U.S. patent application number 14/944429 was filed with the patent office on 2016-05-19 for wireless communication method and device.
The applicant listed for this patent is MediaTek Inc.. Invention is credited to Chi-Chen LEE, Shih-Chieh LIAO, Han-Chiang LIU.
Application Number | 20160142960 14/944429 |
Document ID | / |
Family ID | 55962973 |
Filed Date | 2016-05-19 |
United States Patent
Application |
20160142960 |
Kind Code |
A1 |
LIU; Han-Chiang ; et
al. |
May 19, 2016 |
WIRELESS COMMUNICATION METHOD AND DEVICE
Abstract
A wireless communication method and device are provided. The
wireless communication method includes the steps of receiving a
plurality of measurement results; determining whether a cell-change
event is triggered according to the measurement results;
calculating a reverse-direction criterion to determine whether a
ping-pong effect will occur when the cell-change event is
triggered; and terminating the cell-change event when the ping-pong
effect will occur.
Inventors: |
LIU; Han-Chiang; (Hsinchu
City, TW) ; LEE; Chi-Chen; (Taipei City, TW) ;
LIAO; Shih-Chieh; (Kaohsiung City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MediaTek Inc. |
Hsin-Chu |
|
TW |
|
|
Family ID: |
55962973 |
Appl. No.: |
14/944429 |
Filed: |
November 18, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62194368 |
Jul 20, 2015 |
|
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|
62081692 |
Nov 19, 2014 |
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Current U.S.
Class: |
455/436 |
Current CPC
Class: |
H04W 88/06 20130101;
H04W 36/0083 20130101; H04W 36/0061 20130101; H04W 36/30 20130101;
H04W 68/02 20130101; H04W 48/20 20130101; H04B 1/3816 20130101;
H04W 88/02 20130101 |
International
Class: |
H04W 36/30 20060101
H04W036/30; H04W 36/00 20060101 H04W036/00; H04W 24/10 20060101
H04W024/10 |
Claims
1. A wireless communication method, comprising: receiving a
plurality of measurement results; determining whether a cell-change
event is triggered according to the measurement results;
calculating a reverse-direction criterion to determine whether a
ping-pong effect will occur when the cell-change event is
triggered; and terminating the cell-change event when the ping-pong
effect will occur.
2. The wireless communication method of claim 1, wherein the
cell-change event is a cell reselection (CR) or a handover
(HO).
3. The wireless communication method of claim 2, further
comprising: checking whether the reverse-direction criterion is
satisfied according to stored system information or stored
measurement parameter to determine whether the ping-pong effect
will occur.
4. The wireless communication method of claim 2, further
comprising: removing a target cell or a target frequency for an
evaluation from a candidate cell list for a time period when the
reverse-direction criterion is satisfied.
5. The wireless communication method of claim 3, wherein if the
cell reselection is for inter radio access technology (IRAT), the
method further comprises: performing an evaluation for the cell
reselection in an evaluation phase before radio access technology
(RAT) changes, wherein system information for a target cell is
obtained in the evaluation phase.
6. The wireless communication method of claim 3, further
comprising: performing a cell global ID check or checks location
information or history information to avoid physical cell identity
(PCI) confusion.
7. The wireless communication method of claim 3, further
comprising: forbidding transmission of a measurement report for
triggering the handover to a target cell when the reverse-direction
criterion is satisfied.
8. The wireless communication method of claim 3, further
comprising: performing handover when the stored measurement
parameters for the target cell cannot be obtained.
9. The wireless communication method of claim 1, wherein if the
cell-change event is for inter radio access technology (IRAT), the
method further comprises: determining whether a current radio
access technology is a preferred radio access technology and
whether the current radio access technology has good signal
quality; and checking the reverse-direction criterion when the
current radio access technology is the preferred radio access
technology and the current radio access technology has good signal
quality.
10. The wireless communication method of claim 9, wherein when the
current radio access technology is not the preferred radio access
technology or the current radio access technology does not have
good signal quality, the reverse-direction criterion will not be
checked.
11. The wireless communication method of claim 1, wherein if the
cell-change event is for intra long term evolution (INTRA-LTE), the
method further comprises: selecting a cell which has better signal
strength to camp on when the ping-pong effect will occur.
12. The wireless communication method of claim 1, further
comprising: checking whether a multiple-cell ping-pong will occur
according to cell-change history information and stored system
information.
13. A wireless communication device, comprising: a processor,
configured to determine whether a cell-change event is triggered
according to measurement results, and calculate a reverse-direction
criterion to determine whether a ping-pong effect will occur when
the cell-change event is triggered, wherein the processor
terminates the cell-change event when the ping-pong effect will
occur.
14. The wireless communication device of claim 13, wherein the
cell-change event is a cell reselection (CR) or a handover
(HO).
15. The wireless communication device of claim 14, wherein the
processor further calculates whether the reverse-direction
criterion is satisfied according to stored system information or
stored measurement parameter to determine whether the ping-pong
effect will occur.
16. The wireless communication device of claim 14, wherein the
processor further removes a target cell or a target frequency for
an evaluation from a candidate cell list for a time period.
17. The wireless communication device of claim 15, wherein if the
cell reselection is for inter radio access technology (IRAT), the
processor further performs an evaluation for the cell reselection
in an evaluation phase before radio access technology (RAT)
changes, wherein system information for a target cell is obtained
in the evaluation phase.
18. The wireless communication device of claim 15, wherein the
processor further performs a cell global ID check or checks
location information or history information to avoid physical cell
identity (PCI) confusion.
19. The wireless communication device of claim 15, wherein the
processor further forbids the transmission of a measurement report
for triggering the handover to technology target cell when the
reverse-direction criterion is satisfied.
20. The wireless communication device of claim 15, wherein the
processor further performs handover when the stored measurement
parameters for the target cell cannot be obtained.
21. The wireless communication device of claim 13, wherein if the
cell-change event is for inter radio access technology (IRAT), the
processor further determines whether a current radio access
technology is a preferred radio access technology and whether the
current radio access technology has good signal quality, wherein
when the current radio access technology is the preferred radio
access technology and the current radio access technology has good
signal quality, the processor checks the reverse-direction
criterion.
22. The wireless communication device of claim 21, wherein when the
current radio access technology is not the preferred radio access
technology or the current radio access technology does not have
good signal quality, the processor will not check the
reverse-direction criterion.
23. The wireless communication device of claim 13, wherein if the
cell-change event is for intra long term evolution (INTRA-LTE), the
processor further selects a cell which has better signal strength
to camp on.
24. The wireless communication device of claim 13, wherein the
processor further checks whether a multiple-cell ping-pong will
occur according to cell-change history information and stored
system information.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This Application claims priority of U.S. Provisional Patent
Application No. 62/081,692, filed on Nov. 19, 2014 and Provisional
Patent Application No. 62/194,368, filed on Jul. 20, 2015, the
entirety of which is incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention generally relates to a wireless communication
technology, and more particularly, to a wireless communication
method for avoiding the ping-pong effect when cell reselection (CR)
or handover (HO) is triggered.
[0004] 2. Description of the Related Art
[0005] Wireless communication systems have been used widely to
provide various telecommunication services such as telephony,
video, data, messaging, and broadcast services. Typical wireless
communication systems may employ multiple-access technologies
capable of supporting communication with multiple users by sharing
available system resources (e.g., bandwidth, transmission power).
Examples of such multiple-access technologies 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,
single-carrier frequency divisional multiple access (SC-FDMA)
systems, and time division synchronous code division multiple
access (TD-SCDMA) systems.
[0006] These multiple access technologies have been adopted in
various telecommunication standards to provide a common protocol
that enables different wireless devices to communicate on a
municipal, national, regional, and even global level. An example of
an emerging telecommunication standard is Long Term Evolution
(LTE). LTE is a set of enhancements to the Universal Mobile
Telecommunications System (UMTS) mobile standard promulgated by the
Third Generation Partnership Project (3GPP). It is designed to
better support mobile broadband Internet access by improving
spectral efficiency, lowering costs, improving services, making use
of new spectrums, and integrating better with other open standards
using OFDMA on downlinks (DL), and SC-FDMA on uplinks (UL) and
multiple-input multiple-output (MIMO) antenna technology.
[0007] When user equipment (UE) needs to change a cell, the cell
reselection (CR) or handover (HO) procedure will be performed.
However, when the UE frequently switches serving cells between
multiple cells within a short period of time, a ping-pong effect
will occur. The ping-pong effect may result in excessive power
consumption and a poor user experience. Therefore, how to avoid the
ping-pong effect when the UE needs to change cells is a subject
worthy of discussion.
BRIEF SUMMARY OF THE INVENTION
[0008] A wireless communication method and device are provided to
overcome the problems mentioned above.
[0009] An embodiment of the invention provides a wireless
communication method. The wireless communication method comprises
the steps of receiving a plurality of measurement results;
determining whether a cell-change event is triggered according to
the measurement results; calculating a reverse-direction criterion
to determine whether a ping-pong effect will occur when the
cell-change event is triggered; and terminating the cell-change
event when the ping-pong effect will occur during the
reverse-direction.
[0010] An embodiment of the invention provides a wireless
communication device. The wireless communication device comprises a
processor. The processor is configured to determine whether a
cell-change event is triggered according to measurement results,
and calculate a reverse-direction criterion to determine whether a
ping-pong effect will occur when the cell-change event is
triggered, wherein the processor terminate the cell-change event
when the ping-pong effect will occur.
[0011] Other aspects and features of the invention will become
apparent to those with ordinary skill in the art upon review of the
following descriptions of specific embodiments of methods and
systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will become more fully understood by referring
to the following detailed description with reference to the
accompanying drawings, wherein:
[0013] FIG. 1 is a block diagram of a mobile communications system
100 according to an embodiment of the invention;
[0014] FIG. 2 is a schematic diagram illustrating the
reverse-direction criterion check for cell reselection for IRAT
according to an embodiment of the invention;
[0015] FIG. 3 is a schematic diagram illustrating the
reverse-direction criterion check for cell reselection for
INTRA-LTE according to an embodiment of the invention;
[0016] FIG. 4 is a schematic diagram illustrating the
reverse-direction criterion check for handover according to an
embodiment of the invention;
[0017] FIG. 5A is a schematic diagram illustrating the ping-pong
effect for multiple cells according to an embodiment of the
invention;
[0018] FIG. 5B is a schematic diagram illustrating the ping-pong
effect for multiple cells according to another embodiment of the
invention
[0019] FIGS. 6A-6B is a flow chart illustrating the wireless
communication method for cell reselection according to an
embodiment of the invention;
[0020] FIG. 7 is a flow chart illustrating the wireless
communication method for handover according to an embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The following description is of the best-contemplated mode
of carrying out the invention. This description is made for the
purpose of illustrating the general principles of the invention and
should not be taken in a limiting sense. The scope of the invention
is best determined by reference to the appended claims.
[0022] FIG. 1 is a block diagram of a mobile communications system
100 according to an embodiment of the invention. The system 100
comprises User Equipment (UE) 110 and a service network 120. The UE
110 may be a mobile communications device, such as a cellular
phone, a smartphone modem processor, a data card, a laptop stick, a
mobile hotspot, a USB modem, a tablet, etc.
[0023] The UE 110 may comprise at least a baseband signal
processing device 111, a radio frequency (RF) signal processing
device 112, a processor 113, a memory device 114, and an antenna
module comprising at least one antenna. Note that, in order to
clarify the concept of the invention, FIG. 1 presents a simplified
block diagram in which only the elements relevant to the invention
are shown. However, the invention should not be limited to what is
shown in FIG. 1.
[0024] The RF signal processing device 112 may receive RF signals
via the antenna and process the received RF signals to convert the
received RF signals to baseband signals to be processed by the
baseband signal processing device 111, or receive baseband signals
from the baseband signal processing device 111 and convert the
received baseband signals to RF signals to be transmitted to a peer
communications apparatus. The RF signal processing device 112 may
comprise a plurality of hardware elements to perform radio
frequency conversion. For example, the RF signal processing device
112 may comprise a power amplifier, a mixer, etc.
[0025] The baseband signal processing device 111 may further
process the baseband signals to obtain information or data
transmitted by the peer communications apparatus. The baseband
signal processing device 111 may also comprise a plurality of
hardware elements to perform baseband signal processing. The
baseband signal processing may comprise analog-to-digital
conversion (ADC)/digital-to-analog conversion (DAC), gain
adjustment, modulation/demodulation, encoding/decoding, and so
on.
[0026] The processor 113 may control the operations of the baseband
signal processing device 111 and the RF signal processing device
112. According to an embodiment of the invention, the processor 113
may also be arranged to execute the program codes of the software
module(s) of the corresponding baseband signal processing device
111 and/or the RF signal processing device 112. The program codes
accompanied by specific data in a data structure may also be
referred to as a processor logic unit or a stack instance when
being executed. Therefore, the processor 113 may be regarded as
being comprised of a plurality of processor logic units, each for
executing one or more specific functions or tasks of the
corresponding software module(s).
[0027] The memory device 114 may store the software and firmware
program codes, system data, user data, etc. of the UE 110. The
memory device 114 may be a volatile memory such as a Random Access
Memory (RAM); a non-volatile memory such as a flash memory or
Read-Only Memory (ROM); a hard disk; or any combination
thereof.
[0028] According to an embodiment of the invention, the RF signal
processing device 112 and the baseband signal processing device 111
may collectively be regarded as a radio module capable of
communicating with a wireless network to provide wireless
communications services in compliance with a predetermined Radio
Access Technology (RAT). Note that, in some embodiments of the
invention, the UE 110 may be extended further to comprise more than
one antenna and/or more than one radio module, and the invention
should not be limited to what is shown in FIG. 1.
[0029] In addition, in some embodiments of the invention, the
processor 113 may be configured inside of the baseband signal
processing device 111, or the UE 110 may comprise another processor
configured inside of the baseband signal processing device 111.
Thus the invention should not be limited to the architecture shown
in FIG. 1.
[0030] The service network 120 may comprise a GSM EDGE Radio Access
Network (GERAN) 130, a Universal Terrestrial Radio Access Network
(UTRAN) 140, an Evolved UTRAN (E-UTRAN) 150, a General Packet Radio
Service (GPRS) subsystem 160 and an Evolved Packet Core (EPC)
subsystem 170. The GERAN 130, UTRAN 140 and E-UTRAN 150 may be in
communication with the GPRS subsystem 160 or the EPC subsystem 170,
wherein the GERAN 130, UTRAN 140 and E-UTRAN 150 allow connectivity
between the UE 110 and the GPRS subsystem 160 or the EPC subsystem
170 by providing the functionality of wireless transmission and
reception to and from the UE 110 for the GPRS subsystem 160 or the
EPC subsystem 170, and the GPRS subsystem 160 or the EPC subsystem
170 signals the required operation to the GERAN 130, UTRAN 140 and
E-UTRAN 150 for providing wireless services to the UE 110. The
GERAN 130, UTRAN 140 and E-UTRAN 150 may contain one or more base
stations (or called NodeBs or eNodeBs) and Radio Network
Controllers (RNCs). Specifically, the GPRS subsystem 160 includes a
Serving GPRS (General Packet Radio Services) Support Node (SGSN)
161 and a Gateway GPRS Support Node (GGSN) 162, wherein the SGSN
161 is the key control node for packet routing and transfer,
mobility management (e.g., attach/detach and location management),
session management, logical link management, and authentication and
charging functions, etc., and the GGSN 162 is responsible for
Packet Data Protocol (PDP) address assignments and interoperability
with external networks. The EPC subsystem 170 may comprise a
Mobility Management Entity (MME) 171, which may be responsible for
idle mode UE tracking, paging procedures, and attachment and
activation processes. The EPC subsystem 170 may also comprise a
Servicing Gateway (SGW) 172, which may be responsible for the
routing and forwarding of data packets. The EPC subsystem 170 may
also include a Packet data network Gateway (PGW) 173, which may be
responsible for providing connectivity from the UE 110 to external
networks. Both the SGSN 161 and the MME 171 may be in communication
with Home Subscriber Server (HSS) 180 which may provide device
identification information, an International Mobile Subscriber
Identity (IMSI), etc. It should be appreciated that the EPC
subsystem 170 may also comprise a S4-SGSN 175, thereby allowing the
GERAN 130 or UTRAN 140 to be accessed when the GPRS subsystem 160
is replaced by the EPC subsystem 170. Additionally, the service
network 120 may also include other functional entities, such as a
Home Location Register (HLR) (not shown) which is a central
database storing user-related and subscription-related information,
and the invention is not limited thereto. In an embodiment of the
invention, the service network 120 may also comprise a Code
Division Multiple Access (CDMA) network.
[0031] In an embodiment of the invention, the processor 113 may
determine whether a cell-change event is triggered according to the
receiving measurement results of neighboring cells, wherein the
cell-change event may be cell reselection (CR) or handover (HO).
When the UE 110 is in an idle mode, the UE 110 may perform cell
reselection to change cell according the criteria provided by
system information. When the UE 110 in connected mode, the
cell-change is controlled by the network 120. Specifically, the UE
110 may transmit measurement report to the network 120 first. When
the network 120 receives the measurement report from UE 110, the
network 120 may determine whether to perform a handover according
to the measurement report. The measurement report may correspond to
a specific event, such as A3, B2, and A2. For general used case,
the event A3 is configured to trigger the LTE handover, event B2 is
configured to trigger the inter radio access technology (IRAT)
handover and event is A2 configured to trigger the redirection. It
is should be understood that the invention is not limited to above
specific events.
[0032] When the cell-change event is triggered, the processor 113
will perform a reverse-direction criterion calculation to check
whether a reverse-direction criterion satisfies a condition for
changing cells. Then, the processor 113 will determine whether a
ping-pong effect may occur according to the checking result. In an
embodiment of the invention, when the checking result indicates
that the reverse-direction criterion is satisfied for changing
cells, i.e. the cell-change event will also be triggered in the
reverse direction, the processor 113 determines that the ping-pong
effect will occur. When the checking result indicates that the
reverse-direction criterion is not satisfied for changing cells,
i.e. the cell-change event will not be triggered in reverse
direction, the processor 113 determines that the ping-pong effect
will not occur. The details are discussed below. In an embodiment
of the invention, when the processor 113 determines that the
ping-pong effect will occur, the processor 113 will terminate the
cell-change procedure (cell reselection or handover).
[0033] In an embodiment of the invention, for cases of cell
reselection (CR), the processor 113 checks whether the
reverse-direction criterion is satisfied for changing cells
according to the stored system information corresponding to a
target cell to determine whether the ping-pong effect will occur.
In an embodiment of the invention, for 4G radio access technology,
the necessary system information include
SystemInformationBlockType1 (SIB1), SystemInformationBlockType3
(SIB3), SystemInformationBlockType4 (SIB4),
SystemInformationBlockType5 (SIB5) for intra-LTE cell reselection,
and additional SystemInformationBlockType6 (SIB6),
SystemInformationBlockType7 (SIB7) is needed for inter radio access
technology (IRAT) cell reselection. In an embodiment of the
invention, for 3G radio access technology, the system information
can be Master Information Block (MIB) and
SystemInformationBlockType19 (SIB19). In an embodiment of the
invention, for 2G radio access technology, the system information
can be SI2Quater, SI3.
[0034] In an embodiment of the invention, the memory device 114 may
store the system information which the UE 110 has previously
collected, and the collected system information will be regarded as
the stored system information. In an embodiment of the invention,
when the processor 113 cannot obtain the stored system information
for the target cell, i.e. the memory device 114 does not have the
system information for the target cell, the processor 113 may
perform evaluation phase to get the system information for the
target cell in an evaluation phase before the cell reselection is
performed. The system information will be obtained in the
evaluation phase.
[0035] In an embodiment of the invention, the cell reselection is
for inter radio access technology (IRAT) cell change, i.e. the
current cell which the UE 110 is camping on and the target cell
corresponds to different radio access technologies. When the IRAT
cell reselection is triggered, the processor 113 may perform an
evaluation (i.e. in an evaluation phase) to prepare the cell
reselection before radio access technology (RAT) changes. Then, the
processor 113 may check whether the reverse-direction criterion is
satisfied according to the stored system information of the target
cell. If the reverse-direction criterion is satisfied for changing
cells, the processor 113 will terminate (or fail) the evaluation,
i.e. the radio access technology (RAT) will not change. If the
reverse-direction criterion is not satisfied for changing cells,
the IRAT cell resection procedure will continue.
[0036] In an embodiment of the invention, if the evaluation is
terminated because the reverse-direction criterion is satisfied for
changing cells, the processor 113 may remove the target cell or
target frequency for the evaluation from a candidate cell list for
a time period on the current radio access technology to avoid
retrying the target cell frequently. In an embodiment of the
invention, the processor 113 may initiate a timer that corresponds
to the time period. The target cell or the frequency for the
evaluation will not be used until the timer expires.
[0037] In an embodiment of the invention, when the ping-pong is
detected (i.e. the reverse-direction criterion is satisfied), the
processor 113 may keep the UE 110 in a preferred RAT. The preferred
RAT means the RAT with a higher priority. For example, if the RAT
for a 4G network has a higher priority than the RAT for a 3G
network, the RAT for 4G may regarded as the preferred RAT. When the
ping-pong is detected and the target RAT is the preferred RAT, the
processor 133 may still change the current RAT to the target RAT.
Therefore, in an embodiment of the invention, if the cell
reselection is for inter radio access technology (IRAT), the
processor 113 may determine whether the current RAT is a preferred
RAT and whether the current RAT has good signal quality first. Only
when the current RAT is the preferred RAT and the current RAT has
good signal quality, will the processor 113 check the
reverse-direction criterion. When the current RAT is not the
preferred RAT or the current RAT does not have good signal quality,
the processor 113 will not check the reverse-direction
criterion.
[0038] FIG. 2 is a schematic diagram illustrating the
reverse-direction criterion check for IRAT cell reselection
according to an embodiment of the invention. As shown in FIG. 2,
the current radio access technology (current RAT) is LTE (4G) and
the target radio access technology (target RAT) is UMTS (3G). When
a cell reselection procedure from 4G to 3G is triggered, in the
evaluation phase, the processor 113 may transmit a 4G3 IRCR
evaluation Request message from the current RAT to the target RAT.
Then, in the target RAT, the processor 113 may check whether the
reverse direction (from 3G to 4G) criterion is satisfied for
changing cells according to the stored system information for the
target cell of the target RAT. When the reverse-direction criterion
is satisfied for changing cells, the processor 113 will determine
that the ping-pong effect will occur (i.e. the ping-pong is
detected) and terminate (or fail) the evaluation. Then, the
processor 113 may transmit a 4G3 IRCR evaluation Cnf message from
the target RAT to the current RAT to notify the current RAT that
the evaluation has failed. When the current RAT obtains the 4G3
IRCR evaluation Cnf message, the processor 113 will remove the
target cell or the target frequency for the evaluation form a
candidate cell list for a time period.
[0039] In another embodiment of the invention, the cell reselection
is for intra long term evolution (INTRA-LTE), i.e. the target cell
and current cell are for the same radio access technology (i.e.
LTE). If the cell reselection for intra long term evolution is
triggered, when the target cell satisfies a cell-reselection
criterion (i.e. the target cell's signal strength and quality meets
the cell-reselection criterion), the processor 113 may check
whether the reverse-direction criterion is satisfied according to
the stored system information to determine whether the ping-pong
effect will occur. When the reverse-direction criterion is
satisfied, the processor 113 may remove the target cell from a
candidate cell list.
[0040] In an embodiment of the invention, if the cell reselection
is for intra long term evolution (INTRA-LTE), the processor 113 may
select a cell which has better signal strength to camp on when
processor 113 determines that the ping-pong effect will occur.
[0041] FIG. 3 is a schematic diagram illustrating the
reverse-direction criterion check for cell reselection for
INTRA-LTE according to an embodiment of the invention. As shown in
FIG. 3, the current cell is the LTE cell A and the target cell is
the LTE cell B. When the processor 113 receives the measurement
result of the LTE cell B, the processor 113 will determine whether
the INTRA-LTE cell reselection is triggered. If it is triggered,
the processor 113 will check whether the reverse-direction
criterion satisfies the condition according to the stored system
information to determine whether the ping-pong effect will occur.
When the reverse-direction criterion is satisfied, the processor
113 may determine the ping-pong effect will occur (i.e. the
ping-pong is detected) and remove the LTE cell B from a candidate
cell list. In an embodiment of the invention, the processor 113 may
select a cell which has better signal strength to camp on when the
ping-pong effect will occur.
[0042] In an embodiment of the invention, for cases of cell
reselection, the processor 113 may perform a cell global ID check
in the evaluation phase to avoid any physical cell identity (PCI)
confusion. For INTRA-LTE, the processor 113 can obtain the cell
global ID of the target cell from the SystemInformationBlockType1
(SIB 1). For 4G to 3G cell reselection, the processor 113 can
obtain the cell global ID of the target cell from the MIB. For 4G
to 2G cell reselection, the processor 113 can obtain the cell
global ID of the target cell from the SI3. The processor can
confirm whether the ID information of the target cell from the
stored information is the same as the cell global ID of the target.
In another embodiment of the invention, the processor 113 may check
location information to avoid PCI confusion. The location
information may be tracking area code (TAC) information, location
area code (LAC) information, routing area code (RAC) information,
and global positioning system (GPS) information. In another
embodiment of the invention, the processor 113 may check history
information to avoid PCI confusion.
[0043] In an embodiment of the in invention, for cases of handover
(HO), the processor 113 may check whether the reverse-direction
criterion is satisfied for changing cells according to stored
measurement parameters from a target cell to determine whether the
ping-pong effect will occur. If the reverse-direction criterion is
satisfied for changing cells, the processor 113 will determine that
the ping-pong effect will occur.
[0044] In an embodiment of the invention, if the handover is for
inter radio access technology (IRAT), the processor 113 may check
whether the reverse-direction criterion is satisfied according to
the stored measurement parameters from the target cell before a
measurement report (e.g. event B2) for triggering the handover is
transmitted from the UE 110 to a network of a current radio access
technology. That is to say, the check of the reverse-direction
criterion is performed before the measurement report is transmitted
from UE 110 to the network of the current radio access technology
to trigger the handover. When the reverse-direction criterion is
satisfied, the processor 113 may forbid the transmission of the
measurement report to the network of the current radio access
technology.
[0045] In an embodiment of the invention, if the memory device does
not store the stored measurement parameters for the target cell,
the processor 113 may continue the handover procedure (i.e.
transmit the measurement report to the network).
[0046] In an embodiment of the invention, when the ping-pong is
detected (i.e. the reverse-direction criterion is satisfied), the
processor 113 may keep the UE 110 in a preferred RAT. The preferred
RAT means the RAT with a higher priority. For example, if the RAT
for the 4G network has a higher priority than the RAT for the 3G
network, the RAT for 4G may regarded as the preferred RAT. When the
ping-pong is detected and the target RAT is the preferred RAT, the
processor 133 may still change the current RAT to the target RAT.
Therefore, in an embodiment of the invention, if the handover is
for inter radio access technology (IRAT), the processor 113 may
first determine whether the current RAT is a preferred RAT and
whether the current RAT has good signal quality. Only when the
current RAT is the preferred RAT and the current RAT has good
signal quality will the processor 113 check the reverse-direction
criterion. When the current RAT is not the preferred RAT or the
current RAT does not have good signal quality, the processor 113
will not check the reverse-direction criterion.
[0047] In an embodiment of the invention, if the handover is for
intra long term evolution (INTRA-LTE), the processor 113 may check
whether the reverse-direction criterion is satisfied according to
the stored measurement parameters for the target cell before a
measurement report for triggering the handover is transmitted to
the network of a current radio access technology. When the
reverse-direction criterion is satisfied, the processor 113 may
forbid the transmission of the measurement report to the network of
the current radio access technology.
[0048] In an embodiment of the invention, if the cell handover is
for intra long term evolution (INTRA-LTE), the processor 113 may
select a cell which has better signal strength to camp on when the
processor 113 determines that the ping-pong effect will occur.
[0049] FIG. 4 is a schematic diagram illustrating the
reverse-direction criterion check for handover according to an
embodiment of the invention. As shown in FIG. 4, the current cell
is the LTE cell A and the target cell is the cell B where the LTE
cell A and the cell B may correspond to the same RAT (INTRA-LTE) or
different RATs (IRAT). When the processor 113 receives the
measurement result from the cell B, the processor 113 will
determine whether the measurement report for INTRA-LTE or IRAT is
triggered. If the measurement report for INTRA-LTE or IRAT is
triggered, the processor 113 will check whether the
reverse-direction criterion is satisfied according to the
measurement parameters from the cell B to determine whether the
ping-pong effect will occur. When the reverse-direction criterion
is satisfied, the processor 113 may determine the ping-pong effect
will occur and forbid the transmission of the measurement report
(HO event report) to the network.
[0050] Because the ping-pong effect may be more complex, such as
the ping-pong effect taking place between more than two cells. For
example, as shown in FIG. 5A, the ping-pong effect does not occur
between the 4G cell 1 and 4G cell 2, between the 4G cell 2 and 4G
cell 3, and between the 4G cell 3 and 4G cell 1. However, the
ping-pong effect will occur every three 4G cells. For another
example, as shown in FIG. 5B, the ping-pong effect does not occur
between the 4G cell 1 and 3G cell 1, between the 3G cell 1 and 4G
cell 3, and between the 4G cell 3 and 4G cell 1. However, the
ping-pong effect will occur every three 4G cells. Therefore, in an
embodiment of the invention, when the processor 133 determine the
pin-pong effect will not occur between two cells, the processor 133
may further check whether a multiple-cell ping-pong (not limited to
three cells) will occur according to cell-change history
information and stored system information.
[0051] FIGS. 6A-6B is a flow chart illustrating the wireless
communication method for cell reselection according to an
embodiment of the invention. The wireless communication method is
applied to the UE 110. First, in step S610, the UE 110 receives a
plurality of measurement results from neighboring cells. In step
S620, the UE 110 may determine whether the cell reselection is
triggered according to the measurement results. If the UE 110
determines that cell reselection is not triggered according to the
measurement results, the method returns to step S620. If the UE 110
determines that cell reselection is triggered according to the
measurement results, step S630 will be performed. In step S630, the
UE 110 may determine whether the stored system information can be
obtained.
[0052] If the stored system information can be obtained, step S640
will be performed. In step S640, the UE 110 may determine whether
there is any related information to avoid any physical cell
identity (PCI) confusion. If related information to avoid PCI
confusion can be obtained, the UE 110 may perform a cell global ID
check or check location information or history information to avoid
PCI confusion (step S650). If related information to avoid PCI
confusion cannot be obtained, step S660 may be performed. In step
S660, the processor 113 may perform an evaluation (i.e. in
evaluation phase) before the cell reselection is executed, wherein
system information (comprising the related information to avoid PCI
confusion) for a target cell will be obtained in the evaluation
phase. If the stored system information cannot be obtained, the
processor will also perform step S660.
[0053] Then, in step S670, the UE 110 may calculate a
reverse-direction criterion to determine whether a ping-pong effect
will occur. When the reverse-direction criterion is satisfied, the
UE 110 will determine that the ping-pong effect will occur. When
the UE 110 determines that the ping-pong effect will occur, step
S680 will be performed. In step S680, the UE 110 may determine not
to perform the cell reselection.
[0054] When the reverse-direction criterion is not satisfied, the
UE 110 will further determine whether the ping-pong effect for
multiple cells will occur according to the cell change history
information (S690). If the ping-pong effect for multiple cells will
occur, the UE 110 will not perform the cell reselection (S680). If
the ping-pong effect for multiple cells will not occur, the UE 110
will continue to perform cell reselection (step S6100). In an
embodiment of the invention, if the UE 110 cannot obtain the cell
change history information in step S690, the UE will perform cell
reselection (S6100).
[0055] FIG. 7 is a flow chart illustrating the wireless
communication method for handover according to an embodiment of the
invention. The wireless communication method is applied to the UE
110. First, in step S710, the UE 110 receives a plurality of
measurement results from neighboring cells. In step S720, the UE
110 may determine whether the handover is triggered according to
the measurement results. If the UE 110 determines that handover is
not triggered according to the measurement results, the method
returns to step S720. If the UE 110 determines that handover is
triggered according to the measurement results, step S730 will be
performed. In step S730, the UE 110 may determine whether the
stored measurement parameters for the target cell can be
obtained.
[0056] If the stored system information can be obtained, step S740
will be performed. In step S740, the UE 110 may calculate a
reverse-direction criterion to determine whether a ping-pong effect
will occur. When the reverse-direction criterion is satisfied, the
UE 110 will determine that the ping-pong effect will occur. When
the UE 110 determines that the ping-pong effect will occur, step
S750 will be performed. In step S750, the UE 110 may determine not
to transmit the measurement report to the network to trigger the
handover. If the stored measurement parameter cannot be obtained,
step S760 will be performed. In step S760, the UE 110 will transmit
the measurement report to the network to trigger the handover.
[0057] When the reverse-direction criterion is not satisfied for
changing cells, the UE 110 will further determine whether the
ping-pong effect for multiple cells will occur according to the
cell change history information (S770). If the ping-pong effect for
multiple cells will occur, the UE 110 will perform step 750. If the
ping-pong effect for multiple cells will not occur, the UE 110 will
continue to perform step S760.
[0058] In the wireless communication method of the invention, the
ping-pong effect can be avoided by the reverse-direction criterion
check.
[0059] The steps of the method described in connection with the
aspects disclosed herein may be embodied directly in hardware, in a
software module executed by a processor, or in a combination of the
two. A software module (e.g., including executable instructions and
related data) and other data may reside in a data memory such as
RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory,
registers, a hard disk, a removable disk, a CD-ROM, or any other
form of computer-readable storage medium known in the art. A sample
storage medium may be coupled to a machine such as, for example, a
computer/processor (which may be referred to herein, for
convenience, as a "processor") such that the processor can read
information (e.g., code) from and write information to the storage
medium. A sample storage medium may be integral to the processor.
The processor and the storage medium may reside in an ASIC. The
ASIC may reside in user equipment. In the alternative, the
processor and the storage medium may reside as discrete components
in user equipment. Moreover, in some aspects, any suitable
computer-program product may comprise a computer-readable medium
comprising codes relating to one or more of the aspects of the
disclosure. In some aspects, a computer software product may
comprise packaging materials.
[0060] It should be noted that although not explicitly specified,
one or more steps of the methods described herein can include a
step for storing, displaying and/or outputting as required for a
particular application. In other words, any data, records, fields,
and/or intermediate results discussed in the methods can be stored,
displayed, and/or output to another device as required for a
particular application. While the foregoing is directed to
embodiments of the present invention, other and further embodiments
of the invention can be devised without departing from the basic
scope thereof. Various embodiments presented herein, or portions
thereof, can be combined to create further embodiments. The above
description is of the best-contemplated mode of carrying out the
invention. This description is made for the purpose of illustrating
the general principles of the invention and should not be taken in
a limiting sense. The scope of the invention is best determined by
reference to the appended claims.
[0061] The above paragraphs describe many aspects. Obviously, the
teaching of the invention can be accomplished by many methods, and
any specific configurations or functions in the disclosed
embodiments only present a representative condition. Those who are
skilled in this technology can understand that all of the disclosed
aspects in the invention can be applied independently or be
incorporated.
[0062] While the invention has been described by way of example and
in terms of preferred embodiment, it is to be understood that the
invention is not limited thereto. Those who are skilled in this
technology can still make various alterations and modifications
without departing from the scope and spirit of this invention.
Therefore, the scope of the present invention shall be defined and
protected by the following claims and their equivalents.
* * * * *