KR20140102555A - SYSTEM AND METHOD FOR IDENTIFYING TARGET DeNB CELL - Google Patents

Abstract

Disclosed are a system and a method to identify a target DeNB cell to hand over to the target DeNB cell during an in-band operation of a 3^rd generation partnership project (3GPP) REL-12 mobile relay node. According to the present invention, the system to identify a target DeNB cell comprises the following: a plurality of donor DeNBs located on a predetermined track through which a mobile object moves, and operating to set a downlink backhaul subframe to avoid self-interference with an uplink subframe based on downlink subframe offset information previously configured for wireless frame synchronization; a relay node operation and management server operating to transmit cell list information corresponding to the plurality of donor DeNBs; and a mobile relay node operated in an in-band way, performing cell camping on a cell of a first donor DeNB based on the cell list information, and identifying a cell of a second donor DeNB to hand over from the first donor DeNB.

Description

[0001] SYSTEM AND METHOD FOR IDENTIFYING TARGET [0002]

The present invention relates to a mobile communication system, and more particularly, to a handover to a target base station cell (target DeNB cell) in an inband operation of a 3rd generation partnership project (REL-12) mobile relay node To a target base station cell identification system and method.

"This study was conducted as a result of the study of the technology development project of the next generation communication network of the Korea Communications Commission" (KCA-2012-10911-04002)

3GPP (3rd Generation Partnership Project) Standardization of Inband Fixed Relay Node in REL-10 standard has been completed. Meanwhile, research on mobile relays has been started in the 3GPP REL-11 standard, and it is expected that the standardization of the mobile relay node (M-RN) is completed in the REL-12 standard.

It is assumed that the deployment of M-RN assumed in 3GPP operates on high-speed trains such as TGV, Shinkansen, etc. moving at a speed of 300 Km or more in a predetermined orbit, and in particular, in-band operation of M- A method for providing mobility between a plurality of DeNB cells already installed on a railway track has been studied.

Korean Patent Laid-Open Publication No. 10-2012-0018299 (published on Mar. 2, 2012) Korean Patent Application Laid-Open Publication No. US2011 / 0310753 A1 (Dec. 22, 2011)

Vehicular Technology Conference (VTC Fall), 2012 IEEE: Mobile relay based fast handover scheme in high-speed mobile environment

The present invention relates to a method and apparatus for handover to a new DeNB cell on a backhaul link when a mobile relay node is moved when a 3rd generation partnership project (3GPP) REL-12 mobile relay node is operated as an in- A new base station cell identification system and method for identifying a new DeNB (donor eNB) cell in a backhaul link with minimal impact on an access link operating at the same frequency.

The target base station cell identification system according to the present invention is located on a predetermined orbit on which a moving body moves and calculates a sub-frame of an uplink and a self interference (SI) based on predetermined downlink sub-frame offset information for radio frame synchronization A plurality of donor base stations operable to establish a downlink backhaul subframe to avoid; A relay node operation management server operable to transmit cell list information corresponding to the plurality of donor base stations; And performing cell camping of cells of a first donor base station based on the cell list information and performing cell camping of cells of the first donor base station based on the downlink backhaul subframe provided from the first donor base station, And a mobile relay node operative to identify a cell of a second donor base station for handover from the cell.

Also, a method for identifying a target base station cell according to the present invention includes the steps of: a) performing cell camping of cells of a first donor base station on the basis of cell list information of a plurality of donor base stations located on a predetermined orbit on which a mobile body moves; ; And b) a downlink backhaul subframe configured to avoid uplink subframe and SI based on downlink subframe offset information for radio frame synchronization between adjacent donor base stations, And identifying the cell of the second donor base station for handover from the second donor base station.

The present invention relates to an apparatus and method for managing a DeNB cell in an X2 setup procedure so that a donor eNB (DeNB) supporting a mobile relay node (M-RN) A downlink backhaul subframe including subframes sf # 0 and sf # 5 of a new DeNB cell is allocated when a downlink backhaul subframe is allocated to an M-RN by exchanging downlink subframe offset information, Cells can be identified.

Figure 1 is an exemplary view illustrating a downlink backhaul subframe pattern and an uplink backhaul subframe for in-band operation.
Figure 2 is an exemplary view showing a REL-10 X2-AP (X2 Application Protocol) "LOAD INDICATION" message.
Figure 3 is an exemplary view showing a REL-10 X2-AP "X2 Setup Request"message;
Figure 4 is an example of mobility support for a mobile relay node;
5 illustrates an example of a target DeNB cell identification using a subframe shifting between inter DeNBs according to an embodiment of the present invention.
FIG. 6 is an exemplary view showing an "X2 setup request" message or an "eNB configuration update" message of a REL-12 X2-AP according to an embodiment of the present invention;

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, well-known functions and configurations will not be described in detail if they obscure the subject matter of the present invention.

3GPP (3rd Generation Partnership Project) Standardization of Inband Fixed Relay Node in REL-10 standard has been completed. In order to operate as a relay node (hereinafter, referred to as RN) as an inband, a TDM (Time Division Multiplexing) that distinguishes subframes that can be used for transmission and reception between Un interface and Uu interface It is required to avoid SI (Self Interference) in the RN. Herein, the Un interface is an interface between a Donor Evolved NodeB (DeNB) and an RN on a backhaul link, and a Uu interface is a user equipment (UE) under an RN and an RN cell on an access link. Where the backhaul link is the radio link between the DeNB and the RN and the access link is the radio link between the RN and the user equipment (UE) under the RN cell.

To avoid SI, the RN receives a DeNB cell list from the RN operation and management server in the UE mode at the time of power on and camps in the DeNB cell from the RRC_IDLE. )do. Here, cell camping refers to performing a cell selection procedure or a cell selection procedure (cell selection / reselection) and selecting a cell. At this time, the RN obtains the time synchronization for the DeNB cell through the PSS (Primary Synchronization Signal), SSS (Secondary Synchronization Signal) and MIB (Master Information Block) of the DeNB cell and then sets the RRC connection And a downlink backhaul subframe (DL BHSF) pattern to be used on the backhaul link for TDM is received from the DeNB.

A, DL BHSF 8 bits transmitted based on the 8ms DL Un HARQ RTT (Downlink Un Hybrid Automatic Repeat Request Round Trip Time) from the DeNB, as shown in Figure 1, the DeNB under the RN number of the ²⁸ patterns with the 40ms period And semi-statistic according to the number of active UEs under each RN. On the other hand, the uplink backhaul subframe (UL BHSF) pattern is implicitly set between two nodes without explicit signaling to the corresponding DL BHSF + 4. The DL BHSF thus determined is transmitted to the RN through the RRC RN Reconfiguration message. At this time, the DL BHSF is set as an MBSFN (Multicast Broadcast Single Frequency Network) on the access link. Therefore, the UEs under the RN cell do not perform any reception on the corresponding part using the fact that the CRS does not exist in the data part of the MBSFN subframe, thereby preventing measurement errors for the corresponding cell, It is possible to prevent a problem in radio quality evaluation, and at the same time, the RN can receive downlink backhaul data from the DeNB without SI.

Since the inband fixed RN is a fixed relay node, mobility in the RRC_Connected state is not required as in a general UE, but when a problem occurs on the backhaul link during the initial camping or operation of the DeNB cell (Re) selection is required for the DeNB cell in RRC_IDLE. Upon re-selection for a DeNB cell, the services for the UEs under the fixed RN cell are discontinued, and a "RN reconfiguration" message for DL BHSF establishment in succession to (re) selection success on the backhaul link The service is resumed.

The CQI (Channel Quality Indicator) and the SRS (Session Relay Server) for the backhaul link use the aperiodic reporting mode in the REL-10 specification due to the discontinuous UL BHSF, and the CCH (Control Channel Element) Due to the excluded R-PDCCH signaling scheme, HARQ (Hybrid Automatic Repeat reQuest feedback) for downlink backhaul data reception is transmitted through a fixed PUCCH (Physical Uplink Control Channel) resource transmitted by the DeNB.

Research on mobile relay in 3GPP REL-11 standard has started. It is also expected that the mobile relay node (M-RN) will be standardized in the 3GPP REL-12 standard. In order to provide effective mobility for the M-RN, The use of different operator frequencies or the requirement that mobile relays operate in operation or in-band and out-band by supporting Multi-RAT (radio access technology) , And in particular, it has been decided as a "study item" for the in-band operation. The deployment of M-RN assumed by 3GPP assumes that it will be operated on high-speed trains such as TGV, Shinkansen, etc., moving at a speed of 300 Km or more on a predetermined orbit. That is, mobility support is required among a plurality of DeNB cells already installed on a railway track for M-RN.

In a typical UE, in a RRC connected mode, a cell change on an intra FA (FA) is performed a hard handover of a best cell concept to minimize interference. The UE determines whether the reference symbol received power (RSRP) of the serving cell is lower than the " s-measure ", which is the measurement initiation threshold for a new cell, To perform a new cell identification.

In the new cell detection process, the UE first recognizes slot timing detection and PCI (Physical Cell ID) through a PSS (Primary Synchronization Signal) of a new target cell A radio frame timing detection, a cell ID, a downlink cyclic prefix length, and a duplex mode through a secondary synchronization signal (SSS) (RSRP) / reference signal received quality (RSRQ) measurement result for the CRS is reported to the serving cell after determining the precise symbol position of the target cell with respect to the CRS (Common Reference Signal) , A handover preparation to a new target cell is performed.

However, in the case of the in-band M-RN, as shown in FIG. 1, the subframes sf # 0 and sf # 5 for allocating PSS and SSS can not be set to DL BHSF. Mobility support is not easy. Therefore, mobility is being studied in the in-band operation of REL-12 mobile relay in 3GPP.

As shown in FIGS. 2 and 3, in the 3GPP (RRC-10) standard or higher, radio frame synchronization (RLC) is performed for a TDM Inter-Cell Interference Coordination (ICIC) and a Multimedia Broadcast and Multicast Service radio frame synchronization. More specifically, for the TDM ICIC between the inter-eNBs (inter eNBs) in the 3GPP REL-10 standard and above, an X2 load indication is provided for interference coordination between the eNBs controlling the same frequency neighbor cell via the X2 interface (MBMS) service between the eNBs through an X2 setup and an eNB configuration update procedure by exchanging an ABS (Almost Blank Subframe) by performing a Load Indication , And MBSFN (Multimedia Broadcast Multicast Service Single Frequency Network) configuration information. That is, REl-12 DeNBs capable of supporting REL-12 M-RN, especially DeNBs located near the trajectory of high-speed trains, must be wireless frame-synchronized.

FIG. 4 is a diagram illustrating mobility support for M-RN. FIG. 4 illustrates a case where an inband M-RN (inband M-RN) is developed on a high-speed train.

In Fig. 4, DeNB (DeNB1) sets six DL BHSFs having a period of 40ms for M-RN. This corresponds to the combination of "01000000" + " 00000010 "of the eight basic DL BHSF patterns shown in FIG. After the DL BHSF is set up, the relay node (RN) no longer attempts to acquire the PSS, SSS, MIB of the DeNB cell, constructs an independent RN cell at the same time, Handover to the RN cell and (re) selection (re) selection are supported by transmitting the PSS, SSS, and MIB. That is, the RN constitutes an independent cell, and a PSS, a subframe, and a subframe are allocated to subframes sf # 0 and sf # 5 of an access link to support cell camping and (re) selection of UEs under RN cells, SSS should always be assigned and transmitted. At the same time, the RN does not allow data allocation to avoid SI for the subframes sf # 0 and sf # 5 on the backhaul link. Therefore, after the RN cell is formed on the backhaul link, it is impossible to detect the PSS, SSS of the target cell in addition to the serving cell for new DeNB cell identification. For this reason, there must be a way to provide effective mobility for the in-band M-RN.

4, the M-RN detects the PSS and the SSS of the DeNB (DeNB2) in order to measure the CRS (Cell Specific Reference Signal) of the DeNB (DeNB2) It is necessary to recognize the downlink cyclic prefix length, recognize the accurate timing position of the CRS of the DeNB (DeNB2) cell, measure RSRP (Reference Symbol Received Power), and report the measured RSRP to the DeNB (DeNB1) . To this end, the M-RN should be capable of receiving subframes sf # 0 and sf # 5, if necessary, under the serving cell of the DeNB (DeNB1) like a typical user equipment (UE). However, in the in-band scheme, since subframes sf # 0 and sf # 5 of the access link are always assigned PSS and SSS for cell camping and reselection of UEs under RN, subframes sf # 0 and sf # 5 can not be set to DL BHSF to avoid SI. That is, new DeNB cell identification on the backhaul link becomes impossible through PSS and SSS detection of a new target DeNB cell for mobility at that time.

In order to provide effective mobility to the in-band M-RN, data is allocated to the subframes sf # 0 and sf # 5 when introduced into the inter-DeNB handover region without service interruption to the UEs in the RN cell It is necessary to enable handover between the source DeNB (source DeNB) and the inter DeNB (inter DeNB). Therefore, it is possible to receive the subframes sf # 0 and sf # 5 on the backhaul link during in-service of the RN cell and to determine the reception timing for the subframes sf # 0 and sf # 5 It is important.

The REL-10 RN receives a DeNB cell list from the relay node operation management server at startup, selects the best cell from the received DeNB cell list and performs RRC connection to the DeNB cell, Instructs DeNB that it is an RN during the connection procedure.

In the case of the M-RN, as shown in Fig. 4, the movement direction due to the immediacy of the DeNB cell and the high-speed train which can move within the predetermined trajectory is not changed. That is, when the initial camping DeNB cell is determined upon power-on of the M-RN, the target DeNB cell to be moved thereafter can be predicted. The downlink timing offset information for radio frame synchronization between DeNBs (i.e., the downlink subframe offset, i.e., the downlink subframe offset) is calculated using the DeNB X2 setup procedure that is already located on the trajectory of the high- subframe offset information) of neighboring DeNBs and allocates an appropriate DL BHSF using the downlink sub-frame offset information of the target DeNB to be moved next time when it is served by the corresponding DeNB, so that the M- When the downlink data is not received in the DL BHSF set and serviced from the source DeNB corresponding to the subframes sf # 0 and sf # 5 of the target DeNB cell to be moved next, PSS and SSS of the target DeNB cell to be moved next are detected And obtains downlink time synchronization with the target DeNB cell. The M-RN then determines the downlink cyclic prefix length and attempts to evaluate the CRS of the target DeNB cell to notify the source DeNB of the measurement report. Thereafter, handover between the inter DeNBs is performed by performing a handover procedure between the inter-eNBs of a general UE. As a result, the downlink subframe numbering for the serving UEs under the M-RN cell is changed, and the physical uplink control channel (PUCCH) setting and the discontinuous reception (DRX) setting A change is required. In this case, the change can be reflected using the RRC Connection Reconfiguration message only for UEs serviced by the M-RN, and no procedure is required for the RRC_IDLE UE.

5 shows a state in which downlink timing is maintained between a DeNB cell "Y" and a DeNB cell "Z" by applying a downlink subframe offset set by an operator at DeNB power on, Quot; Y "to the DeNB cell" Z ". That is, it is recognized that the next target cell of DeNB cell "X" is DeNB cell "Y" and the subframe offset between DeNB cell "X" and DeNB cell "Y" is " It is recognized that the target cell is the DeNB cell "Z" and the subframe offset from the DeNB cell "Z" is "3". Therefore, when setting the DL BHSF, the DeNB corresponding to the DeNB cell "Y " is handed over from the DeNB cell" X "to the DeNB cell" The DL BHSF pattern is determined considering the information. That is, it can be seen that sf # 3 and sf # 8 of the first SFN of the DL BHSF of DeNB cell "Y" correspond to sf # 0 and sf # 5 of DeNB cell "Z" When DL BHSF including sf # 3 and sf # 8 of SFN is set, effective handover is possible when moving to DeNB cell "Z".

To this end, the subframe offset for each DeNB cell located on the high-speed train trajectory determined by the operator in the "X2 setup request" message and the "eNB configuration update" message of REL-12 X2- An addition to the IE (Information Element) to be included is required.

6 shows an example of adding a new IE to a message of at least one of the "X2 setup request" message and the "eNB configuration update" message of the REL-12 X2AP. Since all the eNBs do not need to support the relay node after the REL-10 standard defined in 3GPP, the relay node operation management server transmits the DeNB cell list at RN startup. That is, the IE is an optional IE because it is applied only to the eNB capable of supporting the RN, and the value range corresponds to the DL BHSF pattern period.

Thus, all of the 256 DL BHSFs may be used when determining the DL BHSF of the M-RN according to the active number of macro-UEs in which each of the DeNB's dynamically changes with the M-RN and the fixed RN.

Although the present invention has been described in connection with certain embodiments thereof, it should be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention as would be understood by one of ordinary skill in the art to which this invention belongs. something to do. It is also contemplated that such variations and modifications are within the scope of the claims appended hereto.

RN: relay node DeNB: donor base station
PCI: physical cell identifier
RN OAM: realy node operation and managment

Claims (12)

A target base station cell identification system,
A downlink backhaul subframe for avoiding self-interference (SI) with the subframe of the uplink based on preset downlink subframe offset information for radio frame synchronization A plurality of donor base stations operating;
A relay node operation management server operable to transmit cell list information corresponding to the plurality of donor base stations; And
Band basis and performs cell camping of cells of a first donor base station based on the cell list information and performs cell camping of cells of the first donor base station cell based on the downlink backhaul subframe provided from the first donor base station, A mobile relay node operative to identify a cell of a second donor base station for handover from a second donor base station
The target base station cell identification system comprising: The method of claim 1, wherein the first donor base station corresponds to a subframe for allocating a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) in an uplink subframe corresponding to the downlink subframe offset information Frame as a subframe to which the downlink backhaul subframe belongs. 3. The method of claim 2, wherein the first donor base station is configured to recognize the downlink sub-frame offset information between the first donor base station and the second donor base station using an X2 setup procedure, And to set the downlink backhaul subframe based on link subframe offset information. 4. The method of claim 3, wherein the first donor base station uses the message including an information element (IE) indicating the downlink subframe offset information with the second donor base station supporting the mobile relay node, X2 set-up procedure. 5. The target base station cell identification system of claim 4, wherein the message comprises at least one of an X2 setup request message and an eNB configuration update message. 6. The mobile relay node according to any one of claims 1 to 5,
Detecting a PSS and an SSS of the second donor base station based on a subframe corresponding to the downlink subframe offset information in the downlink backhaul subframe to obtain downlink time synchronization with a cell of the second donor base station,
To determine a downlink cyclic prefix length to attempt to evaluate a CSR (common reference signal) of a cell of the second donor base station, and to report a measurement report to the first donor base station. A method for identifying a target base station cell,
a) performing cell camping of cells of a first donor base station based on cell list information of a plurality of donor base stations located on predetermined trajectories on which a mobile body moves; And
b) from a cell of the first donor base station using a downlink backhaul subframe set to avoid SI and subframes of the uplink based on downlink subframe offset information for radio frame synchronization between adjacent donor base stations Identifying a cell of a second donor base station for handover
Wherein the target base station cell identification method comprises: The method of claim 7, wherein the downlink backhaul subframe is configured to include a subframe corresponding to the downlink subframe offset information as a subframe corresponding to a subframe for allocating the uplink PSS and the SSS. A method for identifying a target base station cell. 9. The method of claim 8, wherein the downlink backhaul subframe is configured based on the downlink subframe offset information between the first donor base station and a neighboring second donor base station using an X2 setup procedure. Way 10. The method of claim 9, wherein the X2 setup procedure is performed using a message including an IE indicating the downlink subframe offset information with the second donor base station supporting a mobile relay node operating in an in-band scheme Gt; a < / RTI > target base station cell. 11. The method of claim 10, wherein the message comprises at least one of an X2 setup request message and an eNB configuration update message. 12. A method according to any one of claims 7 to 11, wherein step b)
Detecting a PSS and an SSS of the second donor base station based on a subframe corresponding to the downlink subframe offset information in the downlink backhaul subframe to obtain downlink time synchronization with a cell of the second donor base station ; And
Determining a downlink cyclic prefix length and attempting to evaluate the CSR of the cell of the second donor base station and reporting a measurement report to the first donor base station
Wherein the target base station cell identification method comprises:

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