Abstract:
A method and apparatus for avoiding a collision of an uplink preamble using a cell identifier. In a case of installing a new small-sized base station in a mobile communication system, the method and apparatus may set a code parameter, a time parameter, and a frequency parameter, differently from a neighboring small-sized base station using the cell identifier even when dedicatedly using a preamble in a contention-free scheme to avoid a collision of the preamble, so that a random access preamble may be managed without occurrence of the collision with the neighboring small-sized base stations.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority benefit of Korean Patent Application No. 10-2009-0128074, filed on Dec. 21, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    One or more embodiments relate to a method and apparatus for avoiding a collision of an uplink preamble using a cell identifier (ID), and more particularly, to a method and apparatus which may avoid a collision of an uplink preamble, in a case of newly installing a base station in a mobile communication system, by configuring a random access preamble, that is, a signature that may automatically perform an uplink synchronization and a radio resource acquirement when being initially operated or while being operated, without occurrence of a collision with neighboring cells. 
         [0004]    2. Description of the Related Art 
         [0005]    In a mobile communication system, particularly, in a Long Term Evolution (LTE) system of a 3rd Generation Partnership Project (3GPP), a terminal may generally perform a random access process, so that the terminal may access a network. By performing the random access process via the network by the terminal, an initial access, a handover, and the like may be realized. 
         [0006]    The random access process may be classified into a contention scheme and a contention-free scheme, and a difference between the two schemes may be whether a random access preamble is dedicatedly assigned to a terminal to be used. Specifically, in the contention-free scheme, since a unique terminal and a unique preamble are used, a collision may not occur. In the contention scheme, since a preamble randomly selected by the terminal is used, at least two terminals may use an identical preamble, and thus a probability of occurrence of the collision may increase. 
         [0007]    However, even in the contention-free scheme, in a case where a large number of femto cells is present within a macro cell, code parameters, time parameters, and frequency parameters between neighboring cells may be the same when a limited preamble resource is dedicatedly used, resulting in occurrence of the collision. 
       SUMMARY 
       [0008]    One or more embodiments provide a method and apparatus of avoiding a collision of an uplink preamble using a cell identifier. 
         [0009]    One or more embodiments also provide a method and apparatus of avoiding a collision of an uplink preamble using a cell identifier in a newly installed or deployed small-sized base station. 
         [0010]    One or more embodiment also provide a method and apparatus of avoiding a collision of an uplink preamble by setting a preamble parameter of a small-sized base station newly installed or deployed in an Operation Administration Maintenance (OAM), differently from neighboring small-sized base stations adjacent to the small-sized base station, using cell identifiers of the neighboring small-sized base stations. 
         [0011]    According to an aspect of one or more embodiments, there may be provided an apparatus for avoiding a collision of a preamble in a small-sized base station, the apparatus including: a neighboring cell identifying unit to collect a cell identifier of a neighboring cell to verify presence/absence of the neighboring cell and to identify the neighboring cell; a mapping database to store predetermined parameters corresponding to each of predetermined cell identifiers; a cell identifier allocation unit to select, from the mapping database, a cell identifier unused in neighboring cells, and to allocate the selected cell identifier to a corresponding small-sized base station; and a parameter setting unit to verify, in the mapping database, parameters corresponding to the allocated cell identifier, and to set the verified parameters as parameters of the preamble. 
         [0012]    According to another aspect of one or more embodiments, there may be provided an apparatus for avoiding collision of a preamble in a small-sized base station, the apparatus including: a neighboring cell identifying unit to collect a cell identifier of a neighboring cell to verify presence/absence of the neighboring cell and to identify the neighboring cell; a parameter requesting unit to generate a parameter request message requesting a setting of parameters and including the cell identifier of the neighboring cell, and to transmit the generated parameter request message to an OAM; and a parameter setting unit to verify an allocated cell identifier included in a parameter response message and parameters corresponding to the allocated cell identifier when receiving the parameter response message from the OAM, and to set a preamble using the verified parameters. 
         [0013]    According to still another aspect of one or more embodiments, there may be provided an apparatus for avoiding collision of a preamble in an OAM, the apparatus including: a parameter request reception unit to verify a cell identifier of a neighboring cell included in a parameter request message when receiving the parameter request message from a small-sized base station being incapable of independently setting a parameter; a mapping database to store predetermined parameters corresponding to each of predetermined cell identifiers; a cell identifier allocation unit to select, from the mapping database, a cell identifier unused in neighboring cells, and to allocate the selected cell identifier to a corresponding small-sized base station; and a parameter response processing unit to verify, in the mapping database, parameters corresponding to the allocated cell identifier, to generate a parameter response message including the allocated cell identifier and the parameters corresponding to the allocated cell identifier, and to transmit the generated parameter response message to the small-sized base station. 
         [0014]    According to yet another aspect of one or more embodiments, there may be provided a method for avoiding a collision of a preamble in a small-sized base station, the method including: collecting a cell identifier of a neighboring cell to verify presence/absence of neighboring cells, and to identify the neighboring cell; selecting, from a mapping database where predetermined parameters corresponding to each of predetermined cell identifiers are stored, a cell identifier unused in neighboring cells, and allocating the selected cell identifier to the small-sized base station; and verifying, in the mapping database, parameters corresponding to the allocated cell identifier, and setting the verified parameters as parameters of the preamble. 
         [0015]    According to further aspect of one or more embodiments, there may be provided a method for avoiding a collision of a preamble in a small-sized base station, the method including: collecting a cell identifier of a neighboring cell to verify presence/absence of the neighboring cells, and to identify the neighboring cell; generating a parameter request message including the cell identifier of the neighboring cell requesting a setting of parameters, transmitting the generated parameter request message; and verifying an allocated cell identifier included in the parameter request message and parameters corresponding to the allocated cell identifier when receiving a parameter response message from an OAM; and setting the preamble using the verified parameters. 
         [0016]    According to further aspect of one or more embodiments, there may be provided a method for avoiding collision of a preamble in an OAM, the method including: verifying a cell identifier of a neighboring cell included in a parameter request message when receiving the parameter request message from a small-sized base station being incapable of independently setting a parameter; selecting, from a mapping database where predetermined parameters corresponding to each of predetermined cell identifiers are stored, a cell identifier unused in neighboring cells, and allocating, to the small-sized base station, the selected cell identifier as a cell identifier of the small-sized base station; verifying, in the mapping database, parameters corresponding to the allocated cell identifier; and generating a parameter response message including the allocated cell identifier and parameters corresponding to the allocated cell identifier, and transmitting the generated parameter response message to the small-sized base station. 
         [0017]    Additional aspects of embodiments will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the disclosure. 
       EFFECT 
       [0018]    According to an embodiment, to avoid a collision of a preamble when newly installing a base station in a mobile communication system, a cell identifier that is not allocated to neighboring small-sized base stations may be selected using predetermined parameters for each cell identifier, and the collision of the preamble may be avoided using a parameter corresponding to the selected cell identifier. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    These and/or other aspects will become apparent and more readily appreciated from the following description of embodiments, taken in conjunction with the accompanying drawings of which: 
           [0020]      FIG. 1  illustrates a configuration of a mobile communication system according to an embodiment; 
           [0021]      FIG. 2  illustrates a configuration of a femto base station of  FIG. 1  that avoids a collision of a preamble; 
           [0022]      FIG. 3  illustrates a configuration of the femto base station of  FIG. 1  that avoids a collision of a preamble, and a configuration of an Operation Administration Maintenance (OAM) of  FIG. 1 ; 
           [0023]      FIG. 4  is a flowchart illustrating a process of avoiding a collision of a preamble in a small-sized base station according to an embodiment; 
           [0024]      FIG. 5  is a flowchart illustrating a process of avoiding a collision of a preamble by requesting a parameter, in a small-sized base station according to an embodiment; and 
           [0025]      FIG. 6  is a flowchart illustrating a process of allocating parameters to avoid a collision of a preamble in an OAM according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. Embodiments are described below to explain the present disclosure by referring to the figures. 
         [0027]    Embodiments of the invention may relate to a method and apparatus of avoiding a collision of a preamble using cell identifiers of neighboring small-sized base stations adjacent to a newly installed or deployed small-sized base station, by differently setting a preamble parameter of the newly installed or deployed small-sized base station from the neighboring small-sized base stations. 
         [0028]      FIG. 1  illustrates a configuration of a mobile communication system according to an embodiment. In  FIG. 1 , a relation between a newly deployed base station, used for preventing a collision of a preamble, and peripheral devices is illustrated. For convenience of description, a small-sized base station may be referred to as a femto base station, however, is not limited thereto. Referring to  FIG. 1 , a femto base station  120  included in a newly installed or deployed small-sized base station may collect, from a terminal  122  within a cell area of the femto base station  120  or peripheral devices such as a macro base station  110  and femto base stations  130 ,  140 , and  150 , Physical Cell Identifiers (PCIs), that is, cell identifiers of neighboring small-sized base stations adjacent to the newly installed or deployed small-sized base station. 
         [0029]    The femto base station  120  may collect PCIs of neighboring cells through a specific interface with the peripheral devices. Alternatively, the femto base station  120  may collect the PCIs of the neighboring cells by receiving System Information Block (SIB) from the femto base stations  130 ,  140 , and  150  controlling the neighboring cells  130 ,  140 , and  150 . The femto base station  120  may identify the neighboring cells using the PCIs of the neighboring cells. 
         [0030]    The femto base station  120  included in the newly installed or deployed small-sized base station may select a PCI that is not used in the neighboring cells, using predetermined parameters for each of the PCIs, that is, the cell identifiers, and may allocate a preamble set using parameters corresponding to the selected PCI. 
         [0031]    An Operation Administration Maintenance (OAM)  160  may manage the PCI, that is, the cell identifier of each of the small-sized base stations, and set and transmit the PCI and parameters corresponding to the PCI when receiving a request for a setting of parameters from a small-sized base station that fails to perform a setting of parameters. 
         [0032]      FIG. 2  illustrates a configuration of the femto base station  120  of  FIG. 1  that avoids a collision of a preamble according to an embodiment. In  FIG. 2 , the small-sized base station that may set parameters being capable of independently avoiding the collision of the preamble is illustrated. Referring to  FIG. 2 , the femto base station  120 , that is, a small-sized base station includes a neighboring cell identifying unit  210 , a cell identifier allocation unit  212 , a mapping database (DB)  214 , a parameter setting unit  216 , and a communication unit  220 . 
         [0033]    The neighboring cell identifying unit  210  may collect a cell identifier of a neighboring cell to verify presence/absence of the neighboring cell and to identify the neighboring cell. The neighboring cell identifying unit  210  may collect the cell identifier of the neighboring cell, through a specific interface, from a peripheral device such as a macro base station and a femto base station or from a terminal within a cell area of the femto base station  120 . Alternatively, the neighboring cell identifying unit  210  may receive a System Information Block (SIB) from the terminal within the cell area or the peripheral device, and may acquire the cell identifier of the neighboring cell from the SIB. As the cell identifier, a Physical Cell Identifier (PCI) may be used. 
         [0034]    The mapping DB  214  may store predetermined parameters corresponding to each of predetermined cell identifiers. In this instance, the predetermined parameters may include code parameters, time parameters, and frequency parameters. 
         [0035]    The cell identifier allocation unit  212  may select, from the mapping DB  214 , a cell identifier unused in neighboring cells, using the cell identifier of the neighboring cell obtained in the neighboring cell identifying unit  210 , and may allocate the selected cell identifier to a corresponding small-sized base station. 
         [0036]    The cell identifier allocation unit  212  may transmit, to the OAM  160 , information about the allocated cell identifier. 
         [0037]    The parameter setting unit  216  may verify, in the mapping DB  214 , parameters corresponding to the allocated cell identifier obtained in the cell identifier allocation unit  212 , and set the verified parameters as parameters of the preamble. 
         [0038]    The communication unit  220  may receive the cell identifier of the neighboring cell from the neighboring cell, and transmit the allocated cell identifier to the OAM  160 . 
         [0039]      FIG. 3  illustrates a configuration of the femto base station  120  of  FIG. 1  that avoids a collision of a preamble, and a configuration of the OAM  160  of  FIG. 1 . In  FIG. 3 , the femto base station  120  that may not set parameters being capable of independently avoiding the collision of the preamble, and the OAM  160  that may set the parameters being capable of independently avoiding the collision of the preamble are illustrated. 
         [0040]    Referring to  FIG. 3 , in a case of a small-sized base station, that is, the femto base station  120 , that may not independently set parameters, the femto base station  120  includes a neighboring cell identifying unit  310 , a parameter requesting unit  312 , a parameter setting unit  314 , and a communication unit  320 . 
         [0041]    The neighboring cell identifying unit  310  may collect a cell identifier of a neighboring cell to verify presence/absence of the neighboring cell, and to identify the neighboring cell. The neighboring cell identifying unit  310  may collect the cell identifier of the neighboring cell, through a specific interface, from a terminal within a cell area of the femto base station  120  or a peripheral device such as a macro base station and a femto base station. Alternatively, the neighboring cell identifying unit  210  may receive an SIB from the terminal within the cell area or the peripheral device, and may obtain the cell identifier of the neighboring cell from the SIB. As the cell identifier, a PCI may be used. 
         [0042]    The parameter requesting unit  312  may generate a parameter request message requesting a setting of parameters for the cell identifier and the preamble, and transmit the generated parameter request message to the OAM  160  via the communication unit  320 . In this instance, the parameter request message may include the cell identifier of the neighboring cell. 
         [0043]    The parameter setting unit  314  may verify an allocated cell identifier included in a parameter response message and parameters corresponding to the allocated cell identifier when receiving the parameter response message from the OAM  160 , and may set parameters to be used for a preamble. The set parameters may include code parameters, time parameters, and frequency parameters. 
         [0044]    The communication unit  320  may receive the cell identifier of the neighboring cell from the neighboring cell, transmit the parameter request message to the OAM  160 , and receive the parameter response message from the OAM  160 . 
         [0045]    The OAM  160  being capable of setting a parameter includes a parameter requesting reception unit  330 , a cell identifier allocation unit  332 , a mapping DB  334 , a parameter response processing unit  336 , and a communication unit  340 . 
         [0046]    When receiving a parameter request message from a small-sized base station being incapable of independently setting the parameter, the parameter request reception unit  330  may verify a cell identifier of a neighboring cell included in the parameter request message. 
         [0047]    The mapping DB  334  may store predetermined parameters corresponding to each of predetermined cell identifiers. In this instance, the predetermined parameters may include code parameters, time parameters, and frequency parameters. 
         [0048]    The cell identifier allocation unit  332  may select, from the mapping DB  334 , a cell identifier unused in a neighboring cell using the cell identifier of the neighboring cell verified in the parameter requesting reception unit  330 , and allocate the selected cell identifier to a corresponding small-sized base station. 
         [0049]    The parameter response processing unit  336  may verify, in the mapping DB  334 , parameters corresponding to the cell identifier allocated in the cell identifier allocation unit  332 . The parameter response processing unit  336  may generate the parameter response message including the allocated cell identifier and parameters corresponding to the allocated cell identifier, and transmit the generated parameter response message to a small-sized base station requesting the parameters via the communication unit  340 . 
         [0050]    The communication unit  340  may provide a communication connection with small-sized base stations. 
         [0051]    Hereinafter, a method of avoiding a collision of an uplink preamble using a cell identifier will be described with reference to  FIGS. 4 and 5 . 
         [0052]      FIG. 4  is a flowchart illustrating a process of avoiding a collision of a preamble in a small-sized base station according to an embodiment. 
         [0053]    Referring to  FIG. 4 , in operation  410 , a small-sized base station that may set parameters capable of independently avoiding the collision of the preamble may determine whether occurrence of an event configuring the preamble is detected. In operation  412 , when the occurrence of the event is detected in operation  410 , the small-sized base station may collect a cell identifier of a neighboring cell to verify presence/absence of the neighboring cell and to identify the neighboring cell. 
         [0054]    In operation  414 , the small-sized base station may select, from the mapping DB where the parameters corresponding to the cell identifier is predetermined, a cell identifier corresponding to a preamble where the collision does not occur, and allocate the selected cell identifier to a corresponding small-sized base station. 
         [0055]    In operation  416 , the small-sized base station may retrieve, from the mapping DB, frequency parameters, time parameters, and code parameters corresponding to the selected cell identifier, and set a preamble using the retrieved parameters. In operation  418 , the small-sized base station may transmit the allocated cell identifier to the OAM. 
         [0056]      FIG. 5  is a flowchart illustrating a process of avoiding a collision of a preamble by requesting a parameter, in a small-sized base station according to an embodiment. 
         [0057]    Referring to  FIG. 5 , in operation  510 , a small-sized base station that may not set parameters capable of independently avoiding the collision of the preamble may determine whether occurrence of an event configuring the preamble is detected. In operation  512 , when the occurrence of the event is detected in operation  510 , the small-sized base station may collect a cell identifier of a neighboring cell to verify presence/absence of the neighboring cell and to identify the neighboring cell. 
         [0058]    In operation  514 , the small-sized base station may transmit, to an OAM, a parameter request message including information about the cell identifier of the neighboring cell. 
         [0059]    In operation  516 , the small-sized base station may determine whether a parameter response message is received from the OAM. In operation  518 , when the parameter response message is received from the OAM, the small-sized base station may store a cell identifier included in the parameter response message. In operation  520 , the small-sized base station may set the preamble using frequency parameters, time parameters, and code parameters which are included in the parameter response message. 
         [0060]      FIG. 6  is a flowchart illustrating a process of allocating parameters to avoid a collision of a preamble in an OAM according to an embodiment. 
         [0061]    Referring to  FIG. 6 , in operation  610 , an OAM that may set parameters capable of independently avoiding the collision of the preamble may determine whether a parameter request message is received from a small-sized base station incapable of setting parameters. In operation  612 , when the parameter request message is received from the small-sized base station, the OAM may identify a cell identifier of a neighboring cell included in the parameter request message. 
         [0062]    In operation  614 , the OAM may select, from the mapping DB where parameters corresponding to the cell identifier are predetermined, a cell identifier corresponding to a preamble where the collision does not occur. 
         [0063]    In operation  616 , the OAM may transmit, to a corresponding small-sized base station, a parameter response message including the cell identifier and frequency parameters, time parameters, and code parameters corresponding to the cell identifier. 
         [0064]    The methods according to the above-described embodiments may be recorded in computer-readable non-transitory storage media including program instructions to implement various operations embodied by a computer. The media may also include, alone or in combination with the program instructions, data files, data structures, and the like. Examples of computer-readable non-transitory media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD ROM disks and DVDs; magneto-optical media such as optical disks; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory (ROM), random access memory (RAM), flash memory, and the like. Examples of program instructions include both machine code, such as produced by a compiler, and files containing higher level code that may be executed by the computer using an interpreter. The described hardware devices may be configured to act as one or more software modules in order to perform the operations of the above-described embodiments, or vice versa. 
         [0065]    Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined by the claims and their equivalents.