Method and apparatus for transmitting user equipment group information in wireless communication system
09749910 · 2017-08-29
Assignee
Inventors
Cpc classification
H04W36/0083
ELECTRICITY
H04W36/0009
ELECTRICITY
International classification
Abstract
A method and apparatus for transmitting user equipment (UE) group information in a wireless communication system is provided. A source eNodeB (eNB) of a handover procedure transmits a handover request message including UE group information to a target eNB of the handover procedure when the source eNB hands over a UE to the target eNB. The UE group information is included in a UE history information IE (information element) of the handover request message.
Claims
1. A method for transmitting, by a source eNodeB (eNB) of a handover procedure, user equipment (UE) group information in a wireless communication system, the method comprising: determining whether a ping-pong event is detected during the handover procedure, wherein the ping-pong event specifies that a UE is handed over from a target eNB to the source eNB, after the UE is handed over from the source eNB to the target eNB; if the ping-pong event is detected, transmitting a handover request message including the UE group information indicating a group, to which UEs concerned with the ping-pong event belong, to the target eNB, wherein the UE group information is included in a UE history information IE (information element) of the handover request message, wherein the UE group information indicates the group of the UEs to be applied different handover parameters during the handover procedure to avoid the ping-pong event between the source eNB and the target eNB.
2. The method of claim 1, wherein the UE group information is forwarded, by the target eNB, to another target eNB of next handover procedure.
3. The method of claim 1, wherein the UE group information includes whether the UE is served with cell range expansion (CRE) or not in a cell of the source eNB.
4. The method of claim 1, wherein the UE group information includes whether the UE is moving with high speed, medium speed or low speed.
5. The method of claim 1, wherein the UE group information includes whether the UE is served real time (RT) traffics or not.
6. The method of claim 1, wherein the UE group information includes whether in-device coexistence (IDC) problems of the UE can be solved in a cell of the source eNB.
7. A source eNodeB (eNB) of a handover procedure in a wireless communication system, the source eNB comprising: a radio frequency (RF) unit for transmitting or receiving a radio signal; and a processor coupled to the RF unit, and configured to: determine whether a ping-pong event is detected during the handover procedure, wherein the ping-pong event specifies that a user equipment (UE) is handed over from a target eNB to the source eNB, after the UE is handed over from the source eNB to the target eNB; if the ping-pong event is detected, transmit a handover request message including user equipment (UE) group information indicating a group, to which UEs concerned with the ping-pong event belong, to the target eNB, wherein the UE group information is included in a UE history information IE (information element) of the handover request message, wherein the UE group information indicates the group of the UEs to be applied different handover parameters during the handover procedure to avoid the ping-pong event between the source eNB and the target eNB.
8. The source eNB of claim 7, wherein the UE group information is forwarded, by the target eNB, to another target eNB of next handover procedure.
9. The source eNB of claim 7, wherein the UE group information includes whether the UE is served with cell range expansion (CRE) or not in a cell of the source eNB.
10. The source eNB of claim 7, wherein the UE group information includes whether the UE is moving with high speed, medium speed or low speed.
11. The source eNB of claim 7, wherein the UE group information includes whether the UE is served real time (RT) traffics or not.
12. The source eNB of claim 7, wherein the UE group information includes whether in-device coexistence (IDC) problems of the UE can be solved in a cell of the source eNB.
13. A method for transmitting, by an eNodeB (eNB), user equipment (UE) group information in a wireless communication system, the method comprising: determining whether a Radio Link Failure (RLF) is detected during a handover procedure, wherein the RLF occurs when the handover procedure occurs at a wrong time or when the handover procedure is a handoff to a wrong cell; if the RLF is detected, transmitting the UE group information indicating a group, to which UEs concerned with the RLF belong, to a target eNB of the handover procedure, wherein the UEs concerned with the RLF are categorized by handling in the target eNB, wherein the UE group information indicates the group of the UEs to be applied different handover parameters during the handover procedure to avoid the RLF with the target eNB.
14. The method of claim 13, wherein the UE group information is included in an RLF indication message.
15. The method of claim 14, wherein the eNB is an eNB that the UE reestablishes after the RLF has occurred.
16. The method of claim 13, wherein the UE group information is included in a handover report message.
17. The method of claim 16, wherein the eNB is an eNB that the RLF has occurred.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DESCRIPTION OF EXEMPLARY EMBODIMENTS
(10) The technology described below can be used in various wireless communication systems such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), etc. The CDMA can be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA-2000. The TDMA can be implemented with a radio technology such as global system for mobile communications (GSM)/general packet ratio service (GPRS)/enhanced data rate for GSM evolution (EDGE). The OFDMA can be implemented with a radio technology such as institute of electrical and electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), etc. IEEE 802.16m is an evolution of IEEE 802.16e, and provides backward compatibility with an IEEE 802.16-based system. The UTRA is a part of a universal mobile telecommunication system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of an evolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA in downlink and uses the SC-FDMA in uplink. LTE-advance (LTE-A) is an evolution of the 3GPP LTE.
(11) For clarity, the following description will focus on the LTE-A. However, technical features of the present invention are not limited thereto.
(12) Handover (HO) is described. It may be referred to Section 10.1.2.1 of 3GPP TS 36.300 V11.4.0 (2012-12).
(13) The intra E-UTRAN HO of a UE in RRC CONNECTED state is a UE-assisted network-controlled HO, with HO preparation signaling in E-UTRAN: Part of the HO command comes from the target eNB and is transparently forwarded to the UE by the source eNB; To prepare the HO, the source eNB passes all necessary information to the target eNB (e.g., E-UTRAN radio access bearer (E-RAB) attributes and RRC context): When carrier aggregation (CA) is configured and to enable secondary cell (SCell) selection in the target eNB, the source eNB can provide in decreasing order of radio quality a list of the best cells and optionally measurement result of the cells. Both the source eNB and UE keep some context (e.g., cell radio network temporary identifier (C-RNTI)) to enable the return of the UE in case of HO failure; UE accesses the target cell via RACH following a contention-free procedure using a dedicated RACH preamble or following a contention-based procedure if dedicated RACH preambles are not available: the UE uses the dedicated preamble until the handover procedure is finished (successfully or unsuccessfully); If the RACH procedure towards the target cell is not successful within a certain time, the UE initiates radio link failure recovery using the best cell; No robust header compression (ROHC) context is transferred at handover.
(14) The preparation and execution phase of the HO procedure is performed without EPC involvement, i.e., preparation messages are directly exchanged between the eNBs. The release of the resources at the source side during the HO completion phase is triggered by the eNB. In case an RN is involved, its donor eNB (DeNB) relays the appropriate S1 messages between the RN and the MME (S1-based handover) and X2 messages between the RN and target eNB (X2-based handover); the DeNB is explicitly aware of a UE attached to the RN due to the S1 proxy and X2 proxy functionality.
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(16) 0. The UE context within the source eNB contains information regarding roaming restrictions which were provided either at connection establishment or at the last timing advance (TA) update.
(17) 1. The source eNB configures the UE measurement procedures according to the area restriction information. Measurements provided by the source eNB may assist the function controlling the UE's connection mobility.
(18) 2. The UE is triggered to send measurement reports by the rules set by i.e., system information, specification, etc.
(19) 3. The source eNB makes decision based on measurement reports and radio resource management (RRM) information to hand off the UE.
(20) 4. The source eNB issues a handover request message to the target eNB passing necessary information to prepare the HO at the target side (UE X2 signalling context reference at source eNB, UE S1 EPC signalling context reference, target cell identifier (ID), K.sub.eNB*, RRC context including the C-RNTI of the UE in the source eNB, AS-configuration, E-RAB context and physical layer ID of the source cell+short MAC-I for possible radio link failure (RLF) recovery). UE X2/UE S1 signalling references enable the target eNB to address the source eNB and the EPC. The E-RAB context includes necessary radio network layer (RNL) and transport network layer (TNL) addressing information, and quality of service (QoS) profiles of the E-RABs.
(21) 5. Admission Control may be performed by the target eNB dependent on the received E-RAB QoS information to increase the likelihood of a successful HO, if the resources can be granted by target eNB. The target eNB configures the required resources according to the received E-RAB QoS information and reserves a C-RNTI and optionally a RACH preamble.
(22) The AS-configuration to be used in the target cell can either be specified independently (i.e., an “establishment”) or as a delta compared to the AS-configuration used in the source cell (i.e., a “reconfiguration”).
(23) 6. The target eNB prepares HO with L1/L2 and sends the handover request acknowledge to the source eNB. The handover request acknowledge message includes a transparent container to be sent to the UE as an RRC message to perform the handover. The container includes a new C-RNTI, target eNB security algorithm identifiers for the selected security algorithms, may include a dedicated RACH preamble, and possibly some other parameters, i.e., access parameters, SIBs, etc. The handover request acknowledge message may also include RNL/TNL information for the forwarding tunnels, if necessary.
(24) As soon as the source eNB receives the handover request acknowledge, or as soon as the transmission of the handover command is initiated in the downlink, data forwarding may be initiated.
(25) Steps 7 to 16 in
(26) 7. The target eNB generates the RRC message to perform the handover, i.e., RRCConnectionReconfiguration message including the mobilityControlInformation, to be sent by the source eNB towards the UE. The source eNB performs the necessary integrity protection and ciphering of the message. The UE receives the RRCConnectionReconfiguration message with necessary parameters (i.e. new C-RNTI, target eNB security algorithm identifiers, and optionally dedicated RACH preamble, target eNB SIBs, etc.) and is commanded by the source eNB to perform the HO. The UE does not need to delay the handover execution for delivering the HARQ/ARQ responses to source eNB.
(27) 8. The source eNB sends the sequence number (SN) status transfer message to the target eNB to convey the uplink PDCP SN receiver status and the downlink PDCP SN transmitter status of E-RABs for which PDCP status preservation applies (i.e., for RLC AM). The uplink PDCP SN receiver status includes at least the PDCP SN of the first missing UL service data unit (SDU) and may include a bit map of the receive status of the out of sequence UL SDUs that the UE needs to retransmit in the target cell, if there are any such SDUs. The downlink PDCP SN transmitter status indicates the next PDCP SN that the target eNB shall assign to new SDUs, not having a PDCP SN yet. The source eNB may omit sending this message if none of the E-RABs of the UE shall be treated with PDCP status preservation.
(28) 9. After receiving the RRCConnectionReconfiguration message including the mobilityControlInformation, UE performs synchronization to target eNB and accesses the target cell via RACH, following a contention-free procedure if a dedicated RACH preamble was indicated in the mobilityControlInformation, or following a contention-based procedure if no dedicated preamble was indicated. UE derives target eNB specific keys and configures the selected security algorithms to be used in the target cell.
(29) 10. The target eNB responds with UL allocation and timing advance.
(30) 11. When the UE has successfully accessed the target cell, the UE sends the RRCConnectionReconfigurationComplete message (C-RNTI) to confirm the handover, along with an uplink buffer status report, whenever possible, to the target eNB to indicate that the handover procedure is completed for the UE. The target eNB verifies the C-RNTI sent in the RRCConnectionReconfigurationComplete message. The target eNB can now begin sending data to the UE.
(31) 12. The target eNB sends a path switch request message to MME to inform that the UE has changed cell.
(32) 13. The MME sends a modify bearer request message to the serving gateway.
(33) 14. The serving gateway switches the downlink data path to the target side. The Serving gateway sends one or more “end marker” packets on the old path to the source eNB and then can release any U-plane/TNL resources towards the source eNB.
(34) 15. The serving gateway sends a modify bearer response message to MME.
(35) 16. The MME confirms the path switch request message with the path switch request acknowledge message.
(36) 17. By sending the UE context release message, the target eNB informs success of HO to source eNB and triggers the release of resources by the source eNB. The target eNB sends this message after the path switch request acknowledge message is received from the MME.
(37) 18. Upon reception of the UE context release message, the source eNB can release radio and C-plane related resources associated to the UE context. Any ongoing data forwarding may continue.
(38) A handover preparation procedure is described. It may be referred to Section 8.2.1 of 3GPP TS 36.423 V11.5.0 (2013-06). This procedure is used to establish necessary resources in an eNB for an incoming handover. The procedure uses UE-associated signaling.
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(40) If at least one of the requested non-guaranteed bit rate (GBR) E-RABs is admitted to the cell indicated by the Target Cell ID IE, the target eNB shall reserve necessary resources, and in step S71, send the HANDOVER REQUEST ACKNOWLEDGE message back to the source eNB. The target eNB shall include the E-RABs for which resources have been prepared at the target cell in the E-RABs Admitted List IE. The target eNB shall include the E-RABs that have not been admitted in the E-RABs Not Admitted List IE with an appropriate cause value.
(41) At reception of the HANDOVER REQUEST message the target eNB shall prepare the configuration of the AS security relation between the UE and the target eNB by using the information in the UE Security Capabilities IE and the AS Security Information IE in the UE Context Information IE.
(42) For each E-RAB for which the source eNB proposes to do forwarding of downlink data, the source eNB shall include the DL Forwarding IE within the E-RABs To be Setup Item IE of the HANDOVER REQUEST message. For each E-RAB that it has decided to admit, the target eNB may include the DL GTP Tunnel Endpoint IE within the E-RABs Admitted Item IE of the HANDOVER REQUEST ACKNOWLEDGE message to indicate that it accepts the proposed forwarding of downlink data for this bearer. This GTP tunnel endpoint may be different from the corresponding GTP TEID IE in the E-RAB To Be Switched in Downlink List IE of the PATH SWITCH REQUEST message depending on implementation choice.
(43) For each bearer in the E-RABs Admitted List IE, the target eNB may include the UL GTP Tunnel Endpoint IE to indicate that it requests data forwarding of uplink packets to be performed for that bearer.
(44) Upon reception of the HANDOVER REQUEST ACKNOWLEDGE message the source eNB shall stop the timer T.sub.RELOCprep, start the timer TX2.sub.RELocoverall and terminate the handover preparation procedure. The source eNB is then defined to have a prepared Handover for that X2 UE-associated signaling.
(45) Upon reception of UE History Information IE in the HANDOVER REQUEST message, the target eNB shall collect the information defined as mandatory in the UE History
(46) Information IE and shall, if supported, collect the information defined as optional in the UE History Information IE, for as long as the UE stays in one of its cells, and store the collected information to be used for future handover preparations.
(47) Table 1 shows an example of the HANDOVER REQUEST message. It may be referred to Section 9.1.1.1 of 3GPP TS 36.423 V11.5.0 (2013-06). This message is sent by the source eNB to the target eNB to request the preparation of resources for a handover.
(48) TABLE-US-00001 TABLE 1 IE type and Semantics Assigned IE/Group Name Presence Range reference description Criticality Criticality Message Type M 9.2.13 YES reject Old eNB UE X2AP M eNB UE Allocated at YES reject ID X2AP ID the source 9.2.24 eNB Cause M 9.2.6 YES ignore Target Cell ID M ECGI YES reject 9.2.14 GUMMEI M 9.2.16 YES reject UE Context 1 YES reject Information >MME UE S1AP M INTEGER MME UE — — ID (0 . . . 2.sup.32-1) S1AP ID allocated at the MME >UE Security M 9.2.29 — — Capabilities >AS Security M 9.2.30 — — Information >UE Aggregate M 9.2.12 — — Maximum Bit Rate >Subscriber Profile O 9.2.25 — — ID for RAT/ Frequency priority >E-RABs To Be 1 — — Setup List >>E-RABs To Be 1 . . . <maxnoof Bearers> EACH ignore Setup Item >>>E-RAB ID M 9.2.23 — — >>>E-RAB Level M 9.2.9 Includes — — QoS Parameters necessary QoS parameters >>>DL Forwarding O 9.2.5 — — >>>UL GTP Tunnel M GTP Tunnel SGW endpoint — — Endpoint Endpoint of the S1 9.2.1 transport bearer. For delivery of ULPDUs. >RRC Context M OCTET Includes the — — STRING RRC Handover Preparation Information message as defined in subclause 10.2.2 of TS 36.331 [9] >Handover O 9.2.3 — — Restriction List >Location Reporting O 9.2.21 Includes the — — Information necessary parameters for location reporting >Management Based O 9.2.59 YES ignore MDT Allowed >Management Based O MDT PLMN YES ignore MDT PLMN List List 9.2.64 UE History M 9.2.38 Same definition YES ignore Information as in TS 36.413 [4] Trace Activation O 9.2.2 YES ignore SRVCC Operation O 9.2.33 YES ignore Possible CSG Membership O 9.2.52 YES reject Status Mobility Information O BIT Information YES ignore STRING related to the (SIZE (32)) handover; the source eNB provides it in order to enable later analysis of the conditions that led to a wrong HO.
(49) Referring to Table 1, the HANDOVER REQUEST message includes the UE History Information IE as mandatory.
(50) Table 2 shows an example of the UE History Information IE. It may be referred to Section 9.2.38 of 3GPP TS 36.423 V11.5.0 (2013-06). The UE History Information IE contains information about cells that a UE has been served by in active state prior to the target cell.
(51) TABLE-US-00002 TABLE 2 IE type and Semantics Assigned IE/Group Name Presence Range reference description Criticality Criticality Last Visited Cell 1 . . . <maxnoofCells> Most recent — — List information is added to the top of this list >Last Visited Cell M 9.2.39 — — Information
(52) Mobility setting change procedure is described. It may be referred to Section 8.3.8 of 3GPP TS 36.423 V11.5.0 (2013-06). This procedure enables an eNB to negotiate the handover trigger settings with a peer eNB controlling neighboring cells. The procedure uses non UE-associated signaling.
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(54) In order to improve mobility load balancing (MLB) and mobility robustness optimization (MRO) functions, the 3GPP LTE plans to consider UE grouping. The following scenarios have been discussed regarding the UE grouping issue.
(55) According to current specifications, differentiation of mobility settings is possible. The objective of the “SON for UE types” task should be to evaluate if differentiation of mobility settings mechanisms can cause interoperability issue. If differentiation of mobility settings mechanisms causes interoperability issue, solutions for them has to be evaluated. Any solution should bring sufficient improvements to inter vendor interoperability and it should be robust. Such solutions should not unnecessarily limit the flexibility available in current systems for assigning different policies to UEs or UE groups.
(56) Enabling wider differentiation of mobility setting may be needed in the system (homogeneous and heterogeneous scenarios), but may create issues, such as ping-pong event. Example scenarios of the ping-pong event are described as follows. When load balancing is used to resolve congestion in the source cell, and the mobility settings change procedure is used to adapt the handover trigger point to the target cell, some UE categories may be subject to ping-pong depending on how the UE category is handled in the target cell. A UE belonging to such UE category is handed over from the congested source cell to the target cell while located far out in the edge of the target cell. While the eNB serving the target cell is aware that handing over the UE back to the congested cell within a certain time window causes a ping pong event, whether the eNB serving the target cell needs additional information for further handover decisions has not yet defined. These decisions are typically based on a trade-off between the risk for failure and ping-pong event.
(57) Meanwhile, the way the mobility setting change procedure is defined allows for very different implementations, and such different implementations may reduce the available range for the negotiation. To depict it, the following example may be considered. It is assumed that there are two eNBs, which are eNB A, whose vendor considers the procedure as “advisory” and relies on its implementation, and eNB B where the procedure is considered binding and where the mobility decisions are made according to the agreed mobility settings. If the two eNBs are to negotiate the mobility setting, the eNB A may propose rather big changes, assuming that if there is a UE that cannot handle such a big extensions, the mobility implementation will hand over the UE sooner. Despite the fact that the specifications do not mandate to apply the negotiated handover to all UEs, the eNB B may reject such a request because some of its served UEs may not be able to handle it. And, since the standard states that eNB A should consider the response before executing the planned change, the available range for the load balancing may be reduced.
(58) Considering the scenarios described above, ping-pong detection and link failure (or handover failure) detection can be a problem. That is, while the source eNB distinguishes UEs of each group and manages them differently (e.g., adopting different handover parameters for different group of UEs), the source eNB cannot recognize the group of the UEs concerned when it detects ping-pong and link failure (or handover failure) problems of UEs. Therefore, the source eNB is not able to decide the UE group which needs to be modified managing strategies (such as handover parameters).
(59) In order to solve the problems described above, a method for transmitting UE group information according to an embodiment of the present invention is described. At first, a solution for ping-pong problem is described. In the ping-pong problem, shortly after the UE is handed over from eNB1's cell 1 to eNB2's cell 2, the UE is handed over to eNB1's cell 1. In order to make the eNB1 recognize the group of UE concerned when it detects the ping-pong problem of the UE, a method for transmitting UE group information according to an embodiment of the present invention may be proposed.
(60)
(61) The UE group information may contain the following information about each concerned UE. Whether the UE is served with cell range expansion (CRE) or not in the source cell when the UE is handed over from the source cell to the target cell Whether the UE is moving with high speed, medium speed or low speed when the UE is handed over from the source cell to the target cell (or, whether the UE was moving with high speed or low speed when the UE is handed over from the source cell to the target cell) Whether the UE is served real time (RT) traffics or not when the UE is handed over from the source cell to the target cell Whether in-device coexistence (IDC) problems of the UE can be solved in the source cell or not when the UE is handed over from the source cell to the target cell
(62) Hereinafter, a solution for link failure (or handover failure) problem is described. One of the functions of MRO is to detect connection failures that occur due to “Too early handover” or “Too late handover”, or “Handover to wrong cell”. These problems are defined as follows: Too early handover: An radio link failure (RLF) occurs shortly after a successful handover from a source cell to a target cell or a handover failure occurs during the handover procedure. The UE attempts to re-establish the radio link connection in the source cell. Too late handover: An RLF occurs after the UE has stayed for a long period of time in the cell. The UE attempts to re-establish the radio link connection in a different cell. Handover to wrong cell: An RLF occurs shortly after a successful handover from a source cell to a target cell or a handover failure occurs during the handover procedure. The UE attempts to re-establish the radio link connection in a cell other than the source cell and the target cell.
(63) For three RLF cases, in order to make the source eNB recognize the group of UE concerned when it detects the RLF problem of UE, a method for transmitting UE group information according to an embodiment of the present invention may be proposed.
(64) According to an embodiment of the present invention, the source eNB may include UE group information in the HANDOVER REQUEST message when the source eNB hands over the UE to the target eNB.
(65) Alternatively, the UE may include UE group information in the RLF report message. In this case, the UE group information may indicate the group categorized when the UE was handed over from the source eNB.
(66) Alternatively, the eNB that the UE reestablishes or establishes after RLF event includes UE group information in the RLF INDICATION message which is sent to the eNB that RLF occurred. In this case, the UE group information may indicate the group categorized when the UE was handed over from the source eNB.
(67) Alternatively, the eNB that UE's RLF occurred includes UE group information in the HANDOVER REPORT message which is sent to the source eNB. In this case, the UE group information may indicate the group categorized when the UE was handed over from the source eNB.
(68) The UE group information may contain the following information about each concerned UE. Whether the UE is served with CRE or not in the source cell when the UE is handed over from the source cell to the target cell Whether the UE is moving with high speed, medium speed or low speed when the UE is handed over from the source cell to the target cell (or, whether the UE was moving with high speed or low speed when the UE is handed over from the source cell to the target cell) Whether the UE is served RT traffics or not when the UE is handed over from the source cell to the target cell Whether IDC problems of the UE can be solved in the source cell or not when the UE is handed over from the source cell to the target cell
(69)
(70) A source eNB 800 includes a processor 810, a memory 820, and a radio frequency (RF) unit 830. The processor 810 may be configured to implement proposed functions, procedures, and/or methods in this description. Layers of the radio interface protocol may be implemented in the processor 810. The memory 820 is operatively coupled with the processor 810 and stores a variety of information to operate the processor 810. The RF unit 830 is operatively coupled with the processor 810, and transmits and/or receives a radio signal.
(71) A target eNB 900 includes a processor 910, a memory 920 and an RF unit 930. The processor 910 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor 910. The memory 920 is operatively coupled with the processor 910 and stores a variety of information to operate the processor 910. The RF unit 930 is operatively coupled with the processor 910, and transmits and/or receives a radio signal.
(72) The processors 810, 910 may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The memories 820, 920 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. The RF units 830, 930 may include baseband circuitry to process radio frequency signals. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in memories 820, 920 and executed by processors 810, 910. The memories 820, 920 can be implemented within the processors 810, 910 or external to the processors 810, 910 in which case those can be communicatively coupled to the processors 810, 910 via various means as is known in the art.
(73) According to the present invention, the source eNB can recognize the group of the UE concerned when the source eNB detects the ping-pong problem or link failure (or handover failure) problem of UE.
(74) In view of the exemplary systems described herein, methodologies that may be implemented in accordance with the disclosed subject matter have been described with reference to several flow diagrams. While for purposed of simplicity, the methodologies are shown and described as a series of steps or blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the order of the steps or blocks, as some steps may occur in different orders or concurrently with other steps from what is depicted and described herein. Moreover, one skilled in the art would understand that the steps illustrated in the flow diagram are not exclusive and other steps may be included or one or more of the steps in the example flow diagram may be deleted without affecting the scope and spirit of the present disclosure.