameter 310 of (120-1, 42, S->N, 35.5, -105,
Road XYZ . . . ), the mobile station 130-1 is most likely to
perform a successful handoff with the base station 120-4 compared
to the other base stations 120-n. In another example, when
currently traveling with mobile station parameters that closely
match the past mobile station parameter 310 of (120-5, 32, E->W,
43.6, -96.7, Road XYZ . . . ), the mobile station 130-1 may prefer
handing off to base station 120-4 rather than to base station
120-2, because, for this particular past mobile station parameter,
the weighting factor (0.2) for the base station 120-4 is higher
than the weighting factor (0.1) associated with the base station
120-2.
Flowchart of Mobile Station Method to Facilitate Fast Handoff
[0030] FIG. 4 is a flowchart of a method 400 for facilitating a
mobile station 130 to perform fast handoff in accordance with some
embodiments. The method 400 begins at step 405, where a mobile
station 130 is in a call with a serving base station 120. At step
410, the mobile station 130 receives neighbor list information 227
from the serving base station 120. Next at step 415, the mobile
station 130 monitors at least one current mobile station parameter
and determines one or more successful target base stations by
comparing the current mobile station parameters with its historical
data 229. In one example, the mobile station 130 determines one or
more successful target base stations by monitoring at least one
current mobile station parameter including, but not limited to, a
serving base station identification, smart antenna information, a
speed of the mobility of the mobile station 130, a direction of
mobility of the mobile station 130, a location of the mobile
station 130, and comparing the at least one current mobile station
parameter with at least one past mobile station parameter 310 in
the historical data 229. In one embodiment, a historical base
station included in the historical data 229 is a successful target
base station when a weighting factor associated with the historical
base station exceeds a predefined weighting factor, and further
when the at least one current mobile station parameter matches the
at least one past mobile station parameter 310. The predefined
weighting factor may be different depending on the cell 110-n the
mobile station 130 is currently associated with.
[0031] Next at step 420, the mobile station 130 determines whether
a member base station in the received neighbor list information 227
is a (previously) successful target base station. If the member
base station is not the successful target base station, then at
step 425, the mobile station 130 background scans the member base
station and measures a signal quality associated with the member
base station. As can be appreciated by a person of ordinary skill
in the art, step 425 is a periodic process and therefore, the
mobile station 130 may re-scan the member base station after a
first time period interval (T.sub.1). At step 430, the mobile
station 130 determines whether the measured signal quality for the
member base station meets the standard signal quality threshold. If
the measured signal quality threshold does not meet the standard
signal quality threshold, then the mobile station 130 proceeds to
determine if a next member base station in the neighbor list 227 is
a successful target base station as shown in step 420. On the other
hand, if the mobile station determines that the measured signal
quality threshold meets the standard signal quality threshold, then
the mobile station 130 proceeds to step 460 and sends a measurement
report for the member base station to the serving base station
120.
[0032] Referring back to step 420, if the mobile station 130
determines that the member station is a (previously) successful
target base station, then at step 435, the mobile station 130
background scans the member base station and measures a signal
quality associated with the member base station. As can be
appreciated by a person skilled in the art, step 435 is a periodic
process, and therefore, the mobile station 130 may re-scan the
member base station after a second time period interval (T.sub.2).
In this embodiment, the second time period (T.sub.2) is shorter
than the first time period interval (T.sub.1) i.e. T.sub.2<T1.
Next at step 440, the mobile station 130 determines whether the
measured signal quality threshold meets the standard signal quality
threshold. If the measured signal quality threshold meets the
standard signal quality threshold, then the mobile station 130
proceeds to step 460 to send a measurement report for the member
base station to the serving base station. On the other hand, if the
measured signal quality threshold does not meet the standard signal
quality threshold, then at step 445, the mobile station 130
determines whether the measured signal quality threshold meets the
lower signal quality threshold. If the measured signal threshold
does not meet the lower signal quality threshold, then the mobile
station 130 proceeds to step 420 to determine if a next member base
station in the neighbor list 227 is a successful target base
station.
[0033] Referring back to step 445, when the mobile station 130
determines that the measured signal quality threshold meets the
lower signal quality threshold, then the mobile station proceeds to
step 450 to determine whether the member base station is capable of
pre-reserving air interface resources. If the member base station
is capable of pre-reserving air interface resources, then the
mobile station 130 proceeds to step 460 to send a measurement
report for the member base station to the serving base station. On
the other hand, if the member base station is not capable of
pre-reserving air interface resources, then at step 455, the mobile
station 130 artificially inflates the measured signal quality
measurement to reach the standard signal quality threshold. Next at
step 460, the mobile station 130 sends the artificially inflated
measurement report for the member base station to the serving base
station.
[0034] Next at 465, the mobile station 130 receives a handoff
command from the serving base station in response to the
measurement report for the member base station. The mobile station
130 then proceeds to step 470 to perform a handoff procedure with
the member base station. Next at step 475, the mobile station 130
determines whether the handoff to the member base station is
successful. If the handoff to the member base station is
successful, then the mobile station 130 updates the historical data
229 to reflect successful handoff of the mobile station 130 to the
member base station. In one example, the mobile station 130 updates
the historical data 229 by increasing the weighting factor
associated with the member base station. In one embodiment, if the
weighting factor associated with a target base station increases
beyond an upper weighting factor threshold, then the weighting
factor is not increased even if there are subsequent successful
handoffs of the member base station to the target base station. On
the other hand, if the handoff to the member base station is not
successful, then the mobile station 130 updates the historical data
229, 279 to reflect unsuccessful handoff of the mobile station to
the member base station. In one example, the mobile station 130
updates its historical data 229 by decreasing the weighting factor
associated with the member base station. In another example, if the
weighting factor associated with a target base station decreases
below a lower weighting factor threshold, then the weighting factor
is not decreased even if there are subsequent unsuccessful handoffs
to the target base station.
Flowchart of Base Station Method to Facilitate Fast Handoff
[0035] FIG. 5 is a flowchart of a method 500 for a base station 120
to facilitate a mobile station 130 to perform fast handoff in
accordance with some embodiments. The method begins at step 505,
where a mobile station 130 is in a call and served by a base
station 120. At step 510, the base station 120 monitors current
mobile station parameters and compares the current mobile station
parameters with its historical data 279. Next at step 515, the base
station 120 determines whether a high probability target base
station exists by comparing the current mobile station parameter(s)
with historical mobile station parameters 310. The high probability
target base station would be the target base station with the
highest weighting factor and may require the weighting factor to
exceed a predefined threshold. In an alternate embodiment, any base
stations which have weighting factors that exceed a threshold may
be considered a high probability target base station. In one
example, the base station 120 determines a high probability target
base station by examining at least one of a serving base station
identification, smart antenna information, a speed of the mobility
of the mobile station 130, a direction of mobility of the mobile
station 130, or a location of the mobile station 130, and comparing
the at least one current mobile station parameter with at least one
past mobile station parameter 310 in the historical data 279. If a
high probability target base station does not exist for the current
mobile station parameter(s), then at step 520, the base station 120
facilitates the mobile station 130 to undergo normal handoff using
standard handoff procedures.
[0036] On the other hand, if the base station 120 determines that a
high probability target base station exists for the current mobile
station parameter, then the base station 120 anticipates that the
mobile station 130 will handoff to the high probability target base
station prior to the mobile station 130 reporting reception of
signals from the high probability target base station. Next at step
525, the base station 120 requests allocation of air interface
resources at the high probability target base station to facilitate
the mobile station 130 to undergo fast handoff with the high
probability target base station.
[0037] Next at step 530, the base station 120 determines whether
the handoff of the mobile station 130 to the high probability
target base station is successful within a predetermined time
period. If the handoff of the mobile station 130 to the high
probability target base station is successful within the
predetermined time period, the base station 120 updates the
historical data 279 to reflect a successful handoff of the mobile
station 130 to the high probability target base station. In one
example, the base station 120 updates the historical data 279 by
increasing the weighting factor associated with the high
probability target base station. In one embodiment, if the
weighting factor associated with a target base station increases
beyond an upper weighting factor threshold, then the weighting
factor is not increased even if there are subsequent successful
handoffs of the mobile station 130 to the high probability base
station. On the other hand, if the base station 120 determines that
the handoff of the mobile station 130 to the high probability
target base station is not successful within the predefined time
period, then at step 540, the base station 120 requests
de-allocation of the air interfaces at the high probability base
station and updates the historical data 279 to reflect unsuccessful
handoff of the mobile station 130 to the high probability target
base station. In one example, the mobile station 130 updates the
historical data 229 by decreasing the weighting factor associated
with the high probability target base station. In one embodiment,
if the weighting factor associated with the high probability target
base station decreases below a lower weighting factor threshold,
then the weighting factor is not decreased even if there are
subsequent unsuccessful handoffs of the mobile station 130 to the
high probability target base station.
[0038] Thus, the mobile station is facilitated to perform handoff
with a target base station as quickly as possible, thereby reducing
the long latency period associated with the handoff. Additionally,
by attempting handoff to a target base station that has
historically been successful under similar mobile station
circumstances, the probability of a dropped call is reduced.
Various implementation of the present invention further reduces the
strain on the mobile station's energy reserves used for background
scanning while optimizing the energy expenditure associated with
establishing and monitoring links in wireless networks.
[0039] In implementations where a high probability target base
station pre-reserves air interface resources in anticipation of a
mobile station being handed off to it, the pre-reservation of air
interface resources is offset by a high probability of a handoff
procedure completing successfully within a predefined time limit.
Without pre-reservation, in some network topographies, a user would
experience a dropped call.
[0040] In the foregoing specification, specific embodiments have
been described. However, one of ordinary skill in the art
appreciates that various modifications and changes can be made
without departing from the scope of the invention as set forth in
the claims below. Accordingly, the specification and figures are to
be regarded in an illustrative rather than a restrictive sense, and
all such modifications are intended to be included within the scope
of present teachings. The benefits, advantages, solutions to
problems, and any element(s) that may cause any benefit, advantage,
or solution to occur or become more pronounced are not to be
construed as a critical, required, or essential features or
elements of any or all the claims. The invention is defined solely
by the appended claims including any amendments made during the
pendency of this application and all equivalents of those claims as
issued.
[0041] Moreover in this document, relational terms such as first
and second, top and bottom, and the like may be used solely to
distinguish one entity or action from another entity or action
without necessarily requiring or implying any actual such
relationship or order between such entities or actions. The terms
"comprises," "comprising," "has", "having," "includes",
"including," "contains", "containing" or any other variation
thereof, are intended to cover a non-exclusive inclusion, such that
a process, method, article, or apparatus that comprises, has,
includes, contains a list of elements does not include only those
elements but may include other elements not expressly listed or
inherent to such process, method, article, or apparatus. An element
proceeded by "comprises . . . a", "has . . . a", "includes . . .
a", "contains . . . a" does not, without more constraints, preclude
the existence of additional identical elements in the process,
method, article, or apparatus that comprises, has, includes,
contains the element. The terms "a" and "an" are defined as one or
more unless explicitly stated otherwise herein. The terms
"substantially", "essentially", "approximately", "about" or any
other version thereof, are defined as being close to as understood
by one of ordinary skill in the art, and in one non-limiting
embodiment the term is defined to be within 10%, in another
embodiment within 5%, in another embodiment within 1% and in
another embodiment within 0.5%. The term "coupled" as used herein
is defined as connected, although not necessarily directly and not
necessarily mechanically. A device or structure that is
"configured" in a certain way is configured in at least that way,
but may also be configured in ways that are not listed.
[0042] It will be appreciated that some embodiments may be
comprised of one or more generic or specialized processors (or
"processing devices") such as microprocessors, digital signal
processors, customized processors and field programmable gate
arrays (FPGAs) and unique stored program instructions (including
both software and firmware) that control the one or more processors
to implement, in conjunction with certain non-processor circuits,
some, most, or all of the functions of the method and/or apparatus
described herein. Alternatively, some or all functions could be
implemented by a state machine that has no stored program
instructions, or in one or more application specific integrated
circuits (ASICs), in which each function or some combinations of
certain of the functions are implemented as custom logic. Of
course, a combination of the two approaches could be used.
[0043] Moreover, an embodiment can be implemented as a
computer-readable storage medium having computer readable code
stored thereon for programming a computer (e.g., comprising a
processor) to perform a method as described and claimed herein.
Examples of such computer-readable storage mediums include, but are
not limited to, a hard disk, a CD-ROM, an optical storage device, a
magnetic storage device, a ROM (Read Only Memory), a PROM
(Programmable Read Only Memory), an EPROM (Erasable Programmable
Read Only Memory), an EEPROM (Electrically Erasable Programmable
Read Only Memory) and a Flash memory. Further, it is expected that
one of ordinary skill, notwithstanding possibly significant effort
and many design choices motivated by, for example, available time,
current technology, and economic considerations, when guided by the
concepts and principles disclosed herein will be readily capable of
generating such software instructions and programs and ICs with
minimal experimentation.
[0044] The Abstract of the Disclosure is provided to allow the
reader to quickly ascertain the nature of the technical disclosure.
It is submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims. In addition,
in the foregoing Detailed Description, it can be seen that various
features are grouped together in various embodiments for the
purpose of streamlining the disclosure. This method of disclosure
is not to be interpreted as reflecting an intention that the
claimed embodiments require more features than are expressly
recited in each claim. Rather, as the following claims reflect,
inventive subject matter lies in less than all features of a single
disclosed embodiment. Thus the following claims are hereby
incorporated into the Detailed Description, with each claim
standing on its own as a separately claimed subject matter.
* * * * *