U.S. patent application number 17/840778 was filed with the patent office on 2022-09-29 for optimized detection of unnecessary inter-rat handover.
The applicant listed for this patent is Telefonaktiebolaget LM Ericsson (publ). Invention is credited to Angelo Centonza, Stefan Engstrom, Claes-Goran Persson, Paul Schliwa-Bertling.
Application Number | 20220312231 17/840778 |
Document ID | / |
Family ID | 1000006405847 |
Filed Date | 2022-09-29 |
United States Patent
Application |
20220312231 |
Kind Code |
A1 |
Centonza; Angelo ; et
al. |
September 29, 2022 |
Optimized Detection of Unnecessary Inter-RAT Handover
Abstract
According to an aspect, a network node operating in a first RAN
according to a first RAT is the target of an inter-RAT (IRAT)
handover. The network node receives a handover request for a user
equipment from a cell in a second RAN operating according to a
second RAT. After handover of the user equipment to a cell in the
first RAN is completed, the network node configures the user
equipment to measure one or more frequencies corresponding to the
second RAN. Based on measurements reported by the user equipment
for the one or more frequencies, the network node identifies one or
more detected cells exceeding a measurement threshold, and sends a
handover report towards the second RAN. The handover report
includes, for at least one detected cell exceeding the measurement
threshold, a physical cell identifier for the detected cell and a
frequency identifier for the detected cell.
Inventors: |
Centonza; Angelo;
(Torrenueva Costa, ES) ; Engstrom; Stefan;
(Linkoping, SE) ; Persson; Claes-Goran; (Mjolby,
SE) ; Schliwa-Bertling; Paul; (Ljungsbro,
SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget LM Ericsson (publ) |
Stockholm |
|
SE |
|
|
Family ID: |
1000006405847 |
Appl. No.: |
17/840778 |
Filed: |
June 15, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14888650 |
Nov 2, 2015 |
11395157 |
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PCT/SE2015/051050 |
Oct 5, 2015 |
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17840778 |
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62076856 |
Nov 7, 2014 |
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62076941 |
Nov 7, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 36/0061 20130101;
H04W 36/14 20130101; H04W 36/0094 20130101; H04W 36/0066 20130101;
H04W 36/0088 20130101; H04W 36/0085 20180801; H04W 24/02 20130101;
H04W 36/00837 20180801 |
International
Class: |
H04W 24/02 20060101
H04W024/02; H04W 36/00 20060101 H04W036/00; H04W 36/14 20060101
H04W036/14 |
Claims
1. A method, in a network node operating in a first radio access
network (RAN) according to a first radio access technology (RAT),
the method comprising: after handover of a user equipment from a
cell in a second RAN to a cell in the first RAN is completed,
configuring the user equipment to measure one or more frequencies
corresponding to the second RAN; sending a handover report towards
the second RAN, the handover report comprising, for at least cell
for which measurement results reported by the user equipment exceed
a measurement threshold, a physical cell identifier for the cell
and a frequency identifier for the cell.
2. The method of claim 1, wherein the second RAN operates according
to a second RAT, differing from the first RAT.
3. The method of claim 1, further comprising receiving information
identifying the one or more frequencies corresponding to the second
RAN in a message associated with a handover request.
4. The method of claim 3, wherein the information identifying the
one or more frequencies comprises an Evolved Universal Terrestrial
Radio Access (E-UTRA) Absolute Radio-Frequency Channel Number
(EARFCN).
5. The method of claim 3, further comprising receiving, in a
message associated with the handover request, measurement
information indicating, for at least one of the one or more
frequencies, whether or not the user equipment should measure
closed-subscriber-group (CSG) cells corresponding to the at least
one of the one or more frequencies, wherein said configuring the
user equipment to measure one or more frequencies corresponding to
the second RAN comprises configuring the user equipment to measure
CSG cells or not to measure CSG cells, according to the received
measurement information.
6. The method of claim 5, wherein the measurement information is a
single indicator indicating whether or not the user equipment
should measure CSG cells for all of the one or more
frequencies.
7. The method of claim 5, wherein the measurement information
comprises a separate indicator for each of the one or more
frequencies.
8. The method of claim 1, further comprising receiving information
identifying the measurement threshold in a message associated with
a handover request.
9. The method of claim 1, wherein the handover report includes, for
at least one of the identified detected cells, a global cell
identifier.
10. The method of claim 1, further comprising including, in the
handover report, a physical cell identifier and frequency
identifier only for cells for which a global cell identifier could
not be derived from measurements reported by the user
equipment.
11. The method of claim 1, wherein the first RAT is Global System
for Mobile Communications (GSM), Edge Radio Access Network (GERAN),
or UTRA, and the second RAT is E-UTRA.
12. A method, in a network node operating in a first radio access
network (RAN) according to a first radio access technology (RAT),
the method comprising: after handover of a user equipment from a
cell in the first RAN to a cell in a second RAN is completed,
receiving a handover report from the second RAN, the handover
report comprising, for at least one cell detected by the user
equipment, a physical cell identifier for the detected cell and a
frequency identifier for the detected cell; identifying a global
cell identifier for the at least one cell, based on the physical
cell identifier and frequency identifier; and adjusting one or more
mobility settings with respect to the at least one cell, in
response to receiving the handover report.
13. The method of claim 12, wherein the second RAN operates
according to a second RAT, differing from the first RAT.
14. The method of claim 12, further comprising sending, towards the
second RAN, information identifying one or more frequencies to be
measured by the user equipment, in a message associated with a
handover-required indication.
15. The method of claim 14, wherein the information identifying the
one or more frequencies comprises an Evolved Universal Terrestrial
Radio Access (E-UTRA) Absolute Radio-Frequency Channel Number
(EARFCN).
16. The method of claim 12, further comprising sending, in a
message associated with 1 handover-required indication, measurement
information indicating, for at least one of the one or more
frequencies, whether or not the user equipment should measure
closed-subscriber-group (CSG) cells corresponding to the at least
one of the one or more frequencies.
17. The method of claim 16, wherein the measurement information is
a single indicator indicating whether or not the user equipment
should measure CSG cells for all of the one or more
frequencies.
18. The method of claim 16, wherein the measurement information
comprises a separate indicator for each of the one or more
frequencies.
19. The method of claim 12, further comprising sending information
identifying a measurement threshold in a message associated with a
handover-required indication.
20. The method of claim 12, wherein the first RAT is Evolved
Universal Terrestrial Radio Access (E-UTRA) and the second RAT is
Global System for Mobile Communications (GSM), Edge Radio Access
Network (GERAN), or UTRA.
21. A network node apparatus adapted to operate in a first radio
access network (RAN) according to a first radio access technology
(RAT), the network node apparatus comprising a processing circuit
configured to: configure a user equipment to measure one or more
frequencies corresponding to a second RAN after handover of the
user equipment from a cell in the second RAN to a cell in the first
RAN is completed; and send a handover report towards the second
RAN, the handover report comprising, for at least cell for which
measurement results reported by the user equipment exceed a
measurement threshold, a physical cell identifier for the cell and
a frequency identifier for the cell.
22. A network node apparatus adapted to operate in a first radio
access network (RAN) according to a first radio access technology
(RAT), the network node apparatus comprising a processing circuit
configured to: receive a handover report from a second RAN, after
handover of a user equipment from a cell in the first RAN to a cell
in the second RAN is completed, the handover report comprising, for
at least one cell detected by the user equipment, a physical cell
identifier for the detected cell and a frequency identifier for the
detected cell; identify a global cell identifier for the at least
one cell, based on the physical cell identifier and frequency
identifier; and adjusting one or more mobility settings with
respect to the at least one cell, in response to receiving the
handover report.
Description
TECHNICAL FIELD
[0001] The technology disclosed herein relates generally to
wireless communication networks, and more particularly relates to
techniques for reducing unnecessary handovers from one radio access
technology to another.
BACKGROUND
[0002] Wireless phones and other user equipment supporting a
fourth-generation (4G) wireless technology such as the Long Term
Evolution (LTE) technology, formally known as Evolved Universal
Terrestrial Radio Access (E-UTRA), typically also support a 3G
technology, such as the Universal Terrestrial Radio Access (UTRA)
technology often referred to as Wideband Code-Division Multiple
Access (WCDMA). These same devices might also be compatible with 2G
networks, such as the Global System for Mobile Communications
(GSM)/EDGE Radio Access Network (GERAN).
[0003] These networks may be connected to one another and, in some
circumstances, may permit a user equipment (UE) to be handed over
from one to another. As shown in FIG. 1, the LTE and GERAN/UTRAN
architectures are combined by means of interfaces between the core
network nodes of each respective technology. See "General Packet
Radio Service (GPRS) enhancements for Evolved Universal Terrestrial
Radio Access Network (E-UTRAN) access," 3GPP TS 23.401, ver. 13.0.0
(September 2014), available at www.3gpp.org. These core nodes
include, for example, the Mobility Management Entity (MME), the
Serving GPRS Support Node (SGSN), the Serving Gateway (SGW), and
the Home Subscriber Server (HSS), all of whose functions are well
known to those generally familiar with the family of network
standards developed by members of the 3.sup.rd-Generation
Partnership Project (3GPP).
[0004] One of the ways for the LTE and GERAN/UTRAN technologies to
communicate with each other is via the RAN Information Management
(RIM) protocol, which allows transferring of information from LTE
to GERAN/UTRAN and vice-versa in a pre-configured manner. The RIM
protocol is specified in "3.sup.rd Generation Partnership Project;
Technical Specification Group GSM/EDGE Radio Access Network;
General Packet Radio Service (GPRS); Base Station System
(BSS)--Serving GPRS Support Node (SGSN); BSS GPRS Protocol (BSSGP)
(Release 12)," 3GPP TS 48.018, v. 12.3.0 (September 2014), also
available at www.3gpp.org.
[0005] In the current specifications, a specific type of RIM
interaction is defined for the purpose of avoiding unnecessary
handovers from LTE to GERAN/UTRAN networks. This interaction is
known as "Unnecessary IRAT Handover detection."
[0006] FIG. 2 shows a message sequence chart for the Unnecessary
Inter Radio Access Technology (IRAT) Handover detection procedure,
as per the current standards, where the target RAT is GERAN. A
similar message sequence is also valid when the target RAT is
UTRAN.
[0007] The operations illustrated in FIG. 2 are described in detail
in 3GPP TS 48.018 (cited above), 3GPP TS 36.413 (Release 12), 3GPP
TS 25.413 (Release 12), and 3GPP TS 48.008 (Release 12), all of
which can be found at www.3gpp.org. The illustrated procedure
allows the LTE radio access network (RAN) to configure specific
measurement criteria and thresholds for a UE that is handed over
from LTE to GERAN/UTRAN. More generally, similar procedures may be
used when a UE is handed over from a first RAN 204, operating
according to a first RAT, to a second RAN 202, operating according
to a second RAT.
[0008] Referring again to FIG. 2, the measurement configuration
sent from the source RAN/RAT (an LTE network, in this case) to the
target RAN/RAT (a GERAN/UTRAN network), is captured in the
information elements that make up the IRAT Measurement
Configuration IE. Details of the IRAT Measurement Configuration IE
can be found in 3GPP TS 48.018, 3GPP TS 25.413, and 3GPP TS 48.008;
some of those details are illustrated below, in FIGS. 3 and 4. FIG.
3 shows an IRAT Measurement Configuration Information Element (IE).
FIG. 4 a structure of an IRAT Measurement Configuration IE as used
for handover from LTE to UTRAN. The configuration of FIG. 4 may be
sent by LTE to UTRAN/GERAN via the Source BSS to Target BSS
Transparent Container IE or Old BSS to New BSS information IE (in
case of handover to GERAN; see 3GPP TS 48.018 and 3GPP TS 48.008)
or via the Source RNC to Target RNC Transparent Container IE (in
case of handover to UTRAN, see 3GPP TS 25.413) within the handover
signalling, i.e. as part of the HANDOVER REQUIRED and HANDOVER
REQUEST messages generated in LTE (as shown in step 1 and step 2 of
FIG. 2).
[0009] Upon reception of such configuration, the UTRAN/GERAN will
need to configure the UE (handed over from LTE) to perform
measurements for a time duration equal to the Measurement Duration
IE and over the E-UTRAN frequencies indicated in the E-UTRA
Absolute Radio-Frequency Channel Number (E-ARFCN) IE. The LTE cells
for which measurements are taken will be recorded by the target
UTRAN/GERAN base station if the measurement results are above
preconfigured thresholds specified in the REPORTING_THRESHOLD IE or
Reference Signal Received Power (RSRP) IE or Reference Signal
Receive Quality (RSRQ) IE.
[0010] The measurements performed by the UE as a result of the
Unnecessary IRAT Handover procedure will trigger the delivery of an
HO Report IE from GERAN/UTRAN to E-UTRAN as part of a RIM message
(see step 5 of FIG. 2) if the following is satisfied (excerpt from
3GPP TS 25.413 showing the conditions in UTRAN): [0011] HO Report
should be sent if there is either a single source RAT cell whose
measurement results exceed the threshold for the whole measurement
duration, or a group of source RAT cells together provide such
coverage. The cells that exceed the threshold in the first UE
measurement report are included in the HO Report. If both
thresholds are present, the received radio measurements must exceed
both the RSRP and the RSRQ thresholds in order to satisfy the
indicated radio conditions. [0012] When the HO Report is sent from
RNC at the end of the configured measurement duration, it shall set
the HO Report Type IE to "Unnecessary HO to another RAT". If the
measurement period expires due to an inter-RAT handover towards LTE
executed within the configured measurement duration, the RNC shall
set the HO Report Type IE in the HO Report to "Early IRAT
Handover". [0013] No HO Report shall be sent in case no E-UTRAN
cell could be included, or if the indicated period of time is
interrupted by an inter-RAT handover to a RAT different than LTE or
by an intra-UMTS handover with SRNC relocation.
[0014] As can be seen from the quote above, the HO Report IE will
be generated only if there are detected cells that satisfy the
measurement configuration criteria. Cells can be included in the HO
Report only if reported UE measurements for each of the cells
detected satisfy the configured thresholds for the whole duration
of the configured measurement window or for part of such duration,
in the event that the measurement window time is interrupted by an
inter-RAT handover towards LTE.
[0015] In case all the conditions are satisfied, the HO Report IE
sent from UTRAN/GERAN to LTE via RIM is constructed as shown in
FIG. 5 (see 3GPP TS 36.413). In the HO Report IE, the cells
reported in the Candidate Cell List IE are those LTE cells
providing good enough coverage, namely fulfilling the criteria
specified in the IRAT Measurement Configuration IE (see FIGS. 3 and
4). Such cells are represented by a list of E-UTRAN Cell Global
Identities (E-CGIs). The latter can be seen from the specifications
of the Candidate Cell ID IE, which is detailed as shown in FIGS. 6
and 7 (see 3GPP TS 36.413).
[0016] The discussion presented herein generally assumes a
management system having an arrangement like that shown in FIG. 8.
In this arrangement, node elements (NE), also referred to as eNodeB
s, are managed by a domain manager (DM), also referred to as the
operation and support system (OSS). A DM may further be managed by
a network manager (NM). The system composed by the DM and NM may be
referred as the Operation and Maintenance System (OAM). Two NEs are
interfaced by X2, whereas the interface between two DMs is referred
to as Itf-P2P. It is further assumed, in the discussion that
follows, that a function that automatically optimizes NE parameters
can, in principle, execute in the NE, DM, or NM.
SUMMARY
[0017] To unambiguously identify measured cells, the network node
in a target RAT providing a Handover Report to the source RAT
according to the techniques discussed above can use a global cell
identifier (such as the E-UTRAN Cell Global Identifier or ECGI)
that could identify each cell. However, this would require that
each potential target node (e.g., each base station) be provided in
advance with information sufficient to identify the cell from the
non-global information that is typically available from monitoring
the cell itself, such as the Physical Cell Identifier (PCI). This
pre-configuration of all target nodes with this information is
undesirable.
[0018] Embodiments of the presently disclosed techniques and
apparatus address this and other problems. In some embodiments, in
the case that the target Inter RAT node is not configured with the
mapping between PCI and frequency and the cell's ECGI, given that a
UE both in UTRAN and in GERAN reports a PCI and a frequency
indication for a detected LTE cell, then both the PCI and the
detected cell's frequency should be included in an opportune list
in the HO Report IE, to assist the target eNB in unequivocally
identifying the cell that was detected and reported by the UE. The
embodiments described below provide for adding PCI and frequency
information for cells fulfilling the Unnecessary IRAT Handover
Detection criteria to the existing HO Report IE.
[0019] To further specify the measurements expected from the
Unnecessary IRAT Handover Detection procedure, and by that
potentially limit the number of measurements performed by the UE
while served in GERAN, some extra information related to each
individual E-UTRAN frequency in the IRAT Measurement Configuration
IE could be supplied by the source eNB. This extra information
could, for, example consist of an indicator for each individual
E-UTRAN frequency, informing the BSS whether the UE (handed over
from LTE) shall be configured for measurements of (1) E-UTRAN macro
neighbor cells only, or (2) E-UTRAN CSG cells only, or (3) possibly
both cell types for the indicated E-UTRAN frequency. As an
alternative to a frequency-specific indicator, a common indicator
valid for all E-UTRAN frequencies included in the IRAT Measurement
Configuration IE could be supplied by the source eNB.
[0020] An example method according to some embodiments is suitable
for implementation in a network node operating in a first RAN
according to a first RAT. In this case, the network node is the
target of an IRAT handover. The method includes receiving a
handover request for a user equipment from a cell in a second RAN
operating according to a second RAT and, after handover of the user
equipment to a cell in the first RAN is completed, configuring the
user equipment to measure one or more frequencies corresponding to
the second RAN. Based on measurements reported by the user
equipment for the one or more frequencies, the network node
identifies one or more detected cells exceeding a measurement
threshold, and sends a handover report towards the second RAN. The
handover report includes, for at least one detected cell exceeding
the measurement threshold, a physical cell identifier for the
detected cell and a frequency identifier for the detected cell.
[0021] In some embodiments, the network node receives information
identifying the one or more frequencies corresponding to the second
RAN in a message associated with the handover request. In some of
these embodiments, the information identifying the one or more
frequencies comprises an E-UTRA Absolute Radio-Frequency Channel
Number (EARFCN). In some embodiments, the network node also
receives, in a message associated with the handover request,
measurement information indicating, for at least one of the one or
more frequencies, whether or not the user equipment should measure
closed-subscriber-group (CSG) cells corresponding to the at least
one of the one or more frequencies. In these embodiments,
configuring the user equipment to measure one or more frequencies
corresponding to the second RAN comprises configuring the user
equipment to measure CSG cells or not to measure CSG cells,
according to the received measurement information. The measurement
indicator in some of these embodiments may be a single indicator
indicating whether or not the user equipment should measure CSG
cells for all of the one or more frequencies. In others of these
embodiments, a separate indicator is provided for each of the one
or more frequencies.
[0022] In some embodiments, the handover report includes, for at
least one of the detected cells exceeding the measurement
threshold, a global cell identifier. In some embodiments, a
physical cell identifier and frequency identifier is included only
for those detected cells for which a global cell identifier is not
known or could not be derived from the measurements reported by the
user equipment. As shown by the embodiments, the first and second
RATs may be different RATs.
[0023] Another example method according to the present techniques
is carried out in a network node operating in a first RAN according
to a first RAT. In this case, the network node is the source node
of an IRAT handover. The example method includes initiating a
handover of a user equipment from a cell in the first RAN to a cell
in a second RAN, operating according to a second RAT, by sending a
handover-required indication towards the second RAN. The example
method includes, after handover of the user equipment to the cell
in the second RAN is completed, receiving a handover report from
the second RAN. The handover report comprises, for at least one
cell detected by the user equipment, a physical cell identifier for
the detected cell and a frequency identifier for the detected cell.
The network node then identifies a global cell identifier for the
at least one cell, based on the physical cell identifier and
frequency identifier, and adjusts one or more mobility settings
with respect to the at least one cell, in response to receiving the
handover report.
[0024] In some embodiments, the method further comprises sending,
towards the second RAN, information identifying one or more
frequencies to be measured by the user equipment, in a message
associated with the handover request. The information identifying
the one or more frequencies may comprise an EARFCN, in some
embodiments. In some embodiments, the network node still further
sends, in a message associated with the handover request,
measurement information indicating, for at least one of the one or
more frequencies, whether or not the user equipment should measure
CSG cells corresponding to the at least one of the one or more
frequencies. This measurement information may include a single
indicator indicating whether or not the user equipment should
measure CSG cells for all of the one or more frequencies, in some
embodiments. In others, the measurement information comprises a
separate indicator for each of the one or more frequencies.
[0025] In some embodiments, the network node sends information
identifying a measurement threshold in a message associated with
the handover request. In some embodiments, the received handover
report includes, for at least one cell detected by the user
equipment, a global cell identifier.
[0026] The techniques summarized above and detailed below allow a
drastic reduction of the configuration effort needed to store
details about potential LTE neighbor cells on GERAN BSSs and UTRAN
Radio Network Controllers (RNCs). The techniques also allow a
reduction of IRAT System Information Broadcast (SIB) reading
measurements for UEs in UTRAN, during the procedures of Unnecessary
IRAT Handover Detection.
[0027] The methods outlined herein allow a GERAN BSS or an UTRAN
RNC to discover new LTE neighboring cells that are reliable
handover candidates and to trigger configuration/retrieval of
information for such cells, so that procedures towards these cells
(e.g., handovers) can be started when needed. Some of the methods
detailed herein can also potentially limit the number of
measurements performed by a UE in GERAN.
[0028] In the detailed description that follows, the several
embodiments summarized above are described in detail, and
descriptions of corresponding apparatus for carrying out the
methods summarized above are described. It should be appreciated
however, that these embodiments are intended to be illustrative,
and not exhaustive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a diagram of combined LTE and GERAN/UTRAN
architectures.
[0030] FIG. 2 is a message sequence chart for the Unnecessary IRAT
Handover detection procedure, as per the current standards.
[0031] FIG. 3 illustrates the structure of an IRAT Measurement
Configuration IE.
[0032] FIG. 4 illustrates the structure of an IRAT Measurement
Configuration IE as used for handover from LTE to UTRAN.
[0033] FIG. 5 illustrates the structure of the HO Report IE message
as per TS 36.413.
[0034] FIG. 6 illustrates the structure of an IRAT Cell ID.
[0035] FIG. 7 illustrates the structure of an E-UTRAN CGI (ECGI)
IE.
[0036] FIG. 8 is a diagram of a management system.
[0037] FIG. 9 is a block diagram of a network node configured to
send HO Reports, according to some embodiments.
[0038] FIG. 10 illustrates the structure of an HO Report with a
Candidate PCI IE, according to some embodiments.
[0039] FIG. 11 illustrates a range bound for Candidate PCIs,
according to some embodiments.
[0040] FIG. 12 illustrates the structure of a Candidate PCI IE,
according to some embodiments.
[0041] FIG. 13 is a message sequence chart for enhancement of a HO
Report with PCI and frequency identifier of suitable LTE cells,
according to some embodiments.
[0042] FIG. 14 is a flowchart illustrating a method for sending HO
Reports, according to some embodiments.
[0043] FIG. 15 is a flowchart illustrating a method for adjusting
mobility settings in response to a HO Report, according to some
embodiments.
[0044] FIG. 16 is a block diagram of a functional implementation of
a network node for sending HO Reports, according to some
embodiments.
[0045] FIG. 17 is a block diagram of a functional implementation of
a network node for adjusting mobility settings in response to a HO
Report, according to some embodiments.
DETAILED DESCRIPTION
[0046] Inventive concepts will now be described more fully
hereinafter with reference to the accompanying drawings, in which
examples of embodiments of inventive concepts are shown. These
inventive concepts may, however, be embodied in many different
forms and should not be construed as limited to the embodiments set
forth herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and fully convey the
scope of present inventive concepts to those skilled in the art. It
should also be noted that these embodiments are not mutually
exclusive. Components from one embodiment may be tacitly assumed to
be present or used in another embodiment.
[0047] For purposes of illustration and explanation only,
embodiments of the present inventive concepts are described herein
in the context of operating in or in association with a RAN that
communicates over radio communication channels with mobile
terminals, also interchangeably referred to as wireless terminals
or UEs, using a particular RAT. More specifically, embodiments are
described in the context of the E-UTRAN, sometimes referred to as
the Evolved UMTS Terrestrial Radio Access Network and widely known
as the LTE system. However, it will be appreciated that the
techniques may be applied to other wireless networks, as well as to
successors of the E-UTRAN. Thus, references herein to signals using
terminology from the 3GPP standards for LTE should be understood to
apply more generally to signals having similar characteristics
and/or purposes, in other networks.
[0048] As used herein, the terms "mobile terminal," "wireless
terminal," "user equipment," or "UE" may be used to refer to any
device that receives data from and transmits data to a
communication network, any of which may be, for example, a mobile
telephone ("cellular" telephone), laptop/portable computer, pocket
computer, hand-held computer, desktop computer, a machine to
machine (M2M) or machine-type communication (MTC) device, a sensor
with a wireless communication interface, etc. Devices of any of
these types may be adapted, according to known techniques and
according to the additional techniques disclosed herein, for
operation in a device-to-device (D2D) mode, where such operation
may include the transmitting and receiving of certain signals that
are similar to or identical with corresponding signals used when
operating within a cellular network, i.e., in a
device-to-base-station operating mode.
[0049] In some embodiments, the term "network node" is used. This
term may refer to any type of radio network node or other node in
the fixed portion of a wireless communications network, which
communicates with a UE and/or with another network node. Examples
of network nodes are an eNodeB or eNB, a base station (BS),
multi-standard radio (MSR) radio node such as MSR BS, network
controller, radio network controller (RNC), base station controller
(BSC), relay, donor node controlling relay, base transceiver
station (BTS), access point (AP), transmission points, transmission
nodes, remote radio unit (RRU), remote radio head (RRH), nodes in
distributed antenna system (DAS), core network node (e.g., mobile
switching center or MSC, MME etc.), O&M, OSS, self-organizing
networks (SON), positioning node (e.g., Evolved Serving Mobile
Location Centre, or E-SMLC), minimization of drive-testing (MDT),
etc.
[0050] Several of the techniques and methods described herein are
implemented using electronic data processing circuitry and other
electronic hardware provided in a network node. In some cases, the
network node is a base station, and thus further includes radio
circuitry for communicating with one or more user equipments.
[0051] For example, FIG. 9 shows an example network node, in this
case a base station 10 (for example an LTE eNodeB or a GERAN BSS),
that can be used in some of the example embodiments described
herein. It will be appreciated that although a macro eNB will not,
in practice, be identical in size and structure to a small cell
eNB, for the purposes of illustration, the base stations 10 are
assumed to include similar components. Thus, whether or not base
station corresponds to a macro base station or a small cell base
station, it comprises a processing circuit that controls the
operation of the base station 10. The processing module 40, which
may include one or more microprocessors, microcontrollers, digital
signal processors, specialized digital logic, etc., is connected to
a transceiver module 42 with associated antenna(s) 44 that are used
to transmit signals to, and receive signals from, UEs in the
network. The base station 10 also comprises a memory circuit 46
that is connected to the processing module 40 and that stores
program and other information and data required for the operation
of the base station 10. Together, the processing module 40 and
memory circuit 46 may be referred to as a "processing circuit," and
are adapted, in various embodiments, to carry out one or more of
the network-based techniques described below.
[0052] Base station 10 also includes components and/or circuitry,
such as eNodeB interface 48, for allowing the base station 10 to
exchange information with other base stations 10 (for example, via
an X2 interface) and components and/or circuitry, such as core
network interface 49, for allowing the base station 10 to exchange
information with nodes in the core network (for example, via the S1
interface). It will be appreciated that base stations for use in
other types of networks (e.g., UTRAN or WCDMA RAN) will include
similar components to those shown in FIG. 9 and appropriate
interface circuitry 48, 49 for enabling communications with the
other network nodes in those types of networks (e.g., other base
stations, mobility management nodes and/or nodes in the core
network).
[0053] In a working group meeting, the RAN3 working group of 3GPP
agreed to a document, "Response LS on the routing information for
the unnecessary handover to another RAT detection," 3GPP doc.
R3-142602. The document states, "In order to avoid configuring in
the BSS for each and every involved ECGI the corresponding Global
eNB ID, RAN3 decided at RAN3 #85bis that the source Global eNB ID
should therefore also be conveyed in addition to the E-CGI and
TAI." The above statement may be interpreted to say that signaling
of the eNB ID (of the eNB requesting Unnecessary IRAT Handover
Detection) as part of the HO Required message from source eNB to
target GERAN BSS is sufficient to avoid configuring the BSS with
ECGI information. The same can be said of a UTRAN RNC target.
However, this assumed advantage of avoiding configuration efforts
in the target BSS or target RNC is only partially valid, because
knowledge of the eNB ID only avoids any need to configure the
target IRAT node (the target Inter-RAT node, i.e., the node
receiving handover of a UE from another RAT) of the source eNB's
Global eNB ID. Namely, the target IRAT node would not need any
configured parameters concerning the source eNB's cell, towards
which the HO Report IE should be addressed as part of the
Unnecessary IRAT Handover response. This is because the S1: HO
Required message triggering Unnecessary IRAT Handover Detection
would then already include the E-CGI, Tracking Area Identity (TAI),
and eNB ID of the cell from which the function was initiated and
where the HO Report should be routed.
[0054] However, the HO Report, constructed as shown in FIG. 5 and
as explained above, includes a candidate cell list, which contains
E-CGIs of cells detected by the UE while in the target RAT.
Therefore, the problem of configuring a target RAT node (e.g., a
GERAN BSS) with neighbor LTE cell information still applies,
because the node that has to send the HO Report IE to the source
eNB must be able to map the measurements provided by the UE
(fulfilling the measurement configuration criteria as provided in
the IRAT Measurement Configuration IE) to an E-CGI of the detected
cell. This has to be done for all the reported cells satisfying the
Unnecessary IRAT Handover detection criteria.
[0055] The problem can be better understood if it is considered
that a UE in GERAN reports only the PCI of the detected target LTE
cell, as well as an index identifying the LTE cell's frequency,
such index mapping to a list of frequencies broadcast by the
serving BSS to all UEs. Likewise, a UE in UTRAN would first report
the PCI and target frequency of the LTE cell detected. It may be
possible in UTRAN to trigger further measurements for the UE to
acquire more information about the detected cell, but such extra
measurements would incur long data traffic interruptions and
battery consumption. Therefore, it is desirable that the UE limits
LTE cell measurements to PCIs and frequencies.
[0056] For these reasons, if the E-CGI for all the LTE cells
reported by the UE and fulfilling the Unnecessary IRAT HO Detection
criteria must be included in the HO Report IE, then the target
GERAN BSS must be configured with mapping between all of the
reported PCIs and frequencies and ECGIs to be included in the HO
Report IE. Likewise, if it is desired to avoid extra inter-RAT
measurements, a target UTRAN RNC would need to be configured in a
similar way.
[0057] The techniques and apparatus described below enable the
possibility of reporting all LTE cells fulfilling the Unnecessary
IRAT HO Detection criteria in the HO Report IE without the need for
configuring the GERAN BSS or UTRAN RNC with global cell identifier
information for all neighbor cells. Further, these techniques allow
the acquisition of extra information for detected cells that
fulfill the Unnecessary IRAT Handover Detection criteria.
[0058] Another problem with the current standards arises from the
fact that, when requesting measurements from a UE being served in
GERAN, the BSS provides the E-UTRAN frequencies for macro neighbor
cells in one optional IE and the E-UTRAN frequencies for the Closed
Subscriber Group (CSG) neighbor cells in another optional IE in the
measurement request message. An example of such a message is the
PACKET MEASUREMENT ORDER message, sent on the Packet Associated
Control Channel (PACCH) from the GERAN BSS to the UE, containing
E-UTRAN frequencies for macro neighbor cells in the E-UTRAN
Parameters IE and E-UTRAN frequencies for CSG neighbor cells in the
E-UTRAN CSG Description IE (a condition for the BSS to send the
E-UTRAN CSG Description IE to the UE is that the UE has indicated
support for E-UTRAN CSG Cells Reporting in its capabilities). The
implication of excluding the E-UTRAN CSG Description IE from the
PACKET MEASUREMENT ORDER message is that the UE will not perform
any measurements on E-UTRAN CSG cells, thus the UE will not send
any measurement reports to the network for this type of cells.
[0059] As described above, the IRAT Measurement Configuration IE
contains a list of E-UTRAN frequencies indicated by the EARFCN IE
for which the target GERAN BSS will configure the UE to perform
measurements. However, the IRAT Measurement Configuration IE does
not contain any information that would help the GERAN BSS to
conclude whether it shall configure the UE to perform (and report)
measurements on E-UTRAN CSG neighbor cells for the indicated
E-UTRAN frequencies. This becomes more evident when cells are not
configured in the BSS for one or more of the indicated E-UTRAN
frequencies.
[0060] As a result of this, and depending on BSS implementation,
E-UTRAN CSG neighbor cells may potentially be excluded when
requesting measurements from the UE, hence only measurement results
from E-UTRAN macro neighbor cells may be included in the HO Report
IE although the intention when sending the Unnecessary IRAT
Handover Detection measurement request from the source eNB was to
also cover E-UTRAN CSG cells in the measurements.
[0061] It is worth noting that measurements of CSG cells are rather
costly for the UE while being served in GERAN, due to the size of
the routing information included in the measurement report, hence
it is most likely that some BSS (again depending on implementation)
will only request a UE to perform measurements on CSG cells when
configured to do so.
[0062] In a similar way, a BSS that requests a UE to perform
measurements on E-UTRAN macro neighbor cells as well as on E-UTRAN
CSG neighbor cells for all of the E-UTRAN frequencies included in
the IRAT Measurement Configuration IE, may cause an unnecessary
load to the UE for the reason indicated above.
[0063] A way to obviate the first of the problems described above
is to allow reporting of extra information in the HO Report IE. In
particular, such extra information should not require configuration
of information regarding neighbor LTE cells in the inter-RAT target
node.
[0064] One proposal to include a list of detected Physical Cell
Identities (PCIs) to the HO Report IE was already briefly described
in a way-forward document submitted at a 3GPP working group
meeting. See "Way Forward on GERAN LS on routing information for
unnecessary handover," 3GPP doc. R3-142539. However, this
enhancement would not be sufficient, because a PCI may be reused
across different frequencies. As a result, if only a list of
detected and suitable (for unnecessary IRAT Handover Detection
purposes) PCIs is provided in the HO Report IE, and in the event
that one or more of these PCIs are re-used across different
carriers, the receiving node would not know to which cells the PCIs
correspond, and would not be able to apply mobility parameters
changes to prevent the unnecessary IRAT handover in a reliable
way.
[0065] It is worth noting that such mobility parameter changes may
consist of prioritizing one of the reported LTE cells as a handover
target, in replacement of the inter-RAT handover target previously
selected. Therefore, applying such adjustments to the wrong cell
(wrongly identified due to reuse of the reported PCIs across
different carrier frequencies) may lead to major mobility problems
and to performance degradation.
[0066] A better solution, according to some embodiments, includes
for the case when the target inter-RAT node is not configured with
the mapping between PCI and frequency and the cell's ECGI, given
that a UE both in UTRAN and in GERAN reports a PCI and a frequency
indication for a detected LTE cell, then both the PCI and the
detected cell's frequency should be included in an opportune list
(or candidate list) in the HO Report IE, to assist the target eNB
in unequivocally identifying the cell that was detected and
reported by the UE. The following discussion thus includes details
on how to add PCI and frequency information for cells fulfilling
the Unnecessary IRAT Handover Detection criteria to the existing HO
Report IE.
[0067] To further specify the measurements expected from the
Unnecessary IRAT Handover Detection procedure, and by that
potentially limit the number of measurements performed by the UE
while served in GERAN, some extra information related to each
individual E-UTRAN frequency in the IRAT Measurement Configuration
IE could be supplied by the source eNB. This extra information
could, for, example consist of an indicator for each individual
E-UTRAN frequency, informing the BSS whether the UE (handed over
from LTE) shall be configured for measurements of (1) E-UTRAN macro
neighbor cells only, or (2) E-UTRAN CSG cells only, or (3) possibly
both cell types for the indicated E-UTRAN frequency. As an
alternative to a frequency-specific indicator, a common indicator
valid for all E-UTRAN frequencies included in the IRAT Measurement
Configuration IE could be supplied by the source eNB.
[0068] Thus, according to one aspect of the solutions detailed
herein, a node requested to configure and collect measurement for
the purpose of Unnecessary IRAT Handover Detection includes, in the
report of cells fulfilling the detection criteria, cells for which
cell configuration parameters such as the ECGI are not available.
Instead of the EGCIs for these cells, a list of PCIs and frequency
indicators for the detected cells is included in the Unnecessary
IRAT Handover Detection report, named HO Report IE.
[0069] In some embodiments of the presently disclosed techniques, a
list of PCIs and frequency identifiers such as the EUTRA Absolute
Radio Frequency Channel Number (EARFCN) is added to the current HO
Report IE sent over a RIM message as part of the SON Transfer
Request Container specified in 3GPP TS 36.413. Each PCI included in
such a list corresponds to a cell, detected and reported by the UE
configured with measurements for the Unnecessary Inter RAT Handover
Detection function, which has fulfilled the measurement conditions
specified in the measurement configuration sent to the target IRAT
node via handover signaling. As noted above, each PCI included in
the list by the target IRAT node may not have a corresponding ECGI
available at the target IRAT node. In some embodiments, the PCI and
frequency identifier are included only if the corresponding ECGI
has not been added in the existing Candidate Cell List IE of the HO
Report IE.
[0070] One possibility for the frequency identifier is the EARFCN,
which points at the center frequency of an LTE carrier. Such
parameter can be also replaced by an indication of a carrier
frequency band or frequency band on which the UE in the target IRAT
node was configured to perform measurements that brought to the
discovery of the corresponding PCI. For the sake of simplicity the
term "frequency identifier" will be used to specify any parameter
such as an EARFCN, or a carrier frequency or a cell frequency or
the frequency on which the UE in the target IRAT node was
configured to perform the measurements that lead to the detection
of the corresponding PCI.
[0071] According to this approach, the PCI and frequency identifier
are sent together in the HO Report IE if a detected cell fulfills
the Unnecessary IRAT Handover Detection criteria and if the target
IRAT node cannot deduce a corresponding ECGI. In some embodiments,
a way to amend the current specifications to achieve this is shown
in FIGS. 10 and 11, where a Candidate PCI List is added to the
structure of the HO Report IE. FIG. 12 shows an implementation of
the added Candidate PCI List added to the 3GPP standards, which
contains the PCI and the EARFCN of the detected cell.
[0072] As can be seen from the example in FIG. 10, the semantics
description of the Candidate PCI IE explains that the presence of
cells reported by means of PCI and EARFCN (or indeed any of the
Frequency Identifiers described above) excludes the presence of the
same cells in the existing Candidate Cell List IE. Indeed, if for
such cells the ECGI can be derived by the target RAT node, the cell
shall be reported by means of its ECGI in the Candidate Cell List
IE. The latter would avoid any confusion at the node receiving the
HO Report IE, such confusion for example consisting of receiving
the same cell twice, once in the Candidate Cell List IE and another
time in the Candidate PCI List IE. The latter might lead the
receiving node to understand that the cell reported by means of its
PCI is not configured (e.g., is not stored as a neighbor) in the
target IRAT node and as a consequence mechanisms may be triggered
to ensure that the cell is configured at the target IRAT node.
[0073] However, in an alternative approach, it would be possible
for the same cell to be identified in both the Candidate Cell List
IE and the Candidate PCI List IE, provided that the receiving node
understands that the cell reported in both lists is configured at
the target IRAT node.
[0074] To control the amount and type of information provided in
the HO Report IE as per previous embodiments, some embodiments of
the techniques described above provide for an indication to be
provided from the source eNB to the target IRAT node, the
indication indicating whether or not cells transmitting a CSG ID
should be included in the Unnecessary IRAT Handover Detection and
reporting mechanism. In various embodiments or instances, they
could be included together with other cells or included alone, i.e.
only cells transmitting a CSG ID--closed, hybrid, or both--could be
included, or excluded. Such indication may comprise information on
whether to include CSG cells, namely cells that can only be
accessible by UEs that are member of the CSG ID; hybrid cells,
i.e., cells provided with a CSG ID and accessible to all UEs but
where UEs that are member of the CSG ID may be treated in a
prioritized way, or both closed and hybrid cells. The indication
may indicate whether to include closed cells and/or hybrid cells
alone or whether to include closed cells and/or hybrid cells with
other cells. The indication could be provided as part of the IRAT
Measurement Configuration IE as discussed above, namely for both
the cases of target GERAN RAT and target UTRAN RAT. The indication
may be provided on a per EARFCN indicated by source eNB for
Unnecessary IRAT Handover Detection, or as a general indication for
all the EARFCNs indicated in the IRAT Measurement Configuration IE.
With such indication, the target RAT node may understand whether to
collect measurements and run the unnecessary IRAT Handover
detection for CSG-type cells (i.e. closed or hybrid cells) in
addition to (or instead of) non-CSG-type cells.
[0075] FIG. 13 illustrates an example message flow for the
Unnecessary IRAT Handover Detection procedure as modified by the
techniques described herein. In this non-limiting example, the base
station of the first RAN 204 is an LTE eNodeB, and decides to
handover a UE to another cell. The target cell is served by the
base station of the target RAN 202, which is a GERAN BSS. In step
1, the eNodeB of the first RAN 204 indicates to the core network
that a handover is required for a UE in the cell of the first RAN
204. The HANDOVER REQUIRED message may include an IRAT Measurement
Configuration IE, as shown in FIG. 4. In step 2, the core network
sends a HANDOVER REQUEST message to the GERAN BSS of the target RAN
202. Steps 3 and 4 show a HANDOVER REQUEST ACK and a HANDOVER
COMMAND.
[0076] At this point, the GERAN BSS configures the UE with
Unnecessary IRAT Handover measurements. Detected cells with
measurements that exceed measurement thresholds are identified. If
the GERAN BSS determines that an ECGI is available for a cell, it
is included in the Candidate Cell List IE of a HO Report IE to be
sent to the eNodeB. If the GERAN BSS determines that an ECGI is not
available, a PCI and Frequency Identifier are included in the
Candidate PCI List IE of the HO Report IE. The Frequency Identifier
can be a EARFCN.
[0077] At step 5, a RIM Request transfer is sent to the eNodeB and
may include the HO Report IE. The eNodeB identifies cells by the
ECGI in the Candidate Cell List IE. The eNodeB also identifies
cells that do not have ECGIs in the Candidate Cell List IE by the
PCI and EARFCN in the Candidate PCI List IE. In some cases, this
may include determining the ECGI for such a cell from the PCI and
EARFCN. The eNodeB then adjusts mobility settings towards the
target cell of the target RAN 202 or to detected cells reported in
the HO Report IE, which has been enhanced in this embodiment by the
Candidate PCI List IE.
[0078] Given the above detailed examples of techniques for
improving the Unnecessary IRAT Handover detection process, it
should be appreciated that these techniques may be applied more
generally. FIG. 14 illustrates an example method 1400 that may be
carried out by a network node operating in a first RAN 202
according to a first RAT. In this case, the network node is a base
station, such as base station 10, for the cell targeted in an IRAT
handover.
[0079] As shown at blocks 1410 and 1440, the method 1400 includes
receiving a handover request for a user equipment from a cell in
the second RAN 204 operating according to a second RAT and, after
handover of the user equipment to a cell in the first RAN 202 is
completed, configuring the user equipment to measure one or more
frequencies corresponding to the second RAN 204. The method 1400
includes, based on measurements reported by the user equipment for
the one or more frequencies for which the user equipment was
configured to measure, identifying one or more detected cells
exceeding a measurement threshold, as shown at block 1450, and
sending a handover report towards the second RAN 204, as shown at
block 1460. The handover report comprises, for at least one
detected cell exceeding the measurement threshold, a physical cell
identifier for the detected cell and a frequency identifier for the
detected cell.
[0080] In some embodiments, the network node receives information
identifying the one or more frequencies corresponding to the second
RAN 204 in a message associated with the handover request. This is
shown at block 1420. In some of these embodiments, the information
identifying the one or more frequencies comprises an EARFCN. In
further embodiments, the network node also receives, in a message
associated with the handover request, measurement information
indicating, for at least one of the one or more frequencies,
whether or not the user equipment should measure CSG cells
corresponding to the at least one of the one or more frequencies.
This is shown at block 1430. In these embodiments, configuring the
user equipment to measure one or more frequencies corresponding to
the second RAN 204 comprises configuring the user equipment to
measure CSG cells or not to measure CSG cells, according to the
received measurement information. The measurement indicator in some
of these embodiments may be a single indicator indicating whether
or not the user equipment should measure CSG cells for all of the
one or more frequencies. In others of these embodiments, a separate
indicator is provided for each of the one or more frequencies.
[0081] In some embodiments, the handover report includes, for at
least one of the detected cells exceeding the measurement
threshold, a global cell identifier. In some embodiments, a
physical cell identifier and frequency identifier is included only
for those detected cells for which a global cell identifier is not
known or could not be derived from the measurements reported by the
user equipment.
[0082] FIG. 15 illustrates another example method 1500 according to
the present techniques, again carried out in a network node, such
as base station 10, operating in a first RAN 204 according to a
first RAT. In this case, however, the network node is the source
node of an IRAT handover, rather than the target node as in FIG.
14. Thus, the "first" RAN and "first" RAT in this case may differ
from the first RAN and first RAT discussed in connection with FIG.
14. For example, the first RAN in FIG. 14 was RAN 202. In FIG. 15,
the first RAN is RAN 204.
[0083] As shown at block 1510, the example method 1500 includes
initiating a handover of a user equipment from a cell in the first
RAN 204 to a cell in the second RAN 202. This may be done by
sending a handover-required indication towards the second RAN 202.
After handover of the user equipment to the cell in the second RAN
202 is completed, the network node receives a handover report from
the second RAN 202, as shown at block 1520. The handover report
comprises, for at least one cell detected by the user equipment, a
physical cell identifier for the detected cell and a frequency
identifier for the detected cell. As shown at block 1530, the
network node then identifies a global cell identifier for the at
least one cell, based on the physical cell identifier and frequency
identifier. Finally, as shown at block 1540, the network node
adjusts one or more mobility settings with respect to the cell in
the second RAN 202 and/or with respect to the at least one cell
detected by the user equipment, in response to receiving the
handover report.
[0084] In some embodiments, the method further comprises sending,
towards the second RAN 202, information identifying one or more
frequencies to be measured by the user equipment, in a message
associated with the handover-required indication. (This may be same
message as the handover request, in some embodiments). The
information identifying the one or more frequencies may comprise an
EARFCN. In some embodiments, the network node still further sends,
in a message associated with the handover-required indication,
measurement information indicating, for at least one of the one or
more frequencies, whether or not the user equipment should measure
CSG cells corresponding to the at least one of the one or more
frequencies. This measurement information may include a single
indicator indicating whether or not the user equipment should
measure CSG cells for all of the one or more frequencies, in some
embodiments. In others, the measurement information comprises a
separate indicator for each of the one or more frequencies.
[0085] In some embodiments, the network node sends information
identifying a measurement threshold in a message associated with
the handover-required indication. In some embodiments, the received
handover report includes, for at least one cell detected by the
user equipment, a global cell identifier.
[0086] Embodiments of the presently disclosed techniques include
the several methods described above, including the methods 1400 and
1500 illustrated in the process flow diagrams of FIGS. 14 and 15,
as well as variants thereof. Other embodiments include network node
apparatuses configured to carry out one or more of these methods.
In some embodiments of the invention, processing circuits, such as
the processing module 40 and memory circuit 46 of FIG. 9, are
configured to carry out one or more of the techniques described in
detail above. Likewise, other embodiments may include network nodes
that include one or more such processing circuits. In some cases,
these processing circuits are configured with appropriate program
code, stored in one or more suitable memory devices, to implement
one or more of the techniques described herein. Of course, it will
be appreciated that not all of the steps of these techniques are
necessarily performed in a single microprocessor or even in a
single module.
[0087] It will further be appreciated that various aspects of the
above-described embodiments can be understood as being carried out
by functional "modules" corresponding to the method steps
illustrated in FIGS. 14 and 15. These functional modules may be
program instructions executing on an appropriate processor circuit,
hard-coded digital circuitry and/or analog circuitry, or
appropriate combinations thereof, e.g., in network nodes having
hardware configurations like that shown in FIG. 9.
[0088] For example, FIG. 16 illustrates an example functional
module or circuit architecture as may be implemented in base
station 10, e.g., based on the processing module 40 and memory
circuit 46, of a first RAN operating according to a first RAT. The
illustrated embodiment at least functionally includes a receiving
module 1602 for receiving a handover request for a user equipment
from a cell in a second RAN operating according to a second RAT.
The implementation also includes a configuration module 1604 for,
after handover of the user equipment to a cell in the first RAN is
completed, configuring the user equipment to measure one or more
frequencies corresponding to the second RAN. The implementation
includes an identifying module 1606 for, based on measurements
reported by the user equipment for the one or more frequencies,
identifying one or more detected cells exceeding a measurement
threshold. The implementation further includes a sending module
1608 for sending a handover report towards the second RAN. The
handover report includes, for at least one detected cell exceeding
the measurement threshold, a physical cell identifier for the
detected cell and a frequency identifier for the detected cell.
[0089] In another example, FIG. 17 illustrates an example
functional module or circuit architecture as may be implemented in
base station 10, e.g., based on the processing module 40 and memory
circuit 46, of a first RAN operating according to a first RAT. The
illustrated embodiment at least functionally includes a handover
module 1702 for initiating a handover of a user equipment from a
cell in the first RAN to a cell in a second RAN, operating
according to a second RAT, by sending a handover-required
indication towards the second RAN. The implementation also includes
a receiver module 1704 for, after handover of the user equipment to
the cell in the second RAN is completed, receiving a handover
report from the second RAN. The handover report comprises, for at
least one cell detected by the user equipment, a physical cell
identifier for the detected cell and a frequency identifier for the
detected cell. The implementation includes an identification module
1706 for identifying a global cell identifier for the at least one
cell, based on the physical cell identifier and frequency
identifier. The implementation further includes a mobility module
1708 for adjusting one or more mobility settings with respect to
the cell and/or with respect to the at least one cell, in response
to receiving the handover report.
[0090] It will be appreciated by the person of skill in the art
that various modifications may be made to the above described
embodiments without departing from the scope of the present
invention. For example, although embodiments of the present
invention have been described with examples that reference a
communication system compliant to the 3GPP-specified LTE standards,
it should be noted that the solutions presented may be equally well
applicable to other networks. The specific embodiments described
above should therefore be considered exemplary rather than limiting
the scope of the invention. Because it is not possible, of course,
to describe every conceivable combination of components or
techniques, those skilled in the art will appreciate that the
present invention can be implemented in other ways than those
specifically set forth herein, without departing from essential
characteristics of the invention. The present embodiments are thus
to be considered in all respects as illustrative and not
restrictive.
[0091] In the present description of various embodiments of present
inventive concepts, it is to be understood that the terminology
used herein is for the purpose of describing particular embodiments
only and is not intended to be limiting of present inventive
concepts. Unless otherwise defined, all terms (including technical
and scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which present
inventive concepts belongs. It will be further understood that
terms, such as those defined in commonly used dictionaries, should
be interpreted as having a meaning that is consistent with their
meaning in the context of this specification and the relevant art
and will not be interpreted in an idealized or overly formal sense
expressly so defined herein.
[0092] When an element is referred to as being "connected",
"coupled", "responsive", or variants thereof to another element, it
can be directly connected, coupled, or responsive to the other
element or intervening elements may be present. In contrast, when
an element is referred to as being "directly connected", "directly
coupled", "directly responsive", or variants thereof to another
element, there are no intervening elements present. Like numbers
refer to like elements throughout. Furthermore, "coupled",
"connected", "responsive", or variants thereof as used herein may
include wirelessly coupled, connected, or responsive. As used
herein, the singular forms "a", "an" and "the" are intended to
include the plural forms as well, unless the context clearly
indicates otherwise. Well-known functions or constructions may not
be described in detail for brevity and/or clarity. The term
"and/or" includes any and all combinations of one or more of the
associated listed items.
[0093] It will be understood that although the terms first, second,
third, etc. may be used herein to describe various
elements/operations, these elements/operations should not be
limited by these terms. These terms are only used to distinguish
one element/operation from another element/operation. Thus a first
element/operation in some embodiments could be termed a second
element/operation in other embodiments without departing from the
teachings of present inventive concepts. The same reference
numerals or the same reference designators denote the same or
similar elements throughout the specification.
[0094] As used herein, the terms "comprise", "comprising",
"comprises", "include", "including", "includes", "have", "has",
"having", or variants thereof are open-ended, and include one or
more stated features, integers, elements, steps, components or
functions but does not preclude the presence or addition of one or
more other features, integers, elements, steps, components,
functions or groups thereof. Furthermore, as used herein, the
common abbreviation "e.g.", which derives from the Latin phrase
"exempli gratia," may be used to introduce or specify a general
example or examples of a previously mentioned item, and is not
intended to be limiting of such item. The common abbreviation
"i.e.", which derives from the Latin phrase "id est," may be used
to specify a particular item from a more general recitation.
[0095] Example embodiments have been described herein, with
reference to block diagrams and/or flowchart illustrations of
computer-implemented methods, apparatus (systems and/or devices)
and/or computer program products. It is understood that a block of
the block diagrams and/or flowchart illustrations, and combinations
of blocks in the block diagrams and/or flowchart illustrations, can
be implemented by computer program instructions that are performed
by one or more computer circuits. These computer program
instructions may be provided to a processor circuit of a general
purpose computer circuit, special purpose computer circuit, and/or
other programmable data processing circuit to produce a machine,
such that the instructions, which execute via the processor of the
computer and/or other programmable data processing apparatus,
transform and control transistors, values stored in memory
locations, and other hardware components within such circuitry to
implement the functions/acts specified in the block diagrams and/or
flowchart block or blocks, and thereby create means (functionality)
and/or structure for implementing the functions/acts specified in
the block diagrams and/or flowchart block(s).
[0096] These computer program instructions may also be stored in a
tangible computer-readable medium that can direct a computer or
other programmable data processing apparatus to function in a
particular manner, such that the instructions stored in the
computer-readable medium produce an article of manufacture
including instructions which implement the functions/acts specified
in the block diagrams and/or flowchart block or blocks.
Accordingly, embodiments of present inventive concepts may be
embodied in hardware and/or in software (including firmware,
resident software, micro-code, etc.) running on a processor such as
a digital signal processor, which may collectively be referred to
as "circuitry," "a module" or variants thereof.
[0097] It should also be noted that in some alternate
implementations, the functions/acts noted in the blocks may occur
out of the order noted in the flowcharts. For example, two blocks
shown in succession may in fact be executed substantially
concurrently or the blocks may sometimes be executed in the reverse
order, depending upon the functionality/acts involved. Moreover,
the functionality of a given block of the flowcharts and/or block
diagrams may be separated into multiple blocks and/or the
functionality of two or more blocks of the flowcharts and/or block
diagrams may be at least partially integrated. Finally, other
blocks may be added/inserted between the blocks that are
illustrated, and/or blocks/operations may be omitted without
departing from the scope of inventive concepts. Moreover, although
some of the diagrams include arrows on communication paths to show
a primary direction of communication, it is to be understood that
communication may occur in the opposite direction to the depicted
arrows.
[0098] Many variations and modifications can be made to the
embodiments without substantially departing from the principles of
the present inventive concepts. All such variations and
modifications are intended to be included herein within the scope
of present inventive concepts. Accordingly, the above disclosed
subject matter is to be considered illustrative, and not
restrictive, and the appended examples of embodiments are intended
to cover all such modifications, enhancements, and other
embodiments, which fall within the spirit and scope of present
inventive concepts. Thus, to the maximum extent allowed by law, the
scope of present inventive concepts are to be determined by the
broadest permissible interpretation of the present disclosure, and
shall not be restricted or limited by the foregoing detailed
description.
* * * * *
References