Title of Invention: METHOD AND APPARATUS FOR SELF-CONFIGURATION AND SELF-OPTIMIZATION IN A WIRELESS COMMUNICATION SYSTEM Abstract: The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). An apparatus implements a method for self-configuration and self-optimization. A method for operating a base station (BS) in a wireless communication network comprises transmitting a message including information on coverage modification indicating whether the message is for pre-notification of cell re-configuration, to another BS, and receiving an acknowledgement message from the another BS. Detailed Description: CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY The present application is related to and claims the benefit under 35 U.S.C. §119(a) of a Chinese patent applications filed on Aug. 12, 2015 in the State Intellectual Property Office of the P.R.C and assigned Serial number 201510494452.4, and filed on and Aug. 14, 2015 in the State Intellectual Property Office of the P.R.C and assigned Serial number 201510501880.5, the entire disclosure of which is hereby incorporated by reference. TECHNICAL FIELD The present disclosure relates to mobile communication systems, and especially to a method, a system, and an apparatus for self-configuration and self-optimization. BACKGROUND To meet the demand for wireless data traffic having increased since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution (LTE) System’. The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like. In the 5G system, Hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed. The existing solutions still cannot effectively solve the problem of re-establishment failure during SAE system self-optimization, in the scenarios of cell splitting/merging and cell shaping. SUMMARY A method for self-configuration and self-optimization is provided according to embodiments of the present disclosure. The method may be able to solve the problems of re-establishment failure subsequently after a handover failure of a user equipment (UE) and mobility robustness optimization (MRO) during a self-optimization procedure of a system architecture evolution (SAE) system in scenarios of cell splitting/cell merging and cell shaping. A system for self-configuration and self-optimization is provided according to embodiments of the present disclosure. The system may be able to solve the problems of re-establishment failure subsequently after a handover failure of a UE and MRO during a self-optimization procedure of an SAE system in scenarios of cell splitting/cell merging and cell shaping. An apparatus for self-configuration and self-optimization is provided according to embodiments of the present disclosure. The apparatus may be able to solve the problems of re-establishment failure subsequently after a handover failure of a UE and MRO during a self-optimization procedure of an SAE system in scenarios of cell splitting/cell merging and cell shaping. To achieve the objects, technical schemes of the embodiments of the present disclosure are implemented as follows. A method for self-configuration and self-optimization, includes: notifying, by a base station (BS) which controls a coverage modification cell, information on coverage modification to a second BS before or after performing cell re-configuration. A system for self-configuration and self-optimization, includes: a BS which controls a coverage modification cell and a second BS, in which the BS which controls the coverage modification cell is to notify information on coverage modification to a second BS before or after cell re-configuration; and the second BS is to make multiple preparations for a handover, and/or save or update modification information of the coverage modification cell, and/or save or retrieve a MRO status of a modified cell according to the information on coverage modification. A BS for self-configuration and self-optimization, which controls a coverage modification cell, includes: a configuring module and an instructing module, in which the configuring module is to perform cell re-configuration; and the instructing module is to notify information on cell coverage modification to a second BS after performing the cell re-configuration. A second BS for self-configuration and self-optimization, includes a receiving module and a processing module, in which the receiving module is to receive information on coverage modification sent from a BS which controls a coverage modification cell; and the processing module is to make multiple preparations for a handover, and/or save or update modification information of a coverage modification cell, and/or save or retrieve a MRO status of a modified cell according to the received information on coverage modification. In the method, system, and apparatus provided according to the embodiments of the present disclosure, a BS which controls a coverage modification cell notifies information on coverage modification to a second BS. The second BS saves or updates modification information of a coverage modification cell, and/or saves or retrieves a MRO status of a related cell, and/or makes multiple preparations for a handover. In this way, the embodiments of the present disclosure enable the second BS to properly save, retrieve a MRO status of a coverage modified cell, to know the cells to be served as the multiple preparations for the handover in time to solve the problem of re-establishment failure; and release unnecessary information such as PCIs in time, so as to use radio resources and system resources to the most extent, better support MRO, and improve performance of the mobile communication system. Therefore, the embodiments of the present disclosure may be able to solve the problems of re-establishment failure subsequently after a handover failure of a UE and MRO during a self-optimization procedure of an SAE system in scenarios of cell splitting/cell merging and cell shaping. In one embodiment, a method for operating a BS in a wireless communication network comprises transmitting a message including information on coverage modification indicating whether the message is for pre-notification of cell re-configuration, to another BS, and receiving an acknowledgement message from the another BS. In another embodiment, a BS in a wireless communication network comprises a a controller configured to perform cell re-configuration, and a communication unit configured to transmit a message including information on coverage modification indicating whether the message is for pre-notification of the cell re-configuration, to another BS, and receive an acknowledgement message from the another BS. In still another embodiment, a BS in a wireless communication network comprises a communication unit configured to receive a message including information on coverage modification indicating whether the message is for pre-notification of cell re-configuration, from another BS, and a controller configured to operate for avoiding connection or re-establishment failure during the cell re-configuration based on the information on coverage modification. Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: FIG. 1 illustrates a schematic diagram of a structure of a system architecture evolution (SAE) system; FIG. 2 illustrates a schematic diagram of a basic principle of performing self-optimization for an SAE system; FIG. 3 illustrates a first self-configuration and self-optimization method provided according to embodiments of the present disclosure; FIG. 4 illustrates a second self-configuration and self-optimization method provided according to embodiments of the present disclosure; FIG. 5 illustrates a first self-optimization method which supports a cell coverage modification scenario provided according to embodiments of the present disclosure; FIG. 6 illustrates a second self-optimization method which supports a cell coverage modification scenario provided according to embodiments of the present disclosure; FIG. 7 illustrates a third self-optimization method which supports a cell coverage modification scenario provided according to embodiments of the present disclosure; FIG. 8 illustrates a fourth self-optimization method which supports a cell coverage modification scenario provided according to embodiments of the present disclosure; FIG. 9 illustrates a first embodiment of the self-optimization method which supports a cell coverage modification scenario provided according to embodiments of the present disclosure; FIG. 10 illustrates a second embodiment of the self-optimization method which supports a cell coverage modification scenario provided according to embodiments of the present disclosure; FIG. 11 illustrates a schematic diagram of a structure of a self-configuration and self-optimization system provided according to embodiments of the present disclosure; and FIG. 12 illustrates block diagram of a base station (BS) in a wireless communication system according to an embodiment of the present disclosure. DETAILED DESCRIPTION FIGS. 1 through 12, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication system. For better understanding of the objects, technical solutions, and advantages of the present disclosure, the present disclosure will be described more fully hereinafter with reference to the accompanying drawings and embodiments. With the development of communication techniques, mobile communication systems have evolved to system architecture evolution (SAE) systems. FIG. 1 illustrates a schematic diagram of a structure of an SAE system. As shown in FIG. 1, the system includes an evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN) 101 and a core network, which at least includes a mobility management entity (MME) 105 and a user plane entity (serving-gateway (S-GW)) 106. The E-UTRAN 101 is configured to connect a user equipment (UE) to the core network. The E-UTRAN 101 may further include at least one macro enhanced NodeB (eNB) 102 and home enhanced NodeB (HeNB) 103, and may optionally include a home enhanced NodeB gateway (HeNB GW) 104. The MME 105 and the S-GW 106 may be integrated into a single module, or may be implemented separately. The eNBs 102 are connected with each other through X2 interfaces, and are connected to the MME 105 and the S-GW 106 through S1 interfaces. The HeNBs 103 are directly connected to the MME 105 and the S-GW 106 through S1 interfaces respectively, or are connected with the optional HeNB GW 104 through S1 interfaces, and then the HeNB GW 104 is connected to the MME 105 and the S-GW 106 through S1 interfaces respectively. At initial establishment of the SAE system, or during the operation of the SAE system, a great amount of manpower and material resources is the cost to configure and optimize parameters of the SAE system, especially settings of radio parameters, so as to provide good coverage and capacity, mobility robustness, mobility load balance, UE accessing rate, etc. To save the manpower and material resource costs for the configuration during the operation of the SAE system, a method for self-optimization of the SAE system is one proposed solution. During a self-optimization process, settings of an eNB or HeNB are optimized based on a current status of the SAE system. Bothe eNB and HeNB are referred to as “eNB” hereinafter to illustrate the method for self-optimization of the SAE system. FIG. 2 illustrates a schematic diagram of a basic principle for self-optimization of an SAE system. As shown in FIG. 2, upon the powering on of an eNB, or upon access to the SAE system by the eNB (block 217), a self-configuration process which involves basic configuration and initial radio parameter configuration of the eNB may be carried out. In block 219, the basic configuration of the eNB includes configuration of an internet protocol (IP) address for the eNB, and detection of operations, administration and maintenance (OA&M) (block 201); authentication between the eNB and the core network (block 203); in case of the eNB being a HeNB, detection of a HeNB GW to which the eNB belongs (block 205); and download of software and operation parameters of the eNB to perform self-configuration (block 207). In block 221, initial radio parameter configuration may be carried out according to experience or simulation. Since performance of respective eNBs in the SAE system may be affected by environments where the respective eNBs are located, the eNBs need to perform initial radio parameter configuration (block 221) according to the environments where the eNBs are located, and especially perform an initial configuration of neighboring cell list (block 209) and an initial configuration of load balance (block 211). After the self-configuration procedure, since a lot of parameters configured for the eNBs may not be optimal, it is necessary to optimize or adjust configurations of the eNBs (block 223), so that the SAE has better performance, which is also referred to as self-optimization of the mobile communication system. A backstage OA&M may control an eNB to optimize or adjust configurations of the eNB. There may be a standard interface between the OA&M and the eNB, and the OA&M may send parameters to be optimized through the interface to the eNB. The eNB may be an eNB or a HeNB. Then, the eNB may optimize parameters configured for it according to the parameters to be optimized. Of course, the process may be carried out by the eNB itself. That is, the eNB detects and obtains performance to be optimized, and then optimizes and adjusts parameters corresponding to it. Optimization or adjustment of the configurations of eNB may include: neighboring cell list self-optimization (block 213), coverage and capacity self-optimization, mobility robustness self-optimization, load balance self-optimization (block 215), and random access channel (RACH) parameter self-optimization. In a scenario where cell coverage is modified, three adaptive antenna system (AAS) scenarios: cell shaping, cell splitting/merging, and cell beamforming need to be considered for self-configuration and self-optimization. In the scenarios of cell splitting/merging and of cell shaping, a problem of re-establishment failure and a problem of mobility robustness optimization (MRO) may be caused subsequently after a handover failure of a UE. There is not yet a comprehensive solution to solve the problem of re-establishment failure and the problem of MRO. For example, if a cell C is split into a cell D and a cell E, how will a base station (BS) that controls the cell C notify the status of the cell C to a neighboring BS? If the cell C is put in a deleted-cell list, then the neighboring BS may delete information related to the cell C. In this case, the neighboring BS will not be able to save parameters related to mobility of the cell C, and next time when the cell C is changed to be active, the neighboring BS cannot retrieve the parameters related to self-optimization (mobility robustness optimization) of the cell C. However, if the cell C is not put in deleted-serving cell information, even if the cell C is not working, some information, such as a physical-layer cell identity (PCI) of the cell C, cannot be released in time, and thus, PCI conflicts may occur, which is disadvantageous for system planning. Again, the existing solutions still cannot effectively solve the problem of re-establishment failure during SAE system self-optimization, in the scenarios of cell splitting/merging and cell shaping. As described above, a reason that causes the problems of re-establishment failure subsequently after a handover failure of a user equipment (UE) and mobility robustness optimization (MRO), during a self-optimization procedure of a system architecture evolution (SAE) system in the scenarios of cell splitting/cell merging and cell shaping is that a second base station (BS) may not be able to know cells to be served as multiple preparations for the handover in time, and may not be able to know modification information of the coverage modification cell in a BS which controls a coverage modification cell. In view of the foregoing, in the embodiments of the present disclosure, the BS that controls the coverage modification cell notifies information on coverage modification to the second BS, so that the second BS saves or updates information of the coverage modification cell, and/or saves or retrieves the MRO status of a related cell, and/or makes multiple preparations for the handover. In this way, the embodiments of the present disclosure enable the second BS to properly save, and retrieve the MRO status of the coverage modification cell, to know the cells to be served as the multiple preparations for the handover in time to solve the problem of re-establishment failure, and release unnecessary information such as physical cell identities (PCIs), so as to use radio resources and system resources to the most extent, better support MRO, and improve performance of the mobile communication system. FIG. 3 illustrates a first self-configuration and self-optimization method provided according to embodiments of the present disclosure. The detailed process of the method may be as follows. Step 301, a BS 1 notifies a BS 2 of information on coverage modification. The BS 1 is a BS that controls a coverage modification cell. The BS controls a cell with modified coverage. The BS 2 may be a BS that has an X2 interface with the BS 1, or a neighboring BS of the BS 1. In step 301, the information on coverage modification may include one or more kinds of following information: a cell identity of the cell with modified coverage, i.e., an evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN) cell global identifier (ECGI); a cell coverage status of the cell with modified coverage; cell replacing information related to the cell with modified coverage; a cell deployment status indication of the cell with modified coverage, i.e., indicating whether the information on coverage modification is a notification before coverage modification or a notification after coverage modification. That is, the information on coverage modification may include a cell identity of the coverage modification cell, i.e., an E-UTRAN cell global identifier (ECGI); a cell coverage status of the coverage modification cell; a list of associated cells of the coverage modification cell; a coverage deployment status indication of the coverage modification cell, i.e., indicating whether the information on coverage modification is a notification before coverage modification or a notification after coverage modification. The information on coverage modification comprises cell replacing information related to the cell with modified coverage, when the information on coverage modification includes the cell deployment status indicator. The cell deployment status indicator in the information on coverage modification indicates that the cell coverage status is planned to be used at the next re-configuration. In step 301, the coverage deployment status indication may be set as potential deployment to indicate that the information on coverage modification is a notification before coverage modification. That is, the information on coverage modification indicates pre-notification of cell re-configuration. In case of absence of the coverage deployment status indication, it means that the information on coverage modification is a notification after coverage modification. That is, the information on coverage modification indicates post-notification of the cell re-configuration. The message including the information on coverage modification is for pre-notification of the cell re-configuration, when the information on coverage modification includes a cell deployment status indicator and the cell deployment status indicator indicates pre-change-notification or potential deployment. The information on coverage modification comprises cell replacing information related to the cell with modified coverage, when the information on coverage modification includes the cell deployment status indicator. The cell deployment status indicator in the information on coverage modification indicates that the cell coverage status is planned to be used at next re-configuration. In the method of the present disclosure, the BS 1 may not send information elements of the coverage deployment status indication to the BS 2, but may let the BS 2 know whether the information on coverage modification is a notification before coverage modification or a notification after coverage modification by implicit approaches. There may be two implicit approaches to let the BS 2 know whether the information on coverage modification is a notification before coverage modification or a notification after coverage modification as follows. That is, there may be two implicit approaches to let the BS 2 know whether the information on coverage modification indicates pre-notification of cell re-configuration or post-notification of the cell re-configuration. Approach 1: corresponding to notification before coverage modification, the information on coverage modification sent from the BS 1 to the BS 2 contains information elements of the list of associated cells of the coverage modification cell. While corresponding to notification after coverage modification, the BS 1 may not contain the information elements of the list of associated cells of the coverage modification cell in the information on coverage modification, because the BS 2 had received and saved information on the associated cells after it received a notification before coverage modification. Approach 2: the BS 2 may know whether the information on coverage modification received from the BS 1 is a notification before cell re-configuration, or a notification after cell re-configuration based on the cell identity and the cell coverage status of the coverage modification cell. Corresponding to notification before coverage modification, the cell coverage status of the coverage modification cell is the same as an existing status. Being the same as an existing status means that the cell coverage status of the coverage modification cell is the same as a status of a corresponding cell saved by the BS 2 (e.g., both are either inactive, or active), or the cell coverage status of the coverage modification cell is inactive but there is no information on the corresponding cell at the BS 2. Corresponding to notification after coverage modification, the cell coverage status of the coverage modification cell received by the BS 2 is different from a status of the coverage modification cell saved by the BS 2. In the method of the present disclosure, there may be only a notification before coverage modification, or only a notification after coverage modification, or both a notification before coverage modification and a notification after coverage modification. When there is only a notification after coverage modification, the step 301 is executed after step 302. When there are both a notification before coverage modification and a notification after coverage modification, the notification before coverage modification is notified in the step 301, and the notification after coverage modification is notified after step 302. In step 301, the cell coverage status of the coverage modification cell indicates an inactive status or an active status of the coverage modification cell. Corresponding to notification before coverage modification, the BS 1 put information of a cell, which is currently in the inactive status, in information of serving cells to be modified, or in information of serving cells to be added. That is, the BS put information of a cell with modified coverage is included in information of served cells to be modified or in information of served cells to be added. If it is the first time to make a cell re-configuration preparation to generate the cell in the inactive status, then the information of the cell will be contained in the information of the serving cells to add. If the cell in the inactive status has once been activated, then the information of the cell will be contained in the information of the serving cell to be modified. The BS 1 may allocate a new PCI for the cell, and contain the new PCI in the information of the serving cells to be modified. After the BS 2 receives the information on coverage modification, it may save information of a modified serving cell or information of an added serving cell. Corresponding to notification after coverage modification, the BS 1 may release a PCI of the cell in the inactive status. The BS 1 saves an ECGI of the cell in the inactive status. After the BS 2 receives the notification after coverage modification, it will know that the PCI of the corresponding cell in the inactive status has been released. In step 301, when the information on coverage modification contains a notification before coverage modification, then the BS 2 may make multiple preparations for a handover, and the BS 2 saves information of a modified serving cell and/or modification information of a coverage modification cell; when the information on coverage modification contains a notification after coverage modification, then the BS 2 may retrieve a MRO status of a cell in the active status, and save a MRO status of a cell in the inactive status. The BS 2 may operate for avoiding connection or re-establishment failure during the cell re-configuration based on the information on coverage modification received from the BS 1. Corresponding to a coverage modification cell whose cell coverage status is inactive, the BS may not initiate a handover to the coverage modification cell. Step 302, the BS 1 performs cell re-configuration. The cell re-configuration includes cell splitting, cell merging, and cell shaping. FIG. 4 illustrates a second self-configuration and self-optimization method provided according to embodiments of the present disclosure. The detailed process of the method may be as follows. Step 401, the BS 2 receives information on coverage modification sent from the BS 1. In step 401, information on coverage modification may include one or more kinds of following information: a cell identity of a cell with modified coverage, i.e., an ECGI; a cell coverage status of the cell with modified coverage; cell replacing information related to the cell with modified coverage; a coverage deployment status indication of the cell with modified coverage, i.e., indicating whether the information on coverage modification is a pre-notification of cell re-configuration or post-notification. That is, the information on coverage modification may include a cell identity of a coverage modification cell, i.e., an ECGI; a cell coverage status of the coverage modification cell; a list of associated cells of the coverage modification cell; a coverage deployment status indication of the coverage modification cell, i.e., indicating whether the information on coverage modification is a notification before coverage modification or a notification after coverage modification. To be consistent with the foregoing description of step 301, if the coverage deployment status indication is set to be potential deployment, then it shows that the information on coverage modification is a notification before coverage modification. That is, if the cell deployment status indicator indicates pre-change-notification or potential deployment, then a message regarding the information on coverage modification is pre-notification of the cell re-configuration. The message including the information on coverage modification is for pre-notification of the cell re-configuration, when the information on coverage modification includes a cell deployment status indicator and the cell deployment status indicator indicates pre-change-notification or potential deployment. If the coverage deployment status indication is not present, then it shows that the information on coverage modification is a notification after coverage modification. Or the BS 1 may let the BS 2 know whether the information on coverage modification is a notification before coverage modification or a notification after coverage modification by an implicit approach. The information on coverage modification comprises cell replacing information related to the cell with modified coverage, when the information on coverage modification includes the cell deployment status indicator. The cell deployment status indicator in the information on coverage modification indicates that the cell coverage status is planned to be used at next re-configuration. In step 401, the cell coverage status of the coverage modification cell indicates an inactive status or an active status of the coverage modification cell. Step 402, based on the received information on coverage modification, the BS 2 makes multiple preparations for a handover, and/or saves or updates modification information of the coverage modification cell, and/or saves or retrieves a MRO status of a modified cell. That is, the BS 2 may operate for avoiding connection or re-establishment failure during the cell re-configuration based on the information on coverage modification received from the BS 1. The BS 2 saves information of a serving cell to be added or information on a serving cell to be modified. The BS 2 saves the status information of the coverage modification cell. In the method of the present disclosure, there may be three approaches for the BS 2 to learn whether the information on coverage modification is a notification before coverage modification or a notification after coverage modification. That is, there may be three approaches for the BS 2 to learn whether the information on coverage modification indicates pre-notification of cell re-configuration or post-notification of the cell re-configuration. Approach 1: the BS 2 may learn whether the received information on coverage modification is a notification before coverage modification or a notification after coverage modification according to whether the received information on coverage modification contains a coverage deployment status indication. If a coverage deployment status indication is contained and a value thereof is “pre-notification” or “potential deployment”, then the information on coverage modification is a notification before coverage modification. That is, the message including the information on coverage modification is for pre-notification of the cell re-configuration, when the information on coverage modification includes a cell deployment status indicator and the cell deployment status indicator indicates pre-change-notification or potential deployment. The cell deployment status indicator in the information on coverage modification indicates that a cell coverage status is planned to be used at next re-configuration. If a coverage deployment status indication is contained and a value thereof is “after modification”, or a coverage deployment status indication is not received, then the information on coverage modification is a notification after coverage modification. Approach 2: the BS 2 may learn whether the received information on coverage modification is a notification before coverage or a notification after coverage modification according to whether the received coverage modification information contains information elements of the list of associated cells of the coverage modification cell. If the information elements of the list of associated cells of the coverage modification cell are received, then the information on coverage modification is a notification before coverage modification. That is, the coverage modification is planned to be occurred at next re-configuration. Or if the information elements of the list of associated cells of the coverage modification cell are not received, then the information on coverage modification is a notification after coverage modification. Approach 3: the BS 2 learns whether the information on coverage modification received from the BS 1 is a notification before cell re-configuration or a notification after cell re-configuration according to a cell identity and a cell coverage status of the coverage modification cell. Corresponding to notification before coverage modification, the cell coverage status of the coverage modification cell is the same as an existing status. Being the same as an existing status means that the cell coverage status of the coverage modification cell is the same as a status of a corresponding cell saved by the BS 2 (e.g., both are either inactive, or active), or the cell coverage status of the coverage modification cell in the received information on coverage modification is inactive but currently the BS 2 has no information of a corresponding cell. Corresponding to notification after coverage modification, the cell coverage status of the coverage modification cell received by the BS 2 is different from a status of the coverage modification cell saved by the BS 2. In step 402, when the information on coverage modification includes a notification before coverage modification, then the BS 2 makes multiple preparations for a handover. That is, the BS 2 may operate for avoiding connection or re-establishment failure during the cell re-configuration based on the information on coverage modification received from the BS 1. When the BS 2 initiates a handover of the UE to a cell of the BS 1, the BS 2 contains information of the coverage modification cell in re-establishing information of a handover request, which case may be implemented in a cell shaping scenario; or when the BS 2 initiates the handover of the UE to the cell of the BS 1, it may contain information on a cell in the inactive status among coverage modification cells in the re-establishment information of the handover request; or when the BS 2 initiates the handover of the UE to the cell of the BS 1, it contains information of a cell newly added or modified and in the inactive status in the re-establishment information of the handover request; or when the BS 2 initiates a handover to a coverage modification cell, the BS 2 contains information of an associated cell in the inactive status or information of an associated cell among the coverage modification cells in re-establishment information of a handover request. In this way, if during a handover, a cell of the BS 1 is re-configured, the method provides that the re-establishment of the UE is successful in a cell in the active status after re-configuration, and avoids a re-establishment failure. When the information on coverage modification contains a notification after coverage modification, the BS 2 retrieves a MRO status of a cell in the active status, saves an ECGI and a MRO status of a cell in the inactive status. The BS 2 can know that the BS 1 may have released a PCI of the cell in the inactive status. The BS 2 may release the PCI information of the cell in the inactive status. The present disclosure will be described in details hereinafter by detailed embodiments, in which the BS 1 is a BS which controls a coverage modification cell, and the BS 2 is a BS that has an X2 interface with the BS 1 or a neighboring BS of the BS 1. The BS controls a cell with modified coverage. FIG. 5 illustrates a first self-optimization method which supports a cell coverage modification scenario according to embodiments of the present disclosure. The flow is applicable for notification before cell coverage modification. As shown in FIG. 5, the flow includes the following process. Step 501, the BS 1 notifies information on cell coverage modification of the BS 1 to the BS 2. The information on cell coverage modification includes a coverage deployment status indication and/or an associated cell of the coverage modification cell. When the coverage deployment status indication is a potential deployment status indication, then the information on cell coverage modification is a notification before coverage modification. That is, a message including the information on coverage modification is for pre-notification of the cell re-configuration, when the information on coverage modification includes a cell deployment status indicator and the cell deployment status indicator indicates pre-change-notification or potential deployment. The cell deployment status indicator in the information on coverage modification indicates that a cell coverage status is planned to be used at next re-configuration. The BS 1 may let the BS 2 know the information on cell coverage modification is a notification before coverage modification by an implicit approach, a detail process of which is the same as that in step 301, and will not be elaborated herein. In step 501, the information on cell coverage modification includes one or more kinds of following information: a cell identity of the cell with modified coverage, i.e., an ECGI; a cell coverage status of the cell with modified coverage; cell replacing information related to the cell with modified coverage; a coverage deployment status indication of the cell with modified coverage, i.e., indicating whether the information on coverage modification is a pre-notification of cell re-configuration or post-notification. That is, the information on coverage modification may include a cell identity of the coverage modification cell, i.e., an ECGI; a cell coverage status of the coverage modification cell; a list of associated cells of the coverage modification cell; a coverage deployment status indication of the coverage modification cell, i.e., indicating whether the information on cell coverage modification is a notification before coverage modification or a notification after coverage modification. The information on coverage modification comprises cell replacing information related to the cell with modified coverage, when the information on coverage modification includes the cell deployment status indicator. The cell deployment status indicator in the information on coverage modification indicates that the cell coverage status is planned to be used at next re-configuration. In step 501, the cell coverage status is configured to indicate whether the coverage modification cell is in the inactive status or in the active status, and when the coverage modification cell is in the active status, different values corresponding to different cell coverage status. The list of associated cells of the coverage modification cell refers to one or more cells as follows. For example, if a coverage modification cell is cell B, and a cell which is associated with the cell B is cell A, then the cell A and the cell B may have common, or overlapped, or adjacent coverage when they are active. For example, in a situation where cell C can be split into cell D and cell E, a cell which is associated with the cell D and the cell E is the cell C. In a situation where cell X and cell Y can be merged as cell Z, cells which are associated with the cell Z are the cell X and the cell Y. For cell shaping, e.g., re-configuration of cell H, if a coverage area of the cell H is changed due to cell shaping of the cell H, and the change of the coverage area of the cell H needs neighboring cell M and cell N to change their coverage, or needs compensation by coverage of the neighboring cell M and cell N, the cell M and the cell N are associated cells of the cell H. Corresponding to the situation where the cell C under the BS 1 is to be split into the cell D and the cell E, corresponding to notification before the cell splitting, information of the cell D and the cell E will be contained in information of served cell to be added sent from the BS 1 to the BS 2. The information on cell coverage modification contains the cell D and the cell E, and status of the cell D and cell E are inactive. The associated cell of both the cell D and the cell E is the cell C. The information on cell coverage modification contains an indication of potential deployment or pre-notification. If after establishment of the X2 interface between the BS 1 and the BS 2, it is the first time that the cell C is to be split into the cell D and the cell E, i.e., information of the cell D and the cell E having not been notified to the BS 2, then the information of the cell D and the cell E will be contained in information of served cells to be added sent from the BS 1 to the BS 2. If it is not the first time that the cell C is to be split into the cell D and the cell E, i.e., the information of the cell D and the cell E having been notified to the BS 2, then the information of the cell D and the cell E will be contained in information of served to be modified cells sent from the BS 1 to the BS 2. The BS 1 may re-allocate resources such as PCIs for the cell D and the cell E. Step 502, the BS 2 receives the information on cell coverage modification. The BS 2 saves received information, and the BS 2 saves information of served cells to be added or information of served cells to be modified. The BS 2 saves status information of a coverage modification cell. The BS 2 saves information of an associated cell of a cell in the inactive status. For a serving cell to be modified, the BS 2 uses received information to cover previously saved information of the serving cell. The BS 2 may know that the received information on cell coverage modification is a notification before coverage modification by three approaches, a detail procedure of which is similar to that in step 402, and will not be elaborated herein. The BS 2 makes multiple preparations for a handover according to the received information on cell coverage modification. That is, the BS 2 may operate for avoiding connection or re-establishment failure during the cell re-configuration based on the information on coverage modification received from the BS 1. When the BS 2 initiates a handover to a cell of the BS 1, it may contain information of a coverage modification cell in re-establishment information of a handover request, which case for example may be applicable for the cell shaping scenario; or when the BS 2 initiates a handover to a cell of the BS 1, it may contain information of a cell in the inactive status among coverage modification cells in re-establishment information of a handover request; or when the BS 2 initiates a handover of the UE to a cell of the BS 1, it may contain information of a cell newly added or modified and in the inactive status in re-establishment information of a handover request; or when the BS 2 initiates a handover to a coverage modification cell, the BS 2 contains information of an associated cell in the inactive status or information of an associated cell among the coverage modification cells in re-establishment information of a handover request. In this way, if during a handover, a cell of the BS 1 is re-configured, the method provides that the re-establishment of the UE is successful in a cell in the active status after re-configuration, and avoid a re-establishment failure. In step 402, for a cell in the inactive status contained in the cell coverage modification list, the BS 2 may not initiate a handover to it. For example, in a scenario where the cell C is split into the cell D and the cell E, the BS 2 receives the information from the BS 1. When the BS 2 initiates a handover of the UE to the cell C, it may contain information of the cell D and the cell E in re-establishment information of a handover request message. In this way, if during the handover, the cell C is split into the cell D and cell E, and the handover fails, the method provide successful re-establishment of the UE to the cell D or to the cell E. Corresponding to a scenario of cell shaping, e.g., re-configuration of the cell H, coverage of the cell H is changed due to cell shaping of the cell H, and the coverage change needs the neighboring cell M and cell N to change their coverage, or needs compensation by coverage of the neighboring cell M and cell N, the cell M and the cell N being associated cells of the cell H. When the BS 2 initiates a handover of the UE to the cell H, it may contain information of the cell M and the cell N in re-establishment information of a handover request message. In this way, if during the handover, the cell H is shaped, and the handover fails, the method provide successful re-establishment of the UE to the cell M or to the cell N. If the BS 2 initiates a handover of UE to a cell of the BS 1, the BS 2 may contain information of a cell newly added or modified and in the inactive status, or a cell in the inactive status among coverage modification cells, or a coverage modification cell in re-establishment information of a handover request message. In this way, in case of a handover failure of the UE to the cell of the BS 1, if during the handover, a coverage modification cell is re-configured, the method provides success of re-establishment of the UE to a re-configured cell, and avoid re-establishment failure. For example, in the scenario where the cell C is split into the cell D and the cell E, the BS 2 receives the information from the BS 1. When the BS 2 initiates a handover of UE to the cell C of the BS 1, it may contain the information of the cell D and the cell E in re-establishment information of a handover request message. In this way, if during the handover, the cell C of the BS 1 is split into the cell D and the cell E, and for the UE in coverage of the cell D or in coverage of the cell E, the handover fails, the method provides successful re-establishment of the UE to the cell D or to the cell E. Corresponding to the scenario of cell shaping, e.g., re-configuration of the cell H, coverage of the cell H is changed due to cell shaping of the cell H, and the coverage change needs the neighboring cell M and cell N to change their coverage, or needs compensation by coverage of the neighboring cell M and cell N, the cell M and the cell N being associated cells of the cell H. When the BS 2 initiates a handover of the UE to the cell H, it may contain information of the cell M and the cell N in re-establishment information of a handover request message. In this way, if during the handover, the cell H is shaped, and for the UE under coverage of the cell M or under coverage of the cell N, the handover fails, the method provides successful re-establishment of the UE to the cell M or to the cell N. According to any approach described in step 402, the BS 2 knows that the information on cell coverage modification received from the BS 1 is a notification before coverage modification, and the BS 2 does not release resources such as a PCI of a cell in the inactive status. Till this point, description of the flowchart of the first self-optimization method which supports the cell coverage modification scenario provided according to embodiments of the present disclosure is completed. The method enables a BS to learn the status of a cell of a neighboring BS, which solves the problem of re-establishment failure of a radio resource connection, solves the problem of MRO, better uses system resources and radio resources, and better sets measurements and performs a handover. FIG. 6 illustrates a second self-optimization method which supports a cell coverage modification scenario provided according to embodiments of the present disclosure. The flow may be used for notification after cell coverage modification. As shown in FIG. 6, the flow includes the following process. Step 601, BS 1 notifies BS 2 of information on cell coverage modification of the BS 1. The information on cell coverage modification does not contain a coverage deployment status indication, which indicates that the information on cell coverage modification is a notification after coverage modification, and the BS 1 releases resources, e.g., a PCI of a cell in the inactive status. The BS 1 saves an ECGI of the cell in the inactive status. The BS 1 may let the BS 2 know the information on cell coverage modification is a notification after coverage modification by an implicit approach, and a detailed process of which is the same as that in step 301, and will not be elaborated herein. In the step 601, the information on cell coverage modification includes one or more kinds of following information: a cell identity of a cell with modified coverage, i.e., an ECGI; a cell
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