Abstract:
Provided is a method and apparatus for avoiding a collision of a preamble in a base station. When a new base station is installed in a mobile communication system and in this instance, an exclusive preamble using a contention-free scheme is employed to avoid a preamble collision, at least one of a code parameter, a time parameter, and a frequency parameter used in a preamble of the new base station may be set to be different from a code parameter, a time parameter, and a frequency parameter used in a preamble of a neighboring cell, whereby it is possible to manage a random access preamble without causing a collision between cells.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2009-0075641, filed on Aug. 17, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     Embodiments of the present invention relate to a method and apparatus for avoiding a collision of a preamble in a base station, and more particularly, to a method and apparatus for avoiding a collision that may construct a random access preamble, which is a signature that may automatically obtain an uplink synchronization and a radio resource in an initial stage or in an operation, when a new base station is installed in a mobile communication system, without causing a collision between cells. 
     2. Description of the Related Art 
     In a mobile communication system, in particular, in a 3 rd  Generation Partnership Project (3GPP) Long Term Evolution (LTE) system, a terminal may generally perform a random access process for an access to a network. The terminal may perform the random access process to the network for initial access, handover, and the like. 
     The random access process may employ a contention scheme and a contention-free scheme. A difference between the contention scheme and the contention-free scheme lies in whether the terminal exclusively designates and uses a random access preamble. Specifically, in the case of the contention-free scheme, since a different preamble is used for a different terminal, a collision may not occur. In the case of the contention scheme, since the terminal uses a randomly selected preamble, at least two terminals may simultaneously use the same preamble and thus a collision may occur. 
     Even in the case of the contention-free scheme, when a large number of femtocells exist within a macro cell and a limited amount of preamble resources are used, a collision may occur due to the same code parameter, the time parameter, and the frequency parameter that are used between cells. 
     SUMMARY 
     An aspect of the present invention provides a method and apparatus for avoiding a collision of a preamble in a base station. 
     Another aspect of the present invention also provides a method and apparatus for avoiding a collision that may set a parameter used in a preamble of a newly installed or provided base station to be different from a parameter used in a preamble of a neighboring cell. 
     According to an aspect of the present invention, there is provided an apparatus for avoiding a collision of a preamble in a base station, the apparatus including: a neighboring cell identifier to collect neighboring cell information in order to determine whether a neighboring cell exists, and in order to identify the neighboring cell; a parameter collector to collect a code parameter, a time parameter, and a frequency parameter that are used in a preamble of the neighboring cell; and a parameter setting unit to set at least one of a code parameter, a time parameter, and a frequency parameter that are used in a preamble of the base station to be different from the code parameter, the time parameter, and the frequency parameter that are used in the preamble of the neighboring cell, when setting the code parameter, the time parameter, and the frequency parameter that are used in the preamble of the base station. 
     According to another aspect of the present invention, there is provided a method of avoiding a collision of a preamble in a base station, the method including: collecting neighboring cell information in order to determine whether a neighboring cell exists, and in order to identify the neighboring cell; collecting a code parameter, a time parameter, and a frequency parameter that are used in a preamble of the neighboring cell; and setting at least one of a code parameter, a time parameter, and a frequency parameter that are used in a preamble of the base station to be different from at the code parameter, the time parameter, and the frequency parameter that are used in the parameter of the neighboring cell, when setting the code parameter, the time parameter, and the frequency parameter that are used in the preamble of the base station. 
     Effect 
     According to embodiments of the present invention, when installing a new base station in a mobile communication system, an exclusive preamble may be employed using a contention-free scheme in order to avoid a preamble collision. By setting a code parameter, a time parameter, and a frequency parameter to be different between cells, it may be possible to avoid the preamble collision. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects, features, and advantages of the invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a diagram illustrating a configuration of a mobile communication system according to an embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating a configuration of an apparatus for avoiding a collision of a preamble in a base station according to an embodiment of the present invention; and 
         FIG. 3  is a flowchart illustrating a process of avoiding a collision of a preamble in a base station according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. Exemplary embodiments are described below to explain the present invention by referring to the figures. 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. When it is determined detailed description related to a known function or configuration may render the purpose of the present invention unnecessarily ambiguous in describing the present invention, the detailed description will be omitted herein. 
     According to an embodiment of the present invention, there is provided a method and apparatus for avoiding a collision that may set a parameter used in a preamble of a newly installed or provided base station to be different from a parameter used in a preamble of a neighboring cell. 
       FIG. 1  is a diagram illustrating a configuration of a mobile communication system according to an embodiment of the present invention. A relationship between a newly installed base station and peripheral devices to avoid a preamble collision can be seen from  FIG. 1 . Referring to  FIG. 1 , a newly installed or provided femto base station  120  may collect neighboring cell information from a terminal  122  within a cell coverage of the femto base station  120  or a peripheral device, for example, a macro base station  110 , and femto base stations  130 ,  140 , and  150 . 
     The newly installed or provided femto base station  120  may collect the neighboring cell information using a particular interface with the peripheral device. Also, the newly installed or provided femto base station  120  may receive a system information block from the femto base stations  130 ,  140 , and  150  managing the neighboring cell, to thereby collect the neighboring cell information. The femto base station  120  may identify the neighboring cell based on the neighboring cell information. 
     The newly installed or provided femto base station  120  may collect, from an Operation, Administration, Maintenance (OAM)  160 , a code parameter, a time parameter, and a frequency parameter that are used in a preamble of the neighboring cell, and then allocate a random access preamble to prevent a preamble collision. 
     Although the OAM  160  is described herein as a device managing the code parameter, the time parameter, and the frequency parameter used in the preamble of the neighboring cell, the present invention is not limited thereto. Specifically, any device managing parameters may be applicable. 
       FIG. 2  is a block diagram illustrating a configuration of an apparatus for avoiding a collision of a preamble in a base station according to an embodiment of the present invention. Referring to  FIG. 2 , the femto base station  120  may include a neighboring cell identifier  210 , a parameter collector  220 , a parameter setting unit  230 , and a communication unit  240 . 
     The neighboring cell identifier  210  may collect neighboring cell information in order to verify whether a neighboring cell exists, and in order to identify the neighboring cell. The neighboring cell identifier  210  may collect the neighboring cell information from a terminal within a cell coverage of the femto base station  120  or a peripheral device, for example, a macro base station and a femto base station via a particular interface. Also, the neighboring cell identifier may receive a system information block from the terminal within the cell coverage or the peripheral device, to thereby obtain the neighboring cell information from the system information block. 
     The parameter collector  220  may collect, from the OAM  160  or the peripheral device, a code parameter, a time parameter, and a frequency parameter that are used in a preamble of the neighboring cell, using the neighboring cell information. 
     When setting a code parameter, a time parameter, and a frequency parameter that are used in a preamble of the femto base station  120 , the parameter setting unit  230  may set at least one of the code parameter, the time parameter, and the frequency parameter used in the preamble of the femto base station  120  to be different from the code parameter, the time parameter, and the frequency parameter that are used in the neighboring cell. By setting the at least one parameter used in the femto base station  120  to be different from the neighboring cell, a preamble collision may be prevented. 
     The communication unit  240  may provide a communication with the terminal within the cell coverage of the base station  120 , a neighboring base station, the OAM, and a parameter administration maintenance unit (not illustrated). 
     The communication unit  240  may receive the neighboring cell information from the terminal within the cell coverage and the peripheral device. The communication unit  240  may receive, from the OAM  160  or the parameter administration maintenance, the code parameter, the time parameter, and the frequency parameter that are used in the preamble of the neighboring cell. The communication unit  240  may transmit the set code parameter, the time parameter, and the frequency parameter to the OAM or the parameter administration maintenance. 
     Hereinafter, a method of avoiding a collision of a preamble in a base station will be described. 
       FIG. 3  is a flowchart illustrating a process of avoiding a collision of a preamble in a base station according to an embodiment of the present invention. 
     Referring to  FIG. 3 , when the base station detects an occurrence of an event constituting the preamble in operation  310 , and the base station may collect neighboring cell information in operation  312 , the base station may collect neighboring cell information to verify whether a neighboring cell exists, and to identify the neighboring cell. 
     The base station may collect the neighboring cell information from a terminal within a cell coverage of the base station or a neighboring device via a particular interface. Also, the base station may obtain the neighboring cell information from a system information block received from the terminal within the cell coverage or the peripheral device. 
     In operation  314 , the base station may collect a code parameter, a time parameter, and a frequency parameter that are used in a preamble of the neighboring cell, from an OAM or a parameter administration maintenance using the collected neighboring cell information. 
     In operation  316 , the base station may set at least one of a code parameter, a time parameter, and a frequency parameter that are used in a preamble of the base station to be different from the code parameter, the time parameter, and the frequency parameter that are used in the preamble of the neighboring cell. 
     In operation  318 , the base station may transmit, to the OAM or the parameter administration maintenance, the set code parameter, the time parameter, and the frequency parameter that are used in the preamble of the base station, and thereby register the set code parameter, the time parameter, and the frequency parameter. 
     The above-described exemplary embodiments of the present invention may be recorded in computer-readable 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 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 exemplary embodiments of the present invention, or vice versa. 
     Although a few exemplary embodiments of the present invention have been shown and described, the present invention is not limited to the described exemplary embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.