Abstract:
A method and an apparatus are provided in a first radio access technology (RAT). Mobility history information is generated including information on a time duration while in a second RAT. It is identified whether the terminal is in a Radio Resource Control (RRC) connected mode. The mobility history information is transmitted to a base station if the terminal is in the RRC connected mode.

Description:
PRIORITY 
     This application is a Continuation Application of U.S. application Ser. No. 12/769,126, filed in the U.S. Patent and Trademark Office on Apr. 28, 2010, which claims priority to an application filed with the Korean Intellectual Property Office on Apr. 28, 2009 and assigned Serial No. 10-2009-0037205, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a wireless communication network, and more particularly, to a method and an apparatus for managing User Equipment (UE) history information in order to improve performance of the wireless communication network. 
     2. Description of the Related Art 
     Generally, a Universal Mobile Telecommunications System (UMTS) is a third generation (3G) mobile communication system that uses Wideband Code Division Multiple Access (WCDMA) based on Global System for Mobile communications (GSM) and General Packet Radio Services (GPRS). A third Generation Partnership Project (3GPP) for standardization of the UMTS has suggested an Evolved Packet System (EPS) of the UMTS similar to the Long Term Evolution (LTE) system. In this case, the LTE system is a technology for implementing high-speed packet based communication. 
     In the EPS, while a source base station is downloading source data, a handover of a User Equipment (UE) can occur from the source base station to a target base station. At this time, the source base station forwards the source data to the target base station. Further, the target base station downloads the source data and next followed target data. In this case, the source base station records UE history information as a UE Context. Upon handover, the source base station transfers the UE history information to the target base station. 
     The UE history information may include cell ID, cell type (large, small, etc.), a time served from a cell, and information on a plurality of cells with information of a recent serving cell. The UE history information is used to prevent a ping-pong handover of a UE from a target cell (a continuous handover of the UE between two base stations within a short time) and for a radio resource allocation algorithm to the UE after estimation of a moving speed of the UE. However, the UE does not process the UE history information even though the serving base station creates it. When the UE firstly accesses the serving base station, because the UE history information is not created, the serving base station cannot use the UE history information. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above problems, and provides a method for managing UE history information in a wireless communication network that collects and provides its history information by an UE operating in an idle mode to the wireless communication network, thereby providing an efficient data transmission environment to the UE and providing valid information on an operation of a wireless communication system to the wireless communication network. 
     In accordance with an aspect of the present invention, a method is provided by a terminal in a first radio access technology (RAT). Mobility history information is generated including information on a time duration while in a second RAT. It is identified whether the terminal is in a Radio Resource Control (RRC) connected mode. The mobility history information is transmitted to a base station if the terminal is in the RRC connected mode. 
     In accordance with another aspect of the present invention, a terminal is provided in a first RAT. The terminal includes a communication unit for receiving and transmitting a signal with a base station. The terminal also includes a controller for generating mobility history information including information on a time duration while in a second RAT, identifying whether the terminal is in an RRC connected mode, and transmitting the mobility history information to a base station if the terminal is in the RRC connected mode. 
     In a method for managing UE history information in a wireless communication network accordance with the present invention, an UE transmits its UE history information to a serving base station, so that the serving base station can provide an efficient data transmission environment to the UE based on the UE history information. Further, the UE transmits its UE history information to an O&amp;M (Operating and Management) server or a core network entity of a wireless communication network, so that a network operator can use the UE history information for managing the wireless communication network. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, features and advantages of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram illustrating a configuration of a wireless communication network according to an embodiment of the present invention; 
         FIG. 2  is a sequence diagram illustrating a method for transmitting UE history information from a source base station to a target base station at the time of a handover between macro base stations according to an exemplary embodiment of the present invention; 
         FIG. 3  is a diagram illustrating history information recorded by a UE operating in an idle mode according to an embodiment of the present invention; 
         FIG. 4  is a diagram illustrating a procedure of recording UE history information by a UE operating in an idle mode according to an embodiment of the present invention; 
         FIG. 5  is a sequence diagram illustrating a procedure of transmitting idle mode UE history information to a base station by a UE in an idle mode according to an embodiment of the present invention; 
         FIG. 6  is a flow chart illustrating an operation of a UE according to an embodiment of the present invention; and 
         FIG. 7  is a block diagram illustrating an internal configuration of a UE according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention are described with reference to the accompanying drawings in detail. The same reference numbers are used throughout the drawings to refer to the same or like parts. Detailed descriptions of well-known functions and structures incorporated herein may be omitted to avoid obscuring the subject matter of the present invention. 
     First, a configuration of a wireless communication network is described. The wireless communication network according to an embodiment of the present invention is configured based on a cellular system. 
       FIG. 1  is a diagram illustrating a configuration of a wireless communication network according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the wireless communication network according to an embodiment of the present invention includes a User Equipment (UE)  101 , an Evolved UMTS Radio Access Network (E-UTRAN)  102 , a Mobility Management Entity (MME)  103 , a Serving GateWay (SGW)  104 , a Packet data network GateWay (PGW)  105 , a Packet Data Network  106 , and an Operator Network  107 . The user equipment  101  may be fixed or mobile. 
     The E-UTRAN  102  accesses the UE  101  through a wireless channel. The E-UTRAN  102  is composed of a plurality of cells. The E-UTRAN  102  includes a plurality of evolved base stations, or Node Bs (eNBs) for controlling respective cells. The evolved base stations eNBs may be connected to each other through an X2 interface. The evolved base stations (eNBs) execute a radio bearer control function, a radio admission control function, a connection mobility control function, and a Radio Resource Management (RRM) function such as dynamic resource allocation to the UE  101 . Further, the evolved base stations eNBs execute an Internet Protocol (IP) header compression and data encryption function, a data routing function, a scheduling and transmitting function of a paging message, a scheduling and transmitting function of broadcast information, a measurement function for mobility and scheduling, and a measurement report set function. Namely, the evolved base stations eNBs receive downloading of data and transmits the downloaded data to the UE  101 . 
     The E-UTRAN  102  includes a source base station and a target base station. The source base station indicates a base station currently being accessed by the UE  101 . The target base station indicates a base station that the UE  101  wants to access through hand-over. Namely, upon a handover from the source base station to the target base station, the UE  101  terminates access to the source base station, and initiates access to the target base station. In other words, when the UE  101  accesses the source base station, the source base station downloads source data. Upon the hand-over from the source base station to the target base station, the source base station forwards source data to the target base station. Further, the target base station downloads target data followed by the source data. At this time, the source base station transmits UE history information recorded as an UE Context to the target base station at the time of the handover. 
     The MME  103  accesses the E-UTRAN  102  by a wired channel. In this case, the MME  103  is connected to the E-UTRAN  102  through an SI interface. The MME  103  executes a paging message distribution function to the evolved base station, a ciphering and integrity protection function of Non-Access Stratum (NAS) signaling, an idle state mobility control function, and a bearer control function. 
     The SGW  104  accesses the E-UTRAN  102  and the MME  103  by a wired channel. In this case, the SGW  104  is connected to the E-UTRAN  102  through an SI interface. The SGW  104  can be provided with plurality of SGWs. Namely, the SGW  104  accesses at least one evolved base station. Further, the SGW  104  executes a mobility control function of the UE  101  and the like. 
     The PGW  105  accesses the SGW  104  by a wired channel. The PGW  105  further accesses an IP network. The PGW  105  executes an IP address allocation function and a data filtering function for the UE  101 . That is, the PGW  105  transmits data provided from an IP network  106  to the UE  101  through the SGW  104  and the E-UTRAN  102 . 
       FIG. 2  is a sequence diagram illustrating a method for transmitting UE history information from a source base station to a target base station at the time of a handover between macro base stations according to an embodiment of the present invention. 
     Referring to  FIG. 2 , a User Equipment (UE)  201  detects a signal of a target base station (eNB)  203 , and transmits a measurement report to a serving base station (eNB)  202  in step  205 . Next, the serving base station  202  analyzes the received measurement report, checks which base station is a target base station of the UE  201 , and decides a handover of the UE based on a Tracking Area ID (TAI) and a used frequency band of the target base station  203  in step  206 . The serving base station  202  transfers a handover request message and UE history information to the target base station  202  in step  207 . The target base station  203  transmits a response indicating a handover request ACK to the serving base station  202  in step  208 . Then, the serving base station  202  instructs the UE  201  to perform a handover to the target base station  203  in step  209 . 
     Subsequently, the UE  201  performs a handover to the target base station  203  in step  210 . The target base station  203  informs in step  211  an MME  204  that the handover of the UE  201  is performed. The MME  204  transmits a response signal (e.g. Path switch ACK) to the target base station  203  in step  212 , and instructs the service base station  202  to erase all UE information in step  213 . The serving base station  202  informs the success of reception of the UE information and the resources used by the UE  201  to the MME  204  in step  214 . 
     The UE history information in step  207  contains cell ID, cell type (large, small, etc.), a served time from a corresponding base station, and information on a plurality of base stations with recent information of a serving base station. The UE history information is used to prevent a ping-pong handover of a UE from a target cell, namely, a continuous handover of the UE between two base stations within a short time, and for a radio resource allocation algorithm to the UE after estimation of a moving speed of the UE. 
     The following is an explanation of a method for using history information of an UE operating in an idle mode according to an embodiment of the present invention. Herein, the idle mode is a state in which a Radio Resource Control (RRC) connection established between an UE and a base station is released. Meanwhile, an active mode means a state in which RRC connection between an UE and a base station is established. 
       FIG. 3  is a diagram illustrating history information recorded by a UE operating in an idle mode according to an embodiment of the present invention. 
     Referring to  FIG. 3 , when a recording event occurs in an idle mode, a UE directly records information about the occurred recording event in idle mode UE history information. Upon conversion to an active mode, namely, upon setting the RRC connection between the UE and a base station, the UE transmits the recorded UE history information to the connected base station. 
     In particular, as shown in  FIG. 3 , the UE operating in the idle mode manages the UE history information in a form of a table. The UE history information contains at least one of an occurrence event, an ID and related information thereof selected by the user equipment, Public Land Mobile Network (PLMN) information selected by the UE, a time influenced by each event, a time occupying a corresponding cell, and measuring information in the idle mode UE history information. Although not shown, besides the items listed, measurement information items with a cell signal strength may be included in the table of  FIG. 3 . Here, the cell signal strength may include a self-cell signal strength, a neighbor cell signal strength, or a signal strength of currently camped frequency or different band frequencies. As described above, it should be considered that respective items are listed in the table shown in  FIG. 3  by way of example only. The respective items can be removed as needed. In another case, different items can be included in history information recorded in a UE operating in an idle mode. 
       FIG. 4  is a diagram illustrating a procedure of recording UE history information by a UE operating in an idle mode according to an embodiment of the present invention. 
     Referring to  FIG. 4 , a UE  401  operating in an active mode converts to an idle mode in a first cell  404 , moves to cell  04   407  in an idle mode, and again operates in the active mode in a fourth cell  407 . 
     In detail, when an event  408  converting to an idle mode occurs in the first cell  404 , the UE  401  records information regarding the occurred event  408  in idle mode UE history information. More particularly, an event with a change of a serving cell occurs in the UE, and the UE records a time stayed in a previous serving cell, namely, the first cell  404 , and information about a second cell  405  being a current serving cell in the idle mode UE history information. 
     Next, when the UE enters into an impossible service zone (i.e. an area where no service is available) and a service impossibility event  410  occurs, the UE records a time stayed in a second cell  405  being a previous serving cell and current service impossibility information in the idle mode UE history information. When the UE enters into a third cell  406 , it executes an event selecting a PLMN and a cell, and records the occurrence time of the service impossibility event and information about a current PLMN and service cell in the idle mode UE history information. 
     When the UE continuously moves and an event in which a serving cell changes from the third cell  460  to the fourth cell  407  occurs, the UE records a time stayed in the third cell  360  being a previous serving cell and information about the fourth cell  407  being a current serving cell in the idle mode UE history information. 
     When the UE accesses the fourth cell  407  and a conversion event from an idle mode to an active mode occurs, the UE records a time of the fourth cell  407  being a current serving cell operating in the idle mode in the idle mode UE history information. The idle mode UE history information recorded according to an embodiment of  FIG. 4  is as shown in  FIG. 3 . 
       FIG. 5  is a sequence diagram illustrating a procedure of transmitting idle mode UE history information to a base station by a UE in an idle mode according to an embodiment of the present invention. 
     Referring to  FIG. 5 , after a connection between a UE  501  in an idle mode and an RRC is established, i.e. when the UE  501  is converted to an active mode, in step  504 , the UE  501  transmits idle mode UE history information to a base station  503  in step  506 . In this case, step  506  can be performed by a request from the base station  502  in step  505  or independently while omitting step  505 . 
     Further, step  506  can be performed after step  504  or as a part of step  504 . The base station  502  which received the idle mode UE history information may share the idle mode UE history information or information related thereto with another core network entity, i.e, a core network entity such an O &amp; M server or an MME in step  507 . Meanwhile, the base station  503  may share the idle mode UE history information or information related thereto with another base station neighboring therewith. Another base station or another core network entity may estimate a moving speed of a UE and then use the idle mode UE history information in a radio resource allocation algorithm, in acquisition of information about its neighbor cells, PCI selection algorithm, problem discovery at the time of an enterpriser&#39;s cell planning or setting a cell parameter, a coverage problem discovery of an enterpriser cellular network, and automatic setting of other networks. 
       FIG. 6  is a flow chart illustrating an operation of a UE according to an embodiment of the present invention. 
     Referring to  FIG. 6 , a UE determines if it is in an idle mode in step  601 . When the UE is in the idle mode, the UE executes Radio Frequency (RF) channel search in step  602 . The UE determines if an idle mode event to be recorded occurs in step  603 . When the idle mode event to be recorded occurs, the UE further records relation event information in the idle mode UE history information in step  604 . 
     When the UE is not in an idle mode at step  601 , the UE determines if it is attempting to access a base station in step  605 . When the UE is attempting to access a base station, the UE determines if it succeeds in accessing the base station to be converted to an active mode in step  606 . When the UE is converted to the active mode, the UE receives a request for the idle mode UE history information from the base station in step  607  and transmits the idle mode UE history information to the base station in step  608 . In this case, step  608  may be performed according to the request for the idle mode UE history information from the base station  520  in step  607  or be performed independently while omitting step  607 . 
       FIG. 7  is a block diagram illustrating an internal configuration of a UE according to an embodiment of the present invention. Referring to  FIG. 7 , the UE according to an embodiment of the present invention includes an RF communication unit  710 , a storage unit  720 , and a controller  730 . The storage unit  720  may include a UE history information storing area  720 A. The controller  730  may include a UE history information generator  730 A and a UE history information transmitting controller  730 B. 
     The RF communication unit  710  performs transmitting and receiving functions of corresponding data for a wireless communication of the UE. The RF communication unit  710  may be composed of an RF transmitter that up-converts a frequency of a signal to be transmitted and amplifies the signal, and an RF receiver that low-noise amplifies a received signal and down-converts a frequency of the amplified signal. The RF communication unit  710  may receive data through a wireless channel, output the received data to the controller  730 , and transmit data output from the controller  730  through the wireless channel. In particular, the RF communication unit  710  according to an embodiment of the present invention may transmit the idle mode UE history information generated from the UE in an idle mode to a base station. 
     The storage unit  720  stores programs and data necessary for the overall operation of the UE according to an embodiment of the present invention, and may include a UE history information storing area  720 A. The UE history information storing area  720 A stores idle mode UE history information generated in the UE in an idle mode. 
     The controller  730  controls signal transmission between respective blocks of another UE according to an embodiment of the present invention. In particular, the controller  730  controls a series of procedures for transmitting the idle mode UE history information according to an embodiment of the present invention. To do this, the controller  730  may include a UE history information generator  730 A and the UE history information transmitting controller  730 B. 
     The UE history information generator  730 A determines if a UE is in an idle mode. When the UE is in the idle mode, the UE history information generator  730 A performs RF channel search to determine if a recording event to be recorded in UE history information occurs. Referring to  FIG. 4 , the recording event may include at least one of an idle mode conversion event, a cell change event, an impossible service event, a cell re-selection event, and a cell change event. 
     When the recording event occurs, the UE history information generator  730 A records relation information in the idle mode UE history information. As described above, the idle mode UE history information contains at least one of an occurrence event, an ID and related information thereof selected by the UE, Public Land Mobile Network (PLMN) information selected by the UE, a time influenced by each event, a time camped in a corresponding cell, a cell signal strength, and measuring information. The UE history information transmitting controller  730 B controls the generated idle mode UE history information to be stored in the UE history information storing area  720 B. 
     The UE history information transmitting controller  730 B determines if a UE operating in an idle mode succeeds accessing a base station to be converted into an active mode. When being converted to the active mode from the idle mode, the UE history information transmitting controller  730 B controls the idle mode UE history information to be transmitted to the base station. In this case, the idle mode UE history information can be transmitted simultaneously with the accessing of the base station or according to a request from the base station. 
     In the method for managing UE history information according to the present invention, a UE may transmit its UE history information to a serving base station, and the serving base station may provide an efficient data transmission environment to the UE base on the UE history information. 
     Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims.