WO2013044512A1 - Mobile robustness optimization in carrier aggregation - Google Patents

Mobile robustness optimization in carrier aggregation Download PDF

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Publication number
WO2013044512A1
WO2013044512A1 PCT/CN2011/080477 CN2011080477W WO2013044512A1 WO 2013044512 A1 WO2013044512 A1 WO 2013044512A1 CN 2011080477 W CN2011080477 W CN 2011080477W WO 2013044512 A1 WO2013044512 A1 WO 2013044512A1
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WO
WIPO (PCT)
Prior art keywords
handover
base station
measurement results
organizing network
secondary cell
Prior art date
Application number
PCT/CN2011/080477
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French (fr)
Inventor
Yizhi Yao
Original Assignee
Nokia Siemens Networks Oy
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Publication date
Application filed by Nokia Siemens Networks Oy filed Critical Nokia Siemens Networks Oy
Priority to PCT/CN2011/080477 priority Critical patent/WO2013044512A1/en
Publication of WO2013044512A1 publication Critical patent/WO2013044512A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H04W36/0085—Hand-off measurements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0069—Transmission or use of information for re-establishing the radio link in case of dual connectivity, e.g. decoupled uplink/downlink
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0069—Transmission or use of information for re-establishing the radio link in case of dual connectivity, e.g. decoupled uplink/downlink
    • H04W36/00692—Transmission or use of information for re-establishing the radio link in case of dual connectivity, e.g. decoupled uplink/downlink using simultaneous multiple data streams, e.g. cooperative multipoint [CoMP], carrier aggregation [CA] or multiple input multiple output [MIMO]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H04W36/00835—Determination of neighbour cell lists
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H04W36/00837—Determination of triggering parameters for hand-off
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/02—Arrangements for optimising operational condition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/08—Testing, supervising or monitoring using real traffic

Definitions

  • the present invention relates to mobile robustness optimization (MRO) in carrier aggregation (CA) in self-organizing networks (SON).
  • MRO mobile robustness optimization
  • CA carrier aggregation
  • SON self-organizing networks
  • CA Carrier aggregation
  • SON MRO Self-organizing networks mobile robustness optimization
  • LTE long term evolution
  • CA SON MRO enhancement for CA
  • Standardization is needed to enable multi-vendor deployment and interworking .
  • the SON MRO intra-LTE mainly addresses the handover failure cases, like e.g . the handover is too early, too late or to the wrong cell. This works for the case of a one-to-one cell handover without CA.
  • the handover will be at the multiple-to-multiple cells granularity (including one Pcell (primary cell) and several Scells (secondary cells) for both the source and target side).
  • the Scell may be dropped before or after handover, and the Scell may be changed after the handover and such a Scell drop or change will also surely impact the UE experience and this is also an important factor to evaluate the handover performance.
  • the current MRO function does not cover yet the cases of Scell drop and change, because as long as the Pcell is successfully switched, there will be no handover failure report.
  • a self- organizing network comprising:
  • the measurement results include at least one of the following :
  • the secondary cell drops before handover are measured for each base station, carrier aggregation group and/or for each cell;
  • the secondary cell drops before handover are measured based on received user equipment measurement reports from the primary cell within a configurable timer
  • the secondary cell change after handover, and/or the primary cell change after handover are measured for each base station, each carrier aggregation group, each cell, and/or for each neighbour relation;
  • the secondary cell drops after handover are measured based on received user equipment measurement reports from a new primary cell within a configurable timer after receiving a successful incoming handover;
  • the secondary cell drops before handover and the secondary cell drops after handover are measured based on the data transmission success rate with the Scell within a configurable timer after receiving a successful incoming handover;
  • RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the same or different RRCConnectionReconfiguration messages, some SCells are added and some SCells are released, after receiving a successful incoming handover;
  • RRCConnectionReconfiguration messages sent to the user equipment within a configurable timer, while in the RRCConnectionReconfiguration message the primary cell is changed, after receiving a successful incoming handover;
  • the measurement secondary cell drops before handover are measured at a source base station, and reported to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
  • the measurement results are measured at a source base station, and reported to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
  • the measurement results are measured at a target base station and reported to a source base station in case of a distributed self organizing network architecture with an X2 interface;
  • the measurement results are measured at a target base station and reported to an element manager in case of a distributed self organizing network architecture without an X2 interface, and the element manager forwards the measurement results to the source base station;
  • the measurement results are measured at a target base station and reported to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
  • the measurement results are forwarded to a network manager in case of a centralized self organizing network architecture and the self organizing network server is at network manager level;
  • the measurement results are forwarded to a network manager in case of the source base station and the target base station are managed by different element managers;
  • a base station in a self-organizing network comprising:
  • a measuring unit configured to measure measurement results related to the primary cell and the secondary cells
  • the measurement results include at least one of the following :
  • the secondary cell drops before handover are measured for each base station, carrier aggregation group and/or for each cell;
  • the secondary cell drops before handover are measured based on received user equipment measurement reports from the primary cell within a configurable timer
  • the secondary cell change after handover, and/or the primary cell change after handover are measured for each base station, each carrier aggregation group, each cell, and/or for each neighbour relation;
  • the secondary cell drops after handover are measured based on received user equipment measurement reports from a new primary cell within a configurable timer after receiving a successful incoming handover; - the secondary cell drops before handover and the secondary cell drops after handover are measured based on the data transmission success rate with the Scell within a configurable timer after receiving a successful incoming handover;
  • RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the same or different RRCConnectionReconfiguration messages, some SCells are added and some SCells are released, after receiving a successful incoming handover;
  • RRCConnectionReconfiguration messages sent to the user equipment within a configurable timer, while in the RRCConnectionReconfiguration message the primary cell is changed, after receiving a successful incoming handover; - the base station is s source base station configured to measure the measurement secondary cell drops before handover, and to report the measurement to an element manager in case of a centralized self
  • the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
  • the base station is a source base station configured to measure the measurement results, and to report the measurement to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
  • the base station is a target base station configured to measure the measurement results and to report the measurement results to a source base station in case of a distributed self organizing network architecture with an X2 interface;
  • the base station is a target base station configured to measure the measurement results and to report the measurement results to an element manager in case of a distributed self organizing network architecture without an X2 interface, and the element manager forwards the
  • the base station is a target base station configured to measure the measurement results and to report the measurement results to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
  • the measurement results are forwarded to a network manager in case of a centralized self organizing network architecture and the self organizing network server is at network manager level;
  • the measurement results are forwarded to a network manager in case of the source base station and the target base station are managed by different element managers;
  • the reported measurement results are used for evaluating the handover performance, evaluating the mobile robustness optimization performance and correcting handover parameters.
  • a computer program product comprising code means adapted to produce steps of any of the methods as described above when loaded into the memory of a computer.
  • a computer program product as defined above, wherein the computer program product comprises a computer-readable medium on which the software code portions are stored .
  • Fig . 1 is a block diagram illustrating a SON architecture to which
  • Fig . 2 is a block diagram illustrating another SON architecture to which embodiments of the present invention are applicable;
  • Fig . 3 is a block diagram showing a base station according to an embodiment of the present invention.
  • Fig . 4 is a flowchart illustrating processing of the base station 10.
  • Figs. 1 and 2 illustrate examples of SON architectures to which
  • Fig . 1 shows a distributed architecture with an X2/lur interface that connects two eNBs (enhanced NodeB) or RNCs (radio network controller) with each other, and which are further connected to an element manager EM.
  • the eNB can be managed by the same or different element managers.
  • Fig . 2 further shows an architecture which is distributed without an X2/lur interface and an centralized architecture.
  • the SON functions are located at the eNB, and in the centralized SON, the SON functions are located at element manager, network manager (NM) or SON server.
  • NM network manager
  • the eNB performs measurements about the Scell drops before or after the handover, and performs measurements about Scell changes after the handover as well as measurements about the Pcell change after the handover.
  • the eNB measures the Scell drops before the handover for each eNB, each CA group (i.e. a group of cells that can be aggregated together) and/or for each cell.
  • the information about Scell drops before HO is helpful for the source eNB to judge if the handover is too-late (for Scells).
  • the eNB measures the Scell drops after the handover for each eNB, each CA group, each cell, and/or for each neighbour relation.
  • the Scell drops after handover can be measured firstly at a target eNB, and the target eNB then reports the measurement results back to the source eNB (for distributed MRO architectures with X2 interface, as illustrated in Fig . 1), or report them back to the element manager (EM) (for centralized MRO architecture and distributed without X2, as illustrated in Fig. 2).
  • EM element manager
  • the (target) eNB After receiving a successful incoming handover, the (target) eNB can measure the Scell drops:
  • Scell has a poor signal (below a certain value or margin in average); or b) if data transmission success rate with this Scell is below a certain value within the configurable timer, or
  • the (target) eNB released the Scell to the UE due to air interface quality reasons within the configurable timer.
  • the information about Scell drops after the handover is helpful for the source eNB to judge if the handover is too early or to wrong cells (for Scells).
  • the eNB measures the Scell changes after the handover for each eNB, each CA group, each cell, and/or for each neighbour relation.
  • the Scell changes after handover can be measured firstly at target eNB, and the target eNB then reports the measurement results back to the source eNB (for distributed MRO architecture with X2, as illustrated in Fig. 1), or reports them back to the OAM (operations, administration and maintenance) (for centralized MRO architecture and distributed without X2, as illustrated in Fig. 2).
  • the (target) eNB After receiving a successful incoming handover, the (target) eNB can measure the Scell changes from the RRCConnectionReconfiguration messages sent to the UE due to air interface quality reason within the configurable timer, while in the same or different
  • the information about Scell changes after the handover is helpful for the source eNB to judge if the handover is to wrong cells (for Scells, and which should be better candidate Scells for handover). 4) As to the Pcell change after the handover, the eNB measures the Pcell change after the handover for each eNB, each CA group, each cell, and/or for each neighbour relation.
  • the Pcell change after handover can be measured firstly at target eNB, and the target eNB then reports the measurement results back to the source eNB (for distributed MRO architecture with X2, as illustrated in Fig. 1), or reports them back to OAM (for centralized MRO architecture and distributed without X2, as illustrated in Fig . 2).
  • the (target) eNB can measure the Pcell change from the RRCConnectionReconfiguration message sent to the UE within the configurable timer, while in the
  • the Pcell is changed .
  • the information about Pcell changes after the handover is helpful for the source eNB to judge if the handover is to an improper Pcell (and which should be better candidate Pcell for handover).
  • the source eNB will take the reported Scell drops/changes and/or Pcell change to be part of input to correct the handover parameters.
  • the EM will forward the reported Scell drops/changes and/or Pcell change to the source eNB, which requires Itf-N support if the source eNB is not managed by the same EM . Then, the source eNB will take the reported Scell drops/changes and/or Pcell change to be part of input to correct the handover parameters.
  • the EM will forward the reported Scell drops/changes and/or Pcell change to the SON server if separated, which requires Itf-N support if the SON server is at NM level.
  • the SON server will then take the reported Scell drops/changes and/or Pcell change to be part of input to correct the handover parameters.
  • the timers/thresholds used for detecting the above described events may be configurable. Certain embodiments of the present invention are implemented in the eNB, EM, NM or a separate SON server.
  • 3GPP 32. series, 36. series and 25. series stage 2 description show in the typical format of a 3GPP 32. series, 36. series and 25. series stage 2 description, how the solution according to certain embodiments of the invention can be realized .
  • 3GPP TS 36.300 the following is added .
  • the following information is added into the "Handover Report" message, which is sent by the eNB to report a handover failure event, or into a new message (like, for example, CA Handover Report) for the case of a distributed architecture with X2 only.
  • REQ_FUN_x "Mobility Robustness Optimization also aims at detecting and enabling correction of the following problems in a CA scenario :
  • IOC information object class
  • 3GPP TS 32.522 the following targets and performance measurements are added to 3GPP TS 32.522 :
  • Fig . 3 is a block diagram showing a base station according to an embodiment of the present invention.
  • the base station 10 comprises a measuring unit 11 and a transceiver 12 connected to the measuring unit.
  • Fig . 4 is a flowchart illustrating processing of the base station 10.
  • the base station 10 measures measurement results related to the primary cell and the secondary cells.
  • the base station 10 forwards the measurement results to an element manager, base station or server.
  • an element manager base station or server.
  • the base station may comprise further units that are necessary for its respective operation. However, a description of these units is omitted in this specification.
  • the arrangement of the functional blocks of the devices is not construed to limit the invention, and the functions may be performed by one block or further split into sub- blocks.
  • any method step is suitable to be implemented as software or by hardware without changing the idea of the embodiments and its modification in terms of the functionality implemented;
  • CMOS Complementary MOS
  • BiMOS Bipolar MOS
  • BiCMOS Bipolar CMOS
  • ECL emitter Coupled Logic
  • TTL Transistor- Transistor Logic
  • - devices, units or means e.g . the above-defined apparatuses and user equipments, or any one of their respective units/means
  • devices, units or means can be implemented as individual devices, units or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device, unit or means is preserved;
  • an apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor;
  • a device may be regarded as an apparatus or as an assembly of more than one apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example.
  • respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts.
  • the mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.
  • any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention.
  • Devices and means can be implemented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved . Such and similar principles are to be considered as known to a skilled person.
  • Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.
  • a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The present invention provides a method, apparatus and a computer program product for mobile robustness optimization in carrier aggregation. The present invention includes, in performing multiple-to-multiple-cell handover with carrier aggregation in a in a self-organizing network including at least one primary cell and one or more secondary cells, measuring, at a base station, measurement results related to the primary cell and the secondary cells, wherein the measurement results include at least secondary cell drops before handover, secondary cell drops after handover, secondary cell changes after handover, and primary cell change after handover.

Description

MOBILE ROBUSTNESS OPTIMIZATION IN CARRIER AGGREGATION
Field of the invention
The present invention relates to mobile robustness optimization (MRO) in carrier aggregation (CA) in self-organizing networks (SON).
Background of the invention
Carrier aggregation (CA) is a radio technology which allows combining several carriers of different cells such that a user equipment (UE), and finally the end user, has a higher bandwidth available, which allows a better user experience.
Self-organizing networks mobile robustness optimization (SON MRO) automatically optimizes the handover related parameters to improve the handover performance and reduce the handover failures. Recently, SON MRO for long term evolution (LTE) has been standardized, whereas SON MRO enhancement for CA has not been standardized yet. Standardization, however, is needed to enable multi-vendor deployment and interworking . The SON MRO intra-LTE mainly addresses the handover failure cases, like e.g . the handover is too early, too late or to the wrong cell. This works for the case of a one-to-one cell handover without CA.
However, in CA, the handover will be at the multiple-to-multiple cells granularity (including one Pcell (primary cell) and several Scells (secondary cells) for both the source and target side). Thus, even though in the success handover cases (i.e. when the Pcell is not dropped), the Scell may be dropped before or after handover, and the Scell may be changed after the handover and such a Scell drop or change will also surely impact the UE experience and this is also an important factor to evaluate the handover performance. The current MRO function does not cover yet the cases of Scell drop and change, because as long as the Pcell is successfully switched, there will be no handover failure report.
Another aspect is about the Pcell change after the handover. If there occurs a quick Pcell change after handover, this means that the source eNB selected improper cells as Pcell to handover. Also this change impacts the user experience and handover performance though there is no handover failure. Summary of the Invention
According to the present invention, there are provided methods, apparatuses and a computer program product for mobile robustness optimization in carrier aggregation.
According to an aspect of the invention there is provided a method in a self- organizing network, comprising :
in performing multiple-to-multiple-cell handover with carrier aggregation in a network including at least one primary cell and one or more secondary cells,
measuring, at a base station, measurement results related to the primary cell and the secondary cells,
wherein the measurement results include at least one of the following :
- secondary cell drops before handover,
- secondary cell drops after handover,
- secondary cell changes after handover, and
- primary cell change after handover. According to further refinements of the invention as defined under the above aspects
- the secondary cell drops before handover are measured for each base station, carrier aggregation group and/or for each cell;
- the secondary cell drops before handover are measured based on received user equipment measurement reports from the primary cell within a configurable timer;
- the secondary cell drops after handover, the secondary cell change after handover, and/or the primary cell change after handover are measured for each base station, each carrier aggregation group, each cell, and/or for each neighbour relation;
- the secondary cell drops after handover are measured based on received user equipment measurement reports from a new primary cell within a configurable timer after receiving a successful incoming handover;
- the secondary cell drops before handover and the secondary cell drops after handover are measured based on the data transmission success rate with the Scell within a configurable timer after receiving a successful incoming handover;
- the secondary cell drops after handover are measured from
RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the RRCConnectionReconfiguration message, the sCellToReleaseList is not empty, after receiving a successful incoming handover;
- the secondary cell changes after handover are measured from
RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the same or different RRCConnectionReconfiguration messages, some SCells are added and some SCells are released, after receiving a successful incoming handover;
- the primary cell change after handover is measured from
RRCConnectionReconfiguration messages sent to the user equipment within a configurable timer, while in the RRCConnectionReconfiguration message the primary cell is changed, after receiving a successful incoming handover;
- the measurement secondary cell drops before handover are measured at a source base station, and reported to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
- the measurement results are measured at a source base station, and reported to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
- the measurement results are measured at a target base station and reported to a source base station in case of a distributed self organizing network architecture with an X2 interface;
- the measurement results are measured at a target base station and reported to an element manager in case of a distributed self organizing network architecture without an X2 interface, and the element manager forwards the measurement results to the source base station;
- the measurement results are measured at a target base station and reported to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
- the measurement results are forwarded to a network manager in case of a centralized self organizing network architecture and the self organizing network server is at network manager level;
- the measurement results are forwarded to a network manager in case of the source base station and the target base station are managed by different element managers;
4 EIE1 10213PCT - the reported measurement results are used for evaluating the handover performance, evaluating the mobile robustness optimization performance and correcting handover parameters. According to another aspect of the present invention, there is provided a base station in a self-organizing network, comprising :
in performing multiple-to-multiple-cell handover with carrier aggregation in a network including at least one primary cell and one or more secondary cells,
a measuring unit configured to measure measurement results related to the primary cell and the secondary cells,
wherein the measurement results include at least one of the following :
- secondary cell drops before handover,
- secondary cell drops after handover,
- secondary cell changes after handover, and
- primary cell change after handover.
According to further refinements of the invention as defined under the above aspects
- the secondary cell drops before handover are measured for each base station, carrier aggregation group and/or for each cell;
- the secondary cell drops before handover are measured based on received user equipment measurement reports from the primary cell within a configurable timer;
- the secondary cell drops after handover, the secondary cell change after handover, and/or the primary cell change after handover are measured for each base station, each carrier aggregation group, each cell, and/or for each neighbour relation;
- the secondary cell drops after handover are measured based on received user equipment measurement reports from a new primary cell within a configurable timer after receiving a successful incoming handover; - the secondary cell drops before handover and the secondary cell drops after handover are measured based on the data transmission success rate with the Scell within a configurable timer after receiving a successful incoming handover;
- the secondary cell drops after handover are measured from
RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the RRCConnectionReconfiguration message, the sCellToReleaseList is not empty, after receiving a successful incoming handover;
- the secondary cell changes after handover are measured from
RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the same or different RRCConnectionReconfiguration messages, some SCells are added and some SCells are released, after receiving a successful incoming handover;
- the primary cell change after handover is measured from
RRCConnectionReconfiguration messages sent to the user equipment within a configurable timer, while in the RRCConnectionReconfiguration message the primary cell is changed, after receiving a successful incoming handover; - the base station is s source base station configured to measure the measurement secondary cell drops before handover, and to report the measurement to an element manager in case of a centralized self
organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
- the base station is a source base station configured to measure the measurement results, and to report the measurement to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager; - the base station is a target base station configured to measure the measurement results and to report the measurement results to a source base station in case of a distributed self organizing network architecture with an X2 interface;
- the base station is a target base station configured to measure the measurement results and to report the measurement results to an element manager in case of a distributed self organizing network architecture without an X2 interface, and the element manager forwards the
measurement results to the source base station;
- the base station is a target base station configured to measure the measurement results and to report the measurement results to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager;
- the measurement results are forwarded to a network manager in case of a centralized self organizing network architecture and the self organizing network server is at network manager level;
- the measurement results are forwarded to a network manager in case of the source base station and the target base station are managed by different element managers;
- the reported measurement results are used for evaluating the handover performance, evaluating the mobile robustness optimization performance and correcting handover parameters.
According to another aspect of the present invention there is provided a computer program product comprising code means adapted to produce steps of any of the methods as described above when loaded into the memory of a computer.
According to a still further aspect of the invention there is provided a computer program product as defined above, wherein the computer program product comprises a computer-readable medium on which the software code portions are stored .
According to a still further aspect of the invention there is provided a computer program product as defined above, wherein the program is directly loadable into an internal memory of the processing device.
Brief Description of the Drawings These and other objects, features, details and advantages will become more apparent from the following detailed description of embodiments of the present invention which is to be taken in conjunction with the appended drawings, in which : Fig . 1 is a block diagram illustrating a SON architecture to which
embodiments of the present invention are applicable;
Fig . 2 is a block diagram illustrating another SON architecture to which embodiments of the present invention are applicable;
Fig . 3 is a block diagram showing a base station according to an embodiment of the present invention.
Fig . 4 is a flowchart illustrating processing of the base station 10.
Detailed Description In the following, embodiments of the present invention are described by referring to general and specific examples of the embodiments. It is to be understood, however, that the description is given by way of example only, and that the described embodiments are by no means to be understood as limiting the present invention thereto.
Figs. 1 and 2 illustrate examples of SON architectures to which
embodiments of the present invention are applicable. Fig . 1 shows a distributed architecture with an X2/lur interface that connects two eNBs (enhanced NodeB) or RNCs (radio network controller) with each other, and which are further connected to an element manager EM. The eNB can be managed by the same or different element managers.
Fig . 2 further shows an architecture which is distributed without an X2/lur interface and an centralized architecture.
In distributed SON, the SON functions are located at the eNB, and in the centralized SON, the SON functions are located at element manager, network manager (NM) or SON server.
According to certain embodiments of the present invention, it is proposed that the eNB performs measurements about the Scell drops before or after the handover, and performs measurements about Scell changes after the handover as well as measurements about the Pcell change after the handover.
1) As to the Scell drops before the handover, the eNB measures the Scell drops before the handover for each eNB, each CA group (i.e. a group of cells that can be aggregated together) and/or for each cell.
This can be measured by the eNB based on the received UE measurement reports from Pcell within a configurable timer, while in these reports the measured Scell has a poor signal (lower than a certain value or margin in average), or if data transmission success rate with this Scell is below a certain value within the configurable timer, and there is at least one cell not in this CA group which has a good signal (reaches a certain value or margin).
The information about Scell drops before HO is helpful for the source eNB to judge if the handover is too-late (for Scells).
2) As to the Scell drops after handover, the eNB measures the Scell drops after the handover for each eNB, each CA group, each cell, and/or for each neighbour relation.
The Scell drops after handover can be measured firstly at a target eNB, and the target eNB then reports the measurement results back to the source eNB (for distributed MRO architectures with X2 interface, as illustrated in Fig . 1), or report them back to the element manager (EM) (for centralized MRO architecture and distributed without X2, as illustrated in Fig. 2).
After receiving a successful incoming handover, the (target) eNB can measure the Scell drops:
a) based on the received UE measurement reports from the new Pcell within a configurable timer, while in these reports some certain assigned
Scell has a poor signal (below a certain value or margin in average); or b) if data transmission success rate with this Scell is below a certain value within the configurable timer, or
c) the (target) eNB released the Scell to the UE due to air interface quality reasons within the configurable timer.
The information about Scell drops after the handover is helpful for the source eNB to judge if the handover is too early or to wrong cells (for Scells).
3) Regarding Scell changes after the handover, the eNB measures the Scell changes after the handover for each eNB, each CA group, each cell, and/or for each neighbour relation. The Scell changes after handover can be measured firstly at target eNB, and the target eNB then reports the measurement results back to the source eNB (for distributed MRO architecture with X2, as illustrated in Fig. 1), or reports them back to the OAM (operations, administration and maintenance) (for centralized MRO architecture and distributed without X2, as illustrated in Fig. 2).
After receiving a successful incoming handover, the (target) eNB can measure the Scell changes from the RRCConnectionReconfiguration messages sent to the UE due to air interface quality reason within the configurable timer, while in the same or different
RRCConnectionReconfiguration messages, some SCells are added and some SCells are released .
The information about Scell changes after the handover is helpful for the source eNB to judge if the handover is to wrong cells (for Scells, and which should be better candidate Scells for handover). 4) As to the Pcell change after the handover, the eNB measures the Pcell change after the handover for each eNB, each CA group, each cell, and/or for each neighbour relation.
The Pcell change after handover can be measured firstly at target eNB, and the target eNB then reports the measurement results back to the source eNB (for distributed MRO architecture with X2, as illustrated in Fig. 1), or reports them back to OAM (for centralized MRO architecture and distributed without X2, as illustrated in Fig . 2). After receiving a successful incoming handover, the (target) eNB can measure the Pcell change from the RRCConnectionReconfiguration message sent to the UE within the configurable timer, while in the
RRCConnectionReconfiguration message, the Pcell is changed . The information about Pcell changes after the handover is helpful for the source eNB to judge if the handover is to an improper Pcell (and which should be better candidate Pcell for handover).
For the distributed SON architecture with X2, as illustrated in Fig . 1, the source eNB will take the reported Scell drops/changes and/or Pcell change to be part of input to correct the handover parameters. For distributed SON architecture without X2, the EM will forward the reported Scell drops/changes and/or Pcell change to the source eNB, which requires Itf-N support if the source eNB is not managed by the same EM . Then, the source eNB will take the reported Scell drops/changes and/or Pcell change to be part of input to correct the handover parameters.
For the centralized SON architecture, the EM will forward the reported Scell drops/changes and/or Pcell change to the SON server if separated, which requires Itf-N support if the SON server is at NM level. The SON server will then take the reported Scell drops/changes and/or Pcell change to be part of input to correct the handover parameters.
The timers/thresholds used for detecting the above described events may be configurable. Certain embodiments of the present invention are implemented in the eNB, EM, NM or a separate SON server.
The following examples show in the typical format of a 3GPP 32. series, 36. series and 25. series stage 2 description, how the solution according to certain embodiments of the invention can be realized . For example, in the technical specification 36.300 of 3GPP (3 generation partnership project), 3GPP TS 36.300, the following is added .
"Mobility Robustness Optimization also aims at detecting and enabling correction of the following problems in a CA scenario"
- Scell drops before handover
- Scell drops after handover
- Scell changes after handover
- Pcell change after handover
These problems are defined as stated above under items 1) to 4).
As a further example, in the 3GPP TS 36.423, the following information is added into the "Handover Report" message, which is sent by the eNB to report a handover failure event, or into a new message (like, for example, CA Handover Report) for the case of a distributed architecture with X2 only.
Figure imgf000014_0001
As a still further example, the following is added in the 3GPP TS 32.521. REQ_FUN_x: "Mobility Robustness Optimization also aims at detecting and enabling correction of the following problems in a CA scenario :
- Scell drops before handover
- Scell drops after handover
- Scell changes after handover
- Pcell change after handover As a still further example, there is created a new information object class (IOC) (e.g . HOReportlnCA) in the 3GPP TS 32.762 with the following attributes (for architecture distributed without X2/lur and centralized only).
Figure imgf000015_0001
As another example, the following targets and performance measurements are added to 3GPP TS 32.522 :
- Number of Scell drops before handover;
- Number of Scell drops after handover;
- Number of Scell changes after handover;
- Number of Pcell change after handover. Furthermore, as still another example, the following performance
measurements are added to 3GPP TS 32.425 :
- Number of Scell drops before handover, as defined under item 1) as stated above;
- Number of Scell drops after handover, as defined under item 2) as stated above;
- Number of Scell changes after handover, as defined under item 3) as stated above;
- Number of Pcell change after handover, as defined under item 4) as stated above.
Further, the following attributes are added to the EUtranGeneric CEII IOC or the EUtranRelation IOC in 3GPP TS 32.762 : Attribute Definition Legal Values
TimerForScellDropBefore Timer for detecting the Scell In ms
HO drops before HO
ThresholdForScellDropBef Absolute or relative value (to In integer
oreHO serving Pcell) of signalling
strength in db/dbm for detecting
the Scell drops before HO
DataSuccessRateForScell Data transmission success rate In percentage
DropBeforeHO for detecting Scell drops before
HO
Furthermore, the following attributes are added to the EUtranGenericCell IOC in 3GPP TS 32.762 :
Figure imgf000016_0001
Fig . 3 is a block diagram showing a base station according to an embodiment of the present invention. As shown in Fig. 3, the base station 10 comprises a measuring unit 11 and a transceiver 12 connected to the measuring unit.
Fig . 4 is a flowchart illustrating processing of the base station 10. First, in a step S21, the base station 10 measures measurement results related to the primary cell and the secondary cells. Then, in a step S22, the base station 10 forwards the measurement results to an element manager, base station or server. In the foregoing exemplary description of the base station, only the units that are relevant for understanding the principles of the invention have been described using functional blocks. The base station may comprise further units that are necessary for its respective operation. However, a description of these units is omitted in this specification. The arrangement of the functional blocks of the devices is not construed to limit the invention, and the functions may be performed by one block or further split into sub- blocks.
For the purpose of the present invention as described herein above, it should be noted that
- method steps likely to be implemented as software code portions and being run using a processor at a radio access node, element manager, network manager, SON server or user equipment (as examples of devices, apparatuses and/or modules thereof, or as examples of entities including apparatuses and/or modules therefore), are software code independent and can be specified using any known or future developed programming language as long as the functionality defined by the method steps is preserved;
- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the embodiments and its modification in terms of the functionality implemented;
- method steps and/or devices, units or means likely to be implemented as hardware components at the above-defined apparatuses, or any module(s) thereof, (e.g ., devices carrying out the functions of the apparatuses according to the embodiments as described above) are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor- Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components;
- devices, units or means (e.g . the above-defined apparatuses and user equipments, or any one of their respective units/means) can be implemented as individual devices, units or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device, unit or means is preserved;
- an apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor;
- a device may be regarded as an apparatus or as an assembly of more than one apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example.
In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.
Generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention. Devices and means can be implemented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved . Such and similar principles are to be considered as known to a skilled person.
Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof. It is noted that the embodiments and general and specific examples described above are provided for illustrative purposes only and are in no way intended that the present invention is restricted thereto. Rather, it is the intention that all variations and modifications which fall within the scope of the appended claims are covered .

Claims

1. A method in a self-organizing network, comprising :
in performing multiple-to-multiple-cell handover with carrier aggregation in a network including at least one primary cell and one or more secondary cells,
measuring, at a base station, measurement results related to the primary cell and the secondary cells,
wherein the measurement results include at least one of the following : - secondary cell drops before handover,
- secondary cell drops after handover,
- secondary cell changes after handover, and
primary cell change after handover.
2. The method according to claim 1, wherein the secondary cell drops before handover are measured for each base station, carrier aggregation group and/or for each cell .
3. The method according to claim 1 or 2, wherein the secondary cell drops before handover are measured based on received user equipment
measurement reports from the primary cell within a configurable timer.
4. The method according to claim 1, wherein the secondary cell drops after handover, the secondary cell change after handover, and/or the primary cell change after handover are measured for each base station, each carrier aggregation group, each cell, and/or for each neighbour relation.
5. The method according to claim 1 or 4, wherein the secondary cell drops after handover are measured based on received user equipment
measurement reports from a new primary cell within a configurable timer after receiving a successful incoming handover.
6. The method according to claim 1 or 4, wherein the secondary cell drops before handover and the secondary cell drops after handover are measured based on the data transmission success rate with the Scell within a configurable timer after receiving a successful incoming handover.
7. The method according to claim 1 or 4, wherein the secondary cell drops after handover are measured from RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the RRCConnectionReconfiguration message, the sCellToReleaseList is not empty, after receiving a successful incoming handover.
8. The method according to claim 1 or 4, wherein the secondary cell changes after handover are measured from RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the same or different
RRCConnectionReconfiguration messages, some SCells are added and some SCells are released, after receiving a successful incoming handover.
9. The method according to claim 1 or 4, wherein the primary cell change after handover is measured from RRCConnectionReconfiguration messages sent to the user equipment within a configurable timer, while in the
RRCConnectionReconfiguration message the primary cell is changed, after receiving a successful incoming handover.
10. The method according to claim 1, wherein the measurement secondary cell drops before handover are measured at a source base station, and reported to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager.
11. The method according to any one of claims 2 to 3, wherein the measurement results are measured at a source base station, and reported to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager.
12. The method according to any one of claims 4 to 9, wherein the measurement results are measured at a target base station and reported to a source base station in case of a distributed self organizing network architecture with an X2 interface.
13. The method according to any one of claims 4 to 9, wherein the measurement results are measured at a target base station and reported to an element manager in case of a distributed self organizing network architecture without an X2 interface, and the element manager forwards the measurement results to the source base station.
14. The method according to any one of claims 4 to 7, wherein the measurement results are measured at a target base station and reported to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager.
15. The method according to claim 10, 11 or 14, wherein the measurement results are forwarded to a network manager in case of a centralized self organizing network architecture and the self organizing network server is at network manager level .
16. The method according to claim 13, wherein the measurement results are forwarded to a network manager in case of the source base station and the target base station are managed by different element managers.
17. The method according to any one of claims 1 to 16, wherein the reported measurement results are used for evaluating the handover performance, evaluating the mobile robustness optimization performance and correcting handover parameters.
18. A base station in a self-organizing network, comprising :
in performing multiple-to-multiple-cell handover with carrier aggregation in a network including at least one primary cell and one or more secondary cells,
a measuring unit configured to measure measurement results related to the primary cell and the secondary cells,
wherein the measurement results include at least one of the following :
- secondary cell drops before handover,
- secondary cell drops after handover,
- secondary cell changes after handover, and
primary cell change after handover.
19. The base station according to claim 18, wherein the secondary cell drops before handover are measured for each base station, carrier
aggregation group and/or for each cell.
20. The base station according to claim 18 or 19, wherein the secondary cell drops before handover are measured based on received user equipment measurement reports from the primary cell within a configurable timer.
21. The base station according to claim 18, wherein the secondary cell drops after handover, the secondary cell change after handover, and/or the primary cell change after handover are measured for each base station, each carrier aggregation group, each cell, and/or for each neighbour relation.
22. The base station according to claim 18 or 21, wherein the secondary cell drops after handover are measured based on received user equipment measurement reports from a new primary cell within a configurable timer after receiving a successful incoming handover.
23. The base station according to claim 18 or 21, wherein the secondary cell drops before handover and the secondary cell drops after handover are measured based on the data transmission success rate with the Scell within a configurable timer after receiving a successful incoming handover.
24. The base station according to claim 18 or 21, wherein the secondary cell drops after handover are measured from RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the RRCConnectionReconfiguration message, the sCellToReleaseList is not empty, after receiving a successful incoming handover.
25. The base station according claim 18 or 21, wherein the secondary cell changes after handover are measured from RRCConnectionReconfiguration messages sent to the user equipment due to air interface quality reason within the configurable timer, while in the same or different
RRCConnectionReconfiguration messages, some SCells are added and some SCells are released, after receiving a successful incoming handover.
26. The base station according to claim 18 or 21, wherein the primary cell change after handover is measured from RRCConnectionReconfiguration messages sent to the user equipment within a configurable timer, while in the RRCConnectionReconfiguration message the primary cell is changed, after receiving a successful incoming handover.
27. The base station according to claim 18, wherein the base station is s source base station configured to measure the measurement secondary cell drops before handover, and to report the measurement to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager.
28. The base station according to any one of claims 19 to 20, wherein the base station is a source base station configured to measure the measurement results, and to report the measurement to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager.
29. The base station according to any one of claims 21 to 24, wherein the base station is a target base station configured to measure the
measurement results and to report the measurement results to a source base station in case of a distributed self organizing network architecture with an X2 interface.
30. The base station according to any one of claims 21 to 24, wherein the base station is a target base station configured to measure the
measurement results and to report the measurement results to an element manager in case of a distributed self organizing network architecture without an X2 interface, and the element manager forwards the
measurement results to the source base station.
31. The base station according to any one of claims 21 to 24, wherein the base station is a target base station configured to measure the
measurement results and to report the measurement results to an element manager in case of a centralized self organizing network architecture, and the element manager forwards the measurement results to a self organizing network server if the self organizing network server is separated from the element manager.
32. The base station according to claim 27, 28 or 31, wherein the
measurement results are forwarded to a network manager in case of a centralized self organizing network architecture and the self organizing network server is at network manager level.
33. The base station according to claim 30, wherein the measurement results are forwarded to a network manager in case of the source base station and the target base station are managed by different element managers.
34. The base station according to any one of claims 18 to 33, wherein the reported measurement results are used for evaluating the handover performance, evaluating the mobile robustness optimization performance and correcting handover parameters.
35. A computer program product including a program for a processing device, comprising software code portions for performing the steps of any one of claims 1 to 17 when the program is run on the processing device.
36. The computer program product according to claim 35, wherein the computer program product comprises a computer-readable medium on which the software code portions are stored.
37. The computer program product according to claim 35, wherein the program is directly loadable into an internal memory of the processing device.
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