Method and system for operating cells in an overlay network including macro cells and home cells

A method and system for operating cells in a network where macro cells and home cells coexist are provided. The method includes determining a first set of neighbor macro Base Stations (BSs) located within a predefined reference distance from a new macro BS to be newly installed, determining a second set of neighbor macro BSs having a cell region overlapping a region of a serving cell served by the new macro BS, detecting at least one sector including a contact with the cell region of the new macro BS within a cell region of each of the neighbor macro BSs in the second set, determining a neighbor cell set including the detected at least one sector, generating an initial Neighbor Relation Table (NRT) by mapping information about each of neighbor cells included in the neighbor cell set, IDentifiers (IDs) of neighbor macro BSs serving the neighbor cells, and a Physical Resource Cell IDentifier (PCID) allocated to each of the neighbor macro BSs, and providing the initial NRT to the new macro BS as neighbor BS information.

PRIORITY

This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Nov. 6, 2009 and assigned Serial No. 10-2009-0106947, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and system for operating cells in an overlay network where macro cells and home cells coexist.

2. Description of the Related Art

With the development of communication technology and the increasing deployment of multimedia technology, a variety of mass transfer technologies have been applied to mobile communication systems, and one of their key issues is an increase in wireless capacity. The increase in wireless capacity may be achieved in various ways. For example, more frequencies may be allocated to increase the wireless capacity, but this is impracticable because of the finiteness of the frequency resources. Therefore, a method of more efficiently using the limited frequency resources is required, and for the efficient use of the limited frequency resources, a method of increasing the frequency utilization efficiency and a method of miniaturizing service cells may be considered. In particular, the cell miniaturizing method can provide a plurality of User Equipments (UEs) with the wireless environment where abundant higher-quality resources are available, thereby enabling high-capacity services.

Unlike the conventional Base Station (BS) or Node B (hereinafter referred to as a ‘macro BS’), a BS, which provides communication services to a small number of UEs existing in a home cell region or a micro communication region such as an independent office, a residence and a building, is defined as a home Node B or a home BS. A plurality of home BSs serving an arbitrary home cell region exist in a macro cell region served by the macro BS. The home cell may connect a mobile phone to the Internet, providing Fixed Mobile Convergence (FMC) services or combined wire/wireless services at low cost.

In the conventional communication system, if powered on by a user, the home BS operates in a receive mode like the UE, instead of transmitting data in a downlink time period, and measures signal strengths of neighbor BSs. Based on the collected information, the home BS determines the neighbor BSs depending on Frequency Assignment (FA), transmit power, and BS information. The neighbor BSs are used to make a list of candidate BSs subjected to handover attempt. The list of neighbor BSs may be set in a manual manner proposed by a mobile network operator, or may be automatically set based on signal measurement.

While the macro BS is installed by the mobile network operator, the home BS is installed or uninstalled by the user, making it difficult for the macro BS to manually update each home BS in its neighbor BS list.

Typically, once installed, a new macro BS generates installation parameters associated with its internal configuration by itself. However, in all operation steps, if the new macro BS identifies neighbor BSs based on only the signals measured by UEs and includes in the neighbor BS list the BSs, measured signals of which satisfy a specific condition, without making a list of initial neighbor BSs, then the home BS is not considered, resulting in the neighbor BS list being inaccurate.

A conventional macro BS is allocated one Physical resource Cell IDentifier (PCID) within a limited range. The PCID allocated to the macro BS should be set not to be identical to those of BSs included in the list of neighbor BSs of the macro BS. However, if the home BS and the macro BS use the same PCID because a PCID of the macro BS is allocated without considering the home BSs, PCID collision may occur between BSs.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide a method and system for allocating Physical resource Cell IDentifiers (PCIDs) in an overlay environment where macro cells and home cells coexist.

Another aspect of the present invention is to provide a method and system for generating an initial Neighbor Relation Table (NRT) and providing it to a macro Base Station (BS) during initial installation of the macro BS.

Another aspect of the present invention is to provide a method and system for initially installing a macro BS considering characteristics of home cells.

Another aspect of the present invention is to provide a method and system for allocating to a macro BS a PCID being different from those of BSs, included in lists of neighbor BSs, during initial installation of the macro BS.

In accordance with an aspect of the present invention, a method for operating cells in a network where macro cells and home cells coexist is provided. The method includes determining a first set of neighbor macro BSs located within a predefined reference distance from a new macro BS to be newly installed, determining a second set of neighbor macro BSs having a cell region overlapping a region of a serving cell served by the new macro BS, detecting at least one sector including a contact with a cell region of the new macro BS within a cell region of each of the neighbor macro BSs in the second set, and determining a neighbor cell set including the detected at least one sector, generating an initial NRT by mapping information about each of neighbor cells included in the neighbor cell set, IDentifiers (IDs) of neighbor macro BSs serving the neighbor cells, and a PCID allocated to each of the neighbor macro BSs, and providing the initial NRT to the new macro BS as neighbor BS information.

In accordance with another aspect of the present invention, a method for operating cells in a network where macro cells and home cells coexist is provided. The method includes generating a macro PCID black list including a PCID allocated to each of neighbor macro BSs for a new macro BS to be newly installed, generating a home PCID black list including PCIDs of neighbor home BSs located within a serving cell region of the new macro BS, determining whether there is at least one remaining PCID, except for PCIDs included in the macro PCID black list and the home PCID black list, among allocable PCIDs, and allocating the at least one remaining PCID to the new macro BS in the presence of at least one remaining PCID.

In accordance with further another aspect of the present invention, a system for operating cells in a network where macro cells and home cells coexist is provided. The system includes a home BS management system for receiving information about a new macro BS to be newly installed, from a macro BS management system, and for managing neighbor home BSs located in a region of a serving cell of the new macro BS based on the information about the new macro BS, and the macro BS management system for determining a first set of neighbor macro BSs located within a predefined reference distance from the new macro BS, for determining a second set of neighbor macro BSs having a cell region overlapping the region of the serving cell served by the new macro BS, for detecting at least one sector including a contact with a cell region of the new macro BS within a cell region of each of the neighbor macro BSs in the second set, for determining a neighbor cell set including the detected at least one sector, generates an initial NRT by mapping information about each of neighbor cells included in the neighbor cell set, IDs of neighbor macro BSs serving the neighbor cells, and a PCID allocated to each of the neighbor macro BSs, and for providing the initial NRT to the new macro BS as neighbor BS information.

In accordance with yet another aspect of the present invention, a system for operating cells in a network where macro cells and home cells coexist is provided. The system includes a home BS management system for receiving information about a new macro BS from a macro BS management system, and for managing neighbor home BSs located within a serving cell region of the new macro BS based on the information about the new macro BS, and the macro BS management system for generating a home PCID black list including PCIDs of the neighbor home BSs, for receiving from the home BS management system, for generating a macro PCID black list including a PCID allocated to each of neighbor macro BSs of the new macro BS, for determining whether there is at least one remaining PCID, except for PCIDs included in the macro PCID black list and the home PCID black list, among allocable PCIDs, and for allocating the at least one remaining PCID to the new macro BS in the presence of at least one remaining PCID.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various to assist in that overall understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

In the following description, exemplary embodiments of the present invention may be roughly divided into the generation of an initial Neighbor Relation Table (NRT) and the allocation of a Physical resource Cell IDentifier (PCID) for a new macro Base Station (BS). More specifically, the exemplary embodiments may be roughly divided into three procedures. In a first procedure, in an overlay network where macro cells and home cells coexist, during initial installation of a new macro BS, PCIDs allocated to neighbor BSs located around the new macro BS are acquired, and an initial NRT is generated by mapping IDentifiers (IDs) of the neighbor BSs to their associated PCIDs. In addition, PCIDs included in the initial NRT are used to make a macro cell-based PCID black list (hereinafter referred to as a ‘macro PCID black list’) PCIDBL-macrorepresenting PCIDs unallocable to the new macro BS.

In a second procedure, PCIDs allocated to home cells located in a macro cell served by the new macro BS are used to make a home cell-based PCID black list (hereinafter referred to as a ‘home PCID black list’) PCIDBL-homerepresenting PCIDs unallocable to the new macro BS.

In a third procedure, one of the remaining PCIDs, except for PCIDs included in the PCIDBL-macroand the PCIDBL-homeamong all PCIDs, which are limited resources in the network, is allocated as a PCID of the new macro BS. In the absence of the remaining PCIDs, i.e., in the absence of PCIDs not allocated to any BSs, a PCID of a home BS located farthest from the new macro BS among the PCIDs included in the PCIDBL-homeis reallocated as a PCID of the new macro BS. A PCID of a home BS using the reallocated PCID may also be reallocated.

Now, the first to third procedures will be described in detail with reference to the accompanying drawings.

FIG. 1shows a schematic configuration of a network where macro cells and home cells coexist, according to an exemplary embodiment of the present invention. It should be noted that the network configuration shown inFIG. 1is given as a mere example, and the present invention is not limited to the example shown inFIG. 1.

Referring toFIG. 1, the network includes a cell planning system110(or an upper network), a home BS management system110for managing a plurality of home BSs, a macro BS management system120for managing a plurality of macro BSs, home BSs #1˜#n140-1˜140-n, and a macro BS150. The macro BS150represents a new macro BS to be initially installed in the network, and the home BSs #1˜#n140-1˜140-nrepresent home BSs located in a macro cell region served by the macro BS150, or located in the other regions.

The cell planning system100provides the macro BS management system120with information for generating an initial NRT of the macro BS150. The initial NRT stores mapping information between IDs of neighbor BSs and PCIDs allocated to the neighbor BSs. The information for generating the initial NRT includes, for example, latitude/longitude, transmit/receive power, and antenna direction of the macro BS150.

The macro BS management system120includes an initial NRT generator122, a macro cell database124, a macro NRT database126, a PCID allocator128, and a PCID information database130.

The initial NRT generator122generates an initial NRT of the macro BS150through the first procedure. The macro cell database124stores information about neighbor macro cells, especially location information such as latitudes and longitudes. The macro NRT database126stores PCIDs allocated to the macro cells whose information is stored in the macro cell database124. Based on the information for generating the initial NRT, the initial NRT generator122acquires information about neighbor BSs from the macro cell database124, acquires PCID information allocated to the acquired neighbor BSs from the macro NRT database126, and delivers the acquired information to the PCID allocator128.

The PCID allocator128makes a macro PCID black list with PCIDs of macro BSs included in the initial NRT, and stores the macro PCID black list in the PCID information database130.

The home BS management system110includes a home cell database112, a PCID allocator114, and a controller116. The home cell database112stores information about the home cells located in a macro cell region served by the macro BS150. The PCID allocator114delivers information about home BSs located in a region of the macro cell served by the macro BS150, and PCID information allocated to the home BSs, to the PCID allocator128through the second procedure.

Then, the PCID allocator128makes a home PCID black list with the PCIDs allocated to the home BSs and stores the home PCID black list in the PCID information database130. Upon recognizing that the macro BS150uses the same PCID as that of any one of its home BSs #1˜#n140-1˜140-n, the controller116controls the PCID allocator114to reallocate a PCID of the home BS that uses the same PCID.

1. First Procedure

Now, the first procedure will be described in detail with reference toFIGS. 2 to 4. The first procedure includes detecting neighbor macro BSs of a new macro BS being initially installed, which satisfy a specific condition, and generating an initial NRT in which IDs of the detected neighbor macro BSs are mapped to PCIDs of the detected neighbor macro BSs.

FIG. 2shows how to select reserve neighbor BSs constituting an initial NRT of an initially installed new macro BS according to an exemplary embodiment of the present invention.

Referring toFIG. 2, a macro BS #N200is a new macro BS to be initially installed in a network where macro cells and home cells coexist, and a macro BS #i210is one of the neighbor BSs located within a predefined distance from the macro BS #N200. A macro cell #N205represents a service coverage area of the macro BS #N200, and a macro cell #i215represents a service coverage area of the macro BS #i210. For example, a radius of the service coverage area may be determined based on a power level at which transmission by each BS is possible, or determined by a selection made by a system operator considering the surrounding geographical environment.

A first condition in the first procedure is that a neighbor BS should be located within a predefined reference distance from the macro BS #N200. A distance between the macro BS #N200and the neighbor macro BS may be simply calculated based on location information of each BS, i.e., latitude and longitude. For example, the reference distance may be set to be two or three times the distance between the macro BS #N200and its nearest macro BS. It should be noted that the reference distance is herein set to a specific number by way of example only, and is not limited thereto.

The initial NRT generator122acquires location information of the macro BS #N200, i.e., latitude and longitude, received from an upper network, and based thereon, retrieves location information of neighbor macro BSs from the macro cell database124. Through the retrieval, the initial NRT generator122acquires information about reserve neighbor BSs, which are macro BSs located within the predefined distance from the macro BS #N200. Equation (1) represents the first condition.
DNi<DN(iεSnode)  Equation (1)
where DNdenotes the reference distance, DNidenotes a distance between the macro BS #N200and a macro BS #i, i denotes an indicator of a macro BS, and Snodedenotes a set of all macro BSs.

That is, the macro BS #i210is selected as a reserve neighbor BS of the macro BS #N200, since the macro BS #i210is located within the distance DNfrom the macro BS #N200, satisfying Equation (1).

If a set SwithinDof reserve neighbor BSs satisfying the first condition is determined, the initial NRT generator122retrieves information about neighbor macro BSs satisfying a second condition among the reserve neighbor BSs included in SwithinD, from the macro cell database124. More specifically, through the retrieval, the initial NRT generator122acquires, from among the reserve neighbor BSs, reserve neighbor BSs satisfying the second condition given to determine whether the neighbor BSs are located in a cell overlapping a region of the macro cell205served by the macro BS #N200as defined in Equation (2) below. That is, if a sum of a radius of the macro cell #N205and a radius of the macro cell #i215is greater than a distance between the macro BS #N200and the macro BS #i210, the macro cell #i215is considered to be located in a region overlapping the macro cell #N205.

As shown inFIG. 2, the macro BS #i210is located in the macro cell #±215overlapping the macro cell #N205satisfying Equation (2).
DNi<RN+Ri(iεSoverlay)  Equation (2)
where RNdenotes a radius of the macro BS #N200, Ridenotes a radius of the macro BS #i210, and Soverlaydenotes a set of reserve neighbor BSs satisfying Equation (2).

If Soverlayof reserve neighbor BSs satisfying the second condition is determined, the initial NRT generator122retrieves information about sectors satisfying a third condition among sectors of the reserve neighbor BSs included in Soverlay, from the macro cell database124. Through the retrieval, the initial NRT generator122acquires sectors including contacts Piand Qiwhere the macro cells205and215overlap.

FIG. 3shows how to select reserve neighbor BSs included in an initial NRT using contacts of a region overlapping a macro cell of an initially installed new macro BS according to an exemplary embodiment of the present invention.

Referring toFIG. 3, it is assumed that a macro BS #N300is being initially installed in a network where macro cells and home cells coexist, and a macro BS #i310is one of reserve neighbor BSs included in a set Soverlayfor the macro BS #N300. The macro cell #N305represents a service coverage area of the macro BS #N300, and the macro cell #i315represents a service coverage area of the macro BS #i310. The macro cell #i315is divided into three sectors Ci0, Ci1, Ci2.

The initial NRT generator122retrieves information about sectors satisfying the third condition among sectors constituting each of the reserve neighbor BSs included in Soverlay, from the macro cell database124. The third condition is defined as Equations (3) and (4) using contacts Piand Qi, respectively, where a region of the macro cell #N305and a region of the macro cell #i315overlap.
θp⊂θ(Ci1)  Equation (3)
where θ(Ci1) denotes an angular degree range for a sector Ci1in the region of the macro cell #i315.

Equation (3) is a condition for selecting a sector based on the contact Pi. More specifically, the initial NRT generator122detects an angular degree θpfrom a reference direction320of the macro cell #i315to the contact Pi within the region of the macro cell #i315, and detects a sector #1325including the angular degree θpwithin the region of the macro cell #i315. The initial NRT generator122acquires information about the sector #1325from the macro cell database124. The reference direction320, a preset reference, may be the due north for example.

The initial NRT generator122acquires sectors including the first contact Piamong the sectors constituting each of the reserve neighbor BSs included in Soverlay, and a set of the acquired sectors is defined as Cip.

Next, Equation (4) below is a condition for selecting sectors based on the second contact Qi.
θQ⊂θ(Ci2)  Equation (4)
where θ(Ci2) denotes an angular degree range for a sector Ci2in the region of the macro cell #i315. The initial NRT generator122detects an angular degree θQfrom the reference direction320to the contact Qiwithin the region of the macro cell #i315, and detects a sector #2330including the angular degree θQwithin the region of the macro cell #i315. In addition, the initial NRT generator122acquires information about the sector #2330from the macro cell database124.

The initial NRT generator122acquires sectors including the second contact Qiamong the sectors constituting each of the reserve neighbor BSs included in Soverlay, and a set of the acquired sectors is defined as Ciq.

After acquiring Cipand Ciq, the initial NRT generator122determines a set of the sectors in the Cipand Ciqas a neighbor cell set Cneighborof the macro BS #N300. That is, the initial NRT generator122determines neighbor cells included in the Cneighboras the final neighbor BSs included in the initial NRT, acquires PCID information allocated to the determined neighbor BSs included in the initial NRT, from the macro NRT database126, and transmits the acquired PCID information to the PCID allocator128. Then, the PCID allocator128generates an initial NRT by mapping IDs of the final neighbor BSs to PCIDs of the final neighbor BSs, and transmits the generated initial NRT to the macro BS150. In this way, the macro BS150may acquire an initial NRT while initially installed in the overlay network.

The PCID allocator128generates a macro PCID black list PCIDBL-macro, a list of PCIDs unallocable to the macro BS150, using PCIDs included in the initial NRT, and stores the macro PCID black list PCIDBL-macroin the PCID information database130.

2. Second Procedure

Now, the second procedure will be described in detail.

FIG. 4shows home BSs located in a region of a macro cell served by a new macro BS in a network according to an exemplary embodiment of the present invention.

Referring toFIG. 4, a macro BS #N405represents a new macro BS being initially installed in a network where home cells and macro cells coexist, and a macro cell400represents a service coverage area of the macro BS #N405.

The home BS management system110receives information about the initially installed macro BS #N405from the macro BS management system120. The information about the macro BS #N405includes latitude and longitude information of the macro BS #N405, transmit power thereof, and a radius of the macro cell served by the macro BS150.

Based on a transmit power level of the macro BS #N405, the controller116detects a region of the macro cell400served by the macro BS #N405, and detects neighbor home cells, or micro cells located in the region of the macro cell400. Then, under the control of the controller116, the PCID allocator114acquires information about the detected neighbor home cells from the home cell database112, and transmits the acquired information to the PCID allocator128in the macro BS management system120. The information about the detected neighbor home cells includes IDs, PCIDs and latitude/longitude information of the home BSs serving the detected home cells.

Thereafter, the PCID allocator128generates a home PCID black list PCIDBL-homeby mapping PCIDs allocated to the neighbor home BSs serving the detected neighbor home cells, to IDs of the neighbor home BSs, and transfers the home PCID black list PCIDBL-hometo the PCID information database130.

3. Third Procedure

After acquiring PCIDBL-macroand PCIDBL-homethrough the first and second procedures, the PCID allocator128allocates a new PCID to the macro BS150.

For example, let's assume that the total number of PCIDs allocable by the macro BS management system120is 504 (#0˜#503). The PCID allocator128first determines whether the remaining PCIDs (hereinafter referred to as ‘new PCIDs’), except for the PCIDs included in PCIDBL-macroand PCIDBL-home, are present in the total of 504 PCIDs. In the presence of at least one new PCID, one of the at least one new PCID is allocated to the macro BS150.

If all the remaining PCIDs, except for the PCIDs included in PCIDBL-macro, are used in the neighbor home BSs included in PCIDBL-home, the PCID allocator128sorts the neighbor home BSs included in PCIDBL-homein descending order of the distance from the macro BS150. In addition, the PCID allocator128reallocates a PCID of the neighbor home BS located farthest from the macro BS150as a PCID of the macro BS150. Thereafter, the PCID allocator128notifies the home BS management system110of the information about the neighbor home BS that uses the same PCID as that of the macro BS150.

When reallocating the PCIDs used by the neighbor home BSs to macro BSs being newly installed, as described above, the PCID allocator128transmits to the home BS management system110a set Hinterfaceof the neighbor BSs that use the same PCIDs as those of the macro BSs. As described above, the PCID allocator128reallocates the PCID used by the neighbor home BS located farthest from the newly installed macro BS, since the PCID allocator128cannot allocate a new PCID to the new macro BS. However, due to the use of the same PCID, the macro BS and the neighbor home BS using the same PCID may suffer from interference. Accordingly, upon receiving Hinterface, the home BS management system110performs an operation of reallocating the PCIDs of the neighbor home BSs, included in Hinterface.

FIG. 5shows an operation of reallocating a PCID of a home BS according to an exemplary embodiment of the present invention.

Referring toFIG. 5, the home BS management system110receives information about a new macro BS from the macro BS management system120in step500. The information about the new macro BS includes latitude/longitude, transmit/receive power, and antenna direction of the new macro BS.

In step505, based on the information about the new macro BS, the home BS management system110retrieves information about neighbor home BSs located in a macro cell region served by the new macro BS, from the home cell database112. In step510, the home BS management system110transmits the retrieved information about the neighbor home BSs to the macro BS management system120.

In step515, the home BS management system110determines whether a list Hinterfaceof the neighbor home BSs using the same PCIDs as that of the new macro BS is received from the macro BS management system120. If so, the home BS management system110reallocates PCIDs of the neighbor home BSs included in Hinterfaceas new PCIDs, in step520. More specifically, the home BS management system110reallocates the remaining PCIDs, except for the PCID allocated to the new macro BS, to the neighbor home BSs. The PCID allocation may be performed to minimize possible PCID collisions between the neighbor home BSs and the existing macro BSs. The PCID allocation is outside the scope of the present disclosure and therefore a detailed description thereof will be omitted.

Meanwhile, the PCID allocation to the neighbor home BSs included in each of the macro BSs may be achieved as follows. Generally, the home cell regions are almost the same in size, and determined by the network operator. Therefore, the home BS management system110selects and allocates one of the remaining PCIDs, except for the PCID of the macro BS and the PCIDs of the home BSs, that exist in the home cell region of the relevant neighbor home BS. In the absence of the remaining PCIDs, in order to minimize the interference due to the use of the same PCID, the home BS management system110sorts the macro BS and the home BSs existing in the home cell region of the neighbor home BS in an order of distance from the neighbor home BS, and allocates a PCID of the farthest home BS to the neighbor home BS.

In step525, the home BS management system110checks whether at least one neighbor home BS, to which a PCID is reallocated, is providing a call service. If so, the home BS management system110waits until the call service is terminated in step540, and proceeds to step530after the service is terminated. However, if the neighbor home BS is not providing a call service, the home BS management system110reboots the neighbor home BS to reallocate the PCID thereto, in step530.

After completion of the rebooting of all the neighbor home BSs to which the PCIDs are reallocated, the home BS management system110transmits a PCID reallocation complete message to the macro BS management system120in step535.

Thereafter, upon receiving the PCID reallocation complete message, the macro BS management system120transmits a message for instructing the new macro BS to start providing a service using the allocated PCID. Upon receiving the message, the new macro BS starts the service. That is, in the case where a PCID of a neighbor home BS is reallocated to a new macro BS, the new macro BS starts providing a service after confirming that a new PCID is reallocated to the neighbor home BS which has used the reallocated PCID, instead of immediately providing the service after being reallocated to the PCID.

FIG. 6shows an operation of generating an initial NRT of a new macro BS by a macro BS management system according to an exemplary embodiment of the present invention.

Referring toFIG. 6, the initial NRT generator122in the macro BS management system120receives information about a new macro BS in step600. In step605, the initial NRT generator122determines a first condition or a first set consisting of reserve neighbor BSs located within a predefined reference distance from the new macro BS. The reference distance may be determined to be two or three times the distance between the new macro BS and the new macro BS's nearest macro BS. In step610, the initial NRT generator122determines a second condition or a second set consisting of reserve neighbor BSs located in a region overlapping a region of a cell served by the new macro BS among the reserve neighbor BSs included in the first set. In step615, the initial NRT generator122determines a third condition or determines, as neighbor cells, the sectors satisfying Equation (3) or Equation (4) using contacts with the cell served by the new macro BS, among the cells of the reserve neighbor BSs included in the second set. The initial NRT generator122generates an initial NRT by mapping IDs of macro BSs located in the determined neighbor cells to PCIDs allocated to the macro BSs in step620, and transfers the initial NRT to the PCID allocator128in step625. Then, the PCID allocator128generates a macro PCID black list including the PCIDs allocated to the macro BSs included in the initial NRT, and transmits the macro PCID black list to the new macro BS150.

FIG. 7shows an operation of allocating a PCID to a new macro BS by a macro BS management system according to an exemplary embodiment of the present invention.

Referring toFIG. 7, the PCID allocator128in the macro BS management system120receives neighbor home cell information from the home BS management system110in step700. The neighbor home cell information includes IDs of neighbor home BSs located in a region of a macro cell served by a new macro BS, and PCIDs allocated to the neighbor home BSs. In step705, the PCID allocator128generates and stores a home PCID black list including PCIDs of the neighbor home BSs included in the neighbor home cell information.

In step710, the PCID allocator128determines whether there is at least one or more remaining PCIDs or new PCIDs, except for the PCIDs included in the macro PCID black list and the home PCID black list. In the presence of a new PCID(s), the PCID allocator128allocates one of the at least one new PCIDs to the new macro BS in step715.

In the absence of the new PCID, the PCID allocator128sorts the neighbor home BSs in descending order of distance from the new macro BS in step720. In step725, the PCID allocator128reallocates a PCID of the neighbor home BS farthest from the new macro BS, to the new macro BS.

In step730, the PCID allocator128transmits to the home BS management system110a list of at least one neighbor home BS that uses the same PCID as that of the new macro BS.

In step735, the PCID allocator128checks whether a reboot complete message, indicating that each of the neighbor home BSs has completed its rebooting after being reallocated a new PCID, has been received from the home BS management system110. If the reboot complete message has not been received, the PCID allocator128waits for the reboot complete message in step740.

However, upon receipt of the reboot complete message, the PCID allocator128transmits a service start message instructing the new macro BS to start the service in step745. In this way, in the overlay network where macro cells and home cells coexist, a new macro BS is initially installed considering home cell information, thereby enabling its PCID to be allocated without collision between BSs.

As is apparent from the foregoing description, in an overlay network where macro cells and home cells coexist, during initial installation of a new macro BS, an initial NRT is generated by mapping IDs of neighbor BSs of the new macro BS to PCIDs of the neighbor BSs, and transmitted to the new macro BS, thereby minimizing interference between macro and/or home BSs during PCID allocation and making it possible to provide high-quality service and reduce operating costs of the network operator.