KR101498296B1 - Method of processing hierarchy cell information in wireless communication system - Google Patents

Abstract

A method of processing hierarchical cell information in a hierarchical cell structure wireless communication system in which a small range of cells are overlapped in a wide range of cells includes receiving a first synchronization signal including a cell identifier, Wherein the period of the first synchronization signal is fixed and the second synchronization signal is detected during a period of the first synchronization signal, wherein the second synchronization signal is generated after the first synchronization signal is transmitted And a cell ID included in the first synchronization signal is an ID of the wide range cell and the second synchronization signal is a synchronization signal transmitted from the cell of the small range.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of processing hierarchical cell information in a wireless communication system,

The present invention relates to wireless communications, and more particularly to a method for processing cell information in a hierarchical cell structure.

With the development of communication and the spread of multimedia technology, various high-capacity transmission technologies have been applied to wireless communication systems. There is a method of allocating more frequency resources as a method for increasing radio capacity, but there is a limit to allocating more frequency resources to a plurality of users with limited frequency resources. One of the ways to use limited frequency resources more efficiently is to make the cell smaller. If the size of the cell is made small, the number of users that one base station should service is reduced, so that the base station can allocate more frequency resources to the user. If the size of the cell is made small, it is possible to provide a large capacity service in a better state to a large number of users.

Recently, femto-cell technology installed in homes and offices has been actively researched. The femtocell refers to a small mobile communication base station used in the home or office. The femtocell is connected to an IP network that is installed in a home or office, and provides mobile communication services by accessing a core network of a mobile communication system through an IP network. A user of a mobile communication system can receive a service through an existing macrocell in an outdoor environment and a service through a femtocell in an indoor environment. The femtocell improves the indoor coverage of the mobile communication system by supplementing the existing macrocell service in the building and improves the coverage of the mobile communication system, Of voice and data services.

A co-channel scheme, a partial co-channel scheme, and a dedicated channel scheme are available for allocating the frequency bands of the femtocell located within the cell coverage of the macrocell. The co-channel scheme allocates the same frequency band as the macrocell to the frequency band of the femtocell, and it is important to control the transmission power of the femtocell to reduce the interference that may occur when the macrocell and the femtocell use the same frequency band. In the partial co-channel scheme, some frequency bands of the macrocell are allocated to a common channel used together with the femtocell. When interference occurs in the co-channel, the macrocell user receives the service through the frequency band other than the common channel. Interference can be reduced. In the dedicated channel scheme, the macrocell and the femtocell use different frequency bands. However, the interference between the macrocell and the femtocell can be greatly mitigated, but the limited frequency resource may not be efficiently used.

A femtocell is a personal base station installed in a home or an office, and a large number of femtocells can be installed in a densely populated area. Accordingly, not only the interference with the macrocell but also the interference between the femtocells can be greatly increased. In addition, since the cell ID uses a predetermined number of sequences, all the cell IDs can be used in an area where the femtocell is concentrated, and a cell ID can not be assigned to any more femtocells. To increase the number of cell IDs, the length of the sequence used as the cell IDs can be increased, but the overhead increases by the sequence length of the increased cell IDs.

A method of efficiently transmitting a cell ID of a macrocell and a femtocell is required.

SUMMARY OF THE INVENTION The present invention provides a method of processing a cell ID in a hierarchical cell structure.

A method of processing hierarchical cell information in a hierarchical cell structure wireless communication system in which a small range of cells are overlapped in a wide range of cells according to an aspect of the present invention includes a first synchronization And detecting a second synchronous signal during a period of the determined first synchronous signal, wherein the second synchronous signal has a first period of the first synchronous signal, Wherein a cell ID included in the first synchronization signal is an ID of the wide range cell and the second synchronization signal is transmitted after a predetermined offset after the synchronization signal is transmitted, Signal.

Cell information can be efficiently transmitted in a hierarchical cell structure.

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, a typical wireless communication system includes a user equipment (UE) and a base station (BS). A terminal may be fixed or mobile and may be referred to by other terms such as a Mobile Station (MS), a User Terminal (UT), a Subscriber Station (SS), a wireless device, A base station generally refers to a fixed station that communicates with a terminal and may be referred to by other terms such as a Node-B, a Base Transceiver System (BTS), an Access Point, and so on.

One base station may have more than one cell.

The BS may be divided into a femto BS 20 and a macro BS 60 according to the cell coverage or the allocation scheme. The cell of the femto base station 20 is smaller than the cell of the macro base station 60. [ All or a part of the cells of the femto base station 20 may overlap with the cells of the macro base station 60. [ In this manner, a structure in which a small range of cells are overlapped within a wide range of cells is referred to as a hierarchy cell structure.

The femto base station 20 may be referred to as a femto-cell, a home node-B, or a closed subscriber group (CSG). The macro base station 60 may be called a macro-cell in a manner different from the femtocell.

The femto base station 20 is connected to the femto gateway 30 via the Iuh interface. The Iuh interface means an interface between the femto base station 20 and the femto gateway 30 via the IP network. The femto gateway 30 is an entity that manages at least one femto base station 20. The femto gateway 30 can perform the registration, authentication, and security procedures of the femto base station 20 so that the femto base station 20 can access the core network 90 of the wireless communication system. The macro base station 60 is connected to an RNC (radio network control) 70 via an Iub interface. The RNC 70 manages at least one macro base station 60 and connects the macro base station 60 to the core network 90. The macro base station 60 is connected to the core network 90 through a leased line, while the femto base station 20 is connected to the core network 90 through the IP network.

A terminal connected to the femto base station 20 is referred to as a femto terminal 10 and a terminal connected to the macro base station 60 is referred to as a macro terminal 50. [ The femto terminal 10 can be a macro terminal 50 through handover to a macro base station and the macro terminal 50 can be a femto terminal 10 through handover to a femto base station.

Hereinafter, downlink refers to transmission from a base station to a terminal, and uplink refers to communication from a terminal to a base station. In the downlink, the transmitter may be part of the base station, and the receiver may be part of the terminal. In the uplink, the transmitter may be part of the terminal, and the receiver may be part of the base station.

There are no restrictions on multiple access schemes applied to wireless communication systems. Such as CDMA (Code Division Multiple Access), TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access), SC-FDMA (Single-Carrier FDMA), and Orthogonal Frequency Division Multiple Access (OFDMA) .

Fig. 2 shows an example of a frame structure. And may be a frame structure of at least one of a macro cell and a femtocell in a hierarchical cell structure.

Referring to FIG. 2, a superframe includes a superframe header and four frames F0, F1, F2, and F3. The size of each super frame is 20 ms, and the size of each frame is 5 ms, but the present invention is not limited thereto. The superframe header can be placed first in the superframe, and is assigned a common control channel. The common control channel is a channel used for transmitting control information that can be commonly used by all terminals in a cell, such as information on frames constituting a super frame or system information. A synchronization channel for transmitting a synchronization signal within the superframe header or adjacent to the superframe header may be arranged. The synchronization signal may represent cell information such as a cell ID.

One frame includes eight subframes (Subframe, SF0, SF1, SF2, SF3, SF4, SF5, SF6, SF7). Each subframe may be used for uplink or downlink transmission. The subframe may be composed of 6 or 7 OFDM symbols, but this is only an example. A TDD (Time Division Duplexing) scheme or an FDD (Frequency Division Duplexing) scheme may be applied to the frame. In the TDD scheme, each subframe is used for uplink transmission or downlink transmission at different times at the same frequency. That is, the subframes in the TDD frame are divided into the uplink subframe and the downlink subframe in the time domain. In the FDD scheme, each subframe is used for uplink transmission or downlink transmission at different frequencies of the same time. That is, subframes in a frame of the FDD scheme are divided into an uplink subframe and a downlink subframe in the frequency domain. The uplink transmission and the downlink transmission occupy different frequency bands and can be performed at the same time.

The subframe includes at least one frequency partition. The frequency partition is composed of at least one physical resource unit (PRU). The frequency partition may include a Localized PRU and / or a Distributed PRU. The frequency block may be used for other purposes such as partial frequency reuse (FFR) or multicast and broadcast services (MBS).

A PRU is defined as a basic physical unit for resource allocation that includes a plurality of consecutive OFDM symbols and a plurality of consecutive subcarriers. The number of OFDM symbols included in the PRU may be equal to the number of OFDM symbols included in one subframe. For example, when one surframe is composed of six OFDM symbols, the PRU can be defined as 18 subcarriers and 6 OFDM symbols. A Logical Resource Unit (LRU) is a basic logical unit for distributed resource allocation and localized resource allocation. The LRU is defined as a plurality of OFDM symbols and a plurality of subcarriers, and includes pilots used in the PRU. Therefore, the number of suitable subcarriers in one LRU depends on the number of allocated pilots.

A Logical Distributed Resource Unit (DRU) may be used to obtain frequency diversity gain. The DRU includes subcarrier groups distributed in one frequency band. The size of the DRU is equal to the size of the PRU. The minimum unit forming the DRU is one subcarrier.

A Logical Contiguous Resource Unit (CRU) may be used to obtain a frequency selective scheduling gain. The CRU includes a local subcarrier group. The size of the CRU is equal to the size of the PRU.

3 shows another example of the frame structure. And may be a frame structure of at least one of a macro cell and a femtocell in a hierarchical cell structure.

Referring to FIG. 3, a radio frame is composed of 10 subframes, and one subframe may include two slots. One slot may comprise a plurality of OFDM symbols in the time domain. The number of OFDM symbols included in one slot can be variously determined according to the CP structure. In a radio frame using a general CP size, one OFDM symbol may be included in one slot. In the 10ms radio frame, when the OFDM symbol is 2048 Ts, the general CP size may be 144 Ts (Ts = 1 / (15000 * 2048) sec).

The P-SCH (Primary Synchronization Channel) is located in the last OFDM symbol of the 0th slot and the 10th slot. The same PSS (Primary Synchronization Signal) is transmitted through the two P-SCHs. The P-SCH is used to obtain time domain synchronization and / or frequency domain synchronization such as OFDM symbol synchronization, slot synchronization, and the like. The Zadoff-Chu (ZC) sequence can be used as the PSS, and the wireless communication system has at least one PSS.

The S-SCH (Secondary Synchronization Channel) is located immediately before the last OFDM symbol of the 0th slot and the 10th slot. The S-SCH and the P-SCH may be located in contiguous OFDM symbols. Different secondary synchronization signals (SSS) are transmitted through the two S-SCHs. The S-SCH is used to obtain frame synchronization and / or cell CP configuration, i.e., usage information of a general CP or an extended CP. One S-SCH uses two SSSs. The m-sequence can be used in SSS. That is, one m-sequence is included in one S-SCH. For example, when one S-SCH includes 63 subcarriers, two m-sequences of length 31 are mapped to one S-SCH.

The P-SCH and the S-SCH are used to obtain physical-layer cell identities (ID). The physical layer cell ID can be represented by 168 physical layer cell ID groups and three physical layer IDs belonging thereto. That is, the total physical layer cell ID is 504, represented by a physical layer cell ID group having a range of 0 to 167 and a physical layer ID having a range of 0 to 2 included in each physical layer cell ID group. Three ZC sequence root indexes indicating the physical layer ID are used for the P-SCH, and 168 m-sequence indexes representing the physical layer cell ID group can be used for the S-SCH.

The P-BCH (Physical-Broadcast Channel) is located in the 0th subframe in the radio frame. The P-BCH starts from the third OFDM symbol of the 0th subframe (starting from the 0th OFDM symbol) and occupies four OFDM symbols except for the P-SCH and the S-SCH. The P-BCH is used to obtain basic system configuration information of the base station. The P-BCH may have a period of 40 ms.

Now, a method of transmitting cell information in a hierarchical cell structure will be described. In a hierarchical cell structure, a wide range of cells is referred to as a macrocell, and a small range of cells belonging to the macrocell is referred to as a femtocell. However, the present invention is not limited to macrocells and femtocells, and macrocells and femtocells can be called various terms in a system that performs similar functions. For example, a femtocell may correspond to a pico-cell having a cell range larger than a femtocell and smaller than a macrocell, or a relay station that directly transmits a signal of a macrocell.

The femtocell ID can be configured by (1) using a certain sequence used as an existing macrocell ID as a femtocell ID, and (2) providing a separate sequence for a femtocell ID. The macrocell ID and the femtocell ID can use the same type of sequence and can be transmitted through the synchronization channel of the same transmission period. The UE detects a sequence of a cell ID transmitted through a synchronization channel and identifies whether the received cell ID sequence belongs to a sequence of a macro cell ID or a femtocell ID sequence. In this case, there is a limitation on the sequence of the macrocell ID and the femtocell ID, and interference between the synchronization signal of the macrocell and the synchronization signal of the femtocell may be increased.

When a certain sequence used as an existing macro-cell ID is used as a femtocell ID, the UE can access the currently connected cell in the same manner as the macrocell without distinguishing whether it is a femtocell or not. Therefore, the parameters and requirements of the system designed for the macro cell can be used as it is for the femtocell. On the other hand, when a separate sequence for the femtocell ID is provided, the UE can know whether the connected cell or neighboring cell is a macro cell or a femtocell through the cell search. In this case, the terminal can appropriately select system parameters and requirements supported by the macrocell and the femtocell. That is, although it is difficult to further optimize the femtocell in the method of using a certain sequence used as the femtocell ID as the existing macrocell ID, in the method of providing a separate sequence for the femtocell ID, Can be optimized and operated.

As illustrated in FIG. 2, a cell ID may be transmitted through one synchronization channel, and a cell ID may be transmitted through two or more synchronization channels as illustrated in FIG. The synchronization channel may be composed of at least one OFDM symbol. A case where a waveform of one cell ID is transmitted through one synchronization channel is referred to as a synchronization signal of a non-hierarchy structure. A case where a waveform of two or more cell IDs is transmitted through one synchronization channel or two or more synchronization channels is referred to as a synchronous signal of a hierarchical structure. The synchronization signal of the hierarchical structure may include different information and may be transmitted. The UE can distinguish the non-hierarchical synchronous signal and the hierarchical synchronous signal through the cell search.

When a femtocell ID is predefined and used such as using a certain sequence used as an existing macrocell ID as a femtocell ID or providing a separate sequence for a femtocell ID, The cell ID may become insufficient. If the number of sequences of the cell ID is increased to prevent the lack of the cell ID, additional interference may occur between the synchronization signals in the cell search process of the UE. In addition, there is a problem that the cell coverage of the femtocell must be reduced in order to transmit more information through the limited synchronization channel and reduce the interference. Therefore, there is a need for a method that can transmit the femtocell ID without affecting the cell coverage of the macrocell or the adjacent femtocell.

The proposed method is a method of transmitting a femtocell ID using the sufficient radio resources of the femtocell while minimizing the influence on the arrangement structure of the macrocell. According to the co-channel scheme or the partial co-channel scheme, the femtocell can use all or some of the radio resources used by the macrocell, whereas the number of the femtocell-supported UEs is very small compared to the macrocell. For example, a macrocell is designed assuming that it supports hundreds of users, but a femtocell is designed assuming that it supports fewer than 10 users. Therefore, the femtocell is less burdensome to the UE and various overhead reduction techniques can be applied. In the proposed method, the cell ID can be transmitted through the synchronization signal of the hierarchical structure, and the sequence used as the macro cell ID can be used as the group ID of the femtocell. That is, one or more femtocells belonging to the femtocell group can commonly use the macrocell ID. The femtocell group ID may be the same as or different from the macrocell ID. When the femtocell group ID is equal to the macrocell ID, the terminal receiving the service from the macrocell can receive the service from the macrocell without being affected by the femtocell. On the other hand, if the femtocell group ID is different from the macrocell ID, the terminal receiving the service from the macrocell may have difficulty in detecting the macrocell ID by the femtocell group ID. If access to the femtocell is allowed for all terminals, the terminal connected to the macrocell can receive the service without being affected by the femtocell, but it is possible to reduce the interference between the femtocells or provide sufficient information for handover between the femtocells There is no problem. The proposed method enables a femtocell ID to be transmitted while minimizing the influence on a macrocell in a macrocell having a wide cell area and a femtocell having a small cell area (including a pico cell, a relay station, etc.) associated therewith.

FIG. 4 illustrates a method of transmitting a macrocell ID and a femtocell ID according to an embodiment of the present invention.

Referring to FIG. 4, when a macrocell ID and a femtocell ID are the same, a synchronization channel of a femtocell is allocated to an offset position defined in a synchronization channel of a macrocell, so that a macrocell ID and a femtocell ID can be distinguished. That is, the synchronization signal of the macrocell and the synchronization signal of the femtocell can be transmitted in the same signal with the offset in the time domain. The synchronization signal of the macro cell may include cell information such as the macro cell ID. The synchronization signal of the femtocell may include cell information such as the femtocell ID. The synchronization signal of the macrocell and the synchronization signal of the femtocell can be transmitted with the same period so that the offset of the synchronization signal of the macrocell and the synchronization signal of the femtocell can be kept the same. The offset to which the sync signal of the femtocell is transmitted may be indicated in the sync signal or broadcast information of the macrocell.

The UE can detect a femtocell sync signal by detecting a synchronization signal of the femtocell at a predetermined offset from the synchronization signal of the macrocell, thereby determining whether the femtocell exists. Generally, a femtocell is downlink synchronized with a macrocell through a radio interface, a global positioning system (GPS), and the like. Since the downlink synchronization between the macrocell and the femtocell is matched, the UE can accurately detect the synchronization signal of the femtocell located at a predetermined offset from the synchronization signal of the macrocell.

In the case where the macrocell ID and the femtocell ID are transmitted at the same time and at the same time, when the terminal receives the information on the macrocell at the cell edge, it may be difficult to measure the received signal strength indication (RSSI) by the adjacent femtocell have. If the synchronization signal of the macrocell and the synchronization signal of the femtocell are transmitted at different times with predetermined offsets as in the proposed method, interference can be minimized in acquiring information on the adjacent macrocell and femtocell at the edge of the cell.

FIG. 5 illustrates a method of transmitting a macrocell ID and a femtocell ID according to another embodiment of the present invention.

Referring to FIG. 5, a macrocell ID and a femtocell ID may be used in different sequences, and a synchronization channel of a femtocell may be allocated to an offset position defined in a synchronization channel of a macrocell. That is, the synchronization signal of the macrocell and the synchronization signal of the femtocell can be transmitted in different signals with offsets in the time domain. At this time, the femtocells belonging to the femtocell group can use the same ID. That is, although the femtocell ID is different from the macrocell ID, femtocells belonging to the same femtocell group can use the same femtocell ID.

Since the macrocell ID and the femtocell ID are used in different sequences, the synchronization signal of the macrocell and the synchronization signal of the femtocell can be transmitted at the same position. However, interference between the macrocell ID and the femtocell ID, There is a problem of. For example, when the offset value of the sync signal of the macrocell and the femtocell is 0, two sync signals can be simultaneously transmitted. In this case, the UE does not need to receive two synchronization signals according to the synchronization signal cycle of the macrocell and the synchronization signal cycle of the femtocell, and can easily grasp the relative size of the synchronization signal strength of the macrocell and the synchronization signal strength of the femtocell . However, it is difficult to design a synchronization channel compared to the case where the offset value of the sync signal of the macrocell and the femtocell is not zero. For example, a part of the sequence used as the macrocell ID should be used as the femtocell ID, or a sequence of the femtocell ID with less interference should be used as the sequence of the macrocell ID. Accordingly, interference between the macrocell ID and the femtocell ID and the limitation of the cell ID may occur.

As shown in the figure, if the macrocell ID and the femtocell ID are transmitted using different sequences and different offset values, interference between the macrocell ID and the femtocell ID or restriction of the sequence can be solved. And a new type of sequence can be used without considering the interference with the existing macro cell ID with the femtocell ID. The terminal can accurately detect the femtocell ID at a predetermined offset position. In addition, even when a plurality of femtocells are adjacent to each other, the femtocell may apply different offset values to each femtocell to distinguish cell IDs among femtocells. That is, the offset value itself may be additional cell information. The offset value may be transmitted via a sync signal or broadcast information of the macrocell or femtocell.

The sequence used as the cell ID may be predefined as a sequence for a macrocell and a sequence for a femtocell. Therefore, even when the UE receives the initial synchronization signal from the femtocell cell area, it can know that the UE is within the cell area of the femtocell according to the predefined femtocell ID. If the sequence for the macrocell ID and the femtocell ID is not separately defined, the cell type of the macrocell and the femtocell can be transmitted through the broadcast information.

As described above, when the synchronization signal of the macrocell and the synchronization signal of the femtocell are transmitted without being offset, an additional sequence for distinguishing the macrocell ID and the femtocell ID is required. Accordingly, The complexity may increase and inter-cell interference may increase. In addition, there is a limitation on the IDs that can be used by the macrocell and the femtocell, and there may be restrictions on the installation of the femtocell due to the restriction of the femtocell ID that can be given in an environment where the femtocell is dense.

On the other hand, when the synchronization signal of the macrocell and the synchronization signal of the femtocell have offsets, it may be difficult for the terminal to find the synchronization signal of the femtocell. For example, when a mobile station is handing over from a macrocell to a femtocell in a state where a macrocell and a femtocell are synchronized with each other, the synchronization signal of the femtocell can be received from the synchronization signal of the macrocell. However, in a system environment in which there is no macrocell and only a femtocell is present, since there is no offset criterion, it may be difficult for the terminal to receive the synchronization signal of the femtocell. When the synchronization signal of the femtocell uses the same waveform as the synchronization signal of the macrocell, the terminal accesses the femtocell and then notifies that the corresponding cell is a femtocell through the broadcast information. When the synchronization signal of the femtocell uses a different waveform from the synchronization signal of the macrocell, the terminal may incur additional overhead for recognizing the synchronization signal waveform of the femtocell.

6 illustrates a method of transmitting a macrocell ID and a femtocell ID according to another embodiment of the present invention.

Referring to FIG. 6, the synchronization signal of the femtocell includes a primary synchronization signal and a secondary synchronization signal. The channel through which the main synchronization signal is transmitted is referred to as a main synchronization channel, and the channel through which the auxiliary synchronization signal is transmitted is referred to as an auxiliary synchronization channel. The main synchronization signal can be transmitted simultaneously with the synchronization signal of the macrocell. The auxiliary synchronization signal can be transmitted with a constant offset from the main synchronization signal or the synchronization signal of the macrocell. That is, the primary synchronization channel is allocated to a position where offset is 0 in the synchronization channel of the macrocell, and the secondary synchronization channel can be allocated to a position of offset greater than 0 in the synchronization channel of the macrocell.

The primary synchronization signal may include the same femtocell ID as the macrocell ID. Alternatively, the main synchronization signal may include an ID of a femtocell group including at least one femtocell. The auxiliary synchronization signal may include another femtocell ID for distinguishing the femtocells. That is, the first femtocell ID transmitted through the primary synchronization signal identifies the macrocell or the femtocell group, and the second femtocell ID transmitted through the secondary synchronization signal distinguishes the specific femtocell. Therefore, the actual ID of the femtocell is determined as the combination of the first femtocell ID through the main synchronization signal and the second femtocell ID through the auxiliary synchronization signal. The sequence of the main sync signal and the auxiliary sync signal may use the same type of sequence or different types of sequences. The main synchronization signal may be a sequence orthogonal to the sequence of the synchronization signal of the macrocell, and the auxiliary synchronization signal may use another sequence regardless of whether the synchronization signal is orthogonal to the sequence of the synchronization signal of the macrocell. In addition, the offset value between the main synchronization signal and the auxiliary synchronization signal can be determined for each femtocell, and thereby, additional cell information can be represented.

Since the main synchronization signal includes the same femtocell ID as the macrocell ID, the terminal can access the system according to the received synchronization signal without discriminating between the macrocell and the femtocell. The terminal can distinguish whether the system to which it is connected is a macro cell or a femtocell depending on whether the auxiliary synchronization signal is received or not, and can identify a specific femtocell by detecting an auxiliary synchronization signal. The UE can perform the handover between the femtocell and the femtocell through the auxiliary synchronization signal and the handover between the macrocell and the femtocell through the main synchronization signal.

Since femtocell supports a smaller number of terminals than a macrocell, it can use radio resources more than a macrocell. Accordingly, the femtocell can transmit the femtocell ID more efficiently without affecting the macrocell by providing the main synchronization channel and the auxiliary synchronization channel. That is, since the two femtocell IDs are transmitted to transmit two synchronization signals, the overhead increases. However, since the first femtocell ID is transmitted so as to be compatible with the macrocell ID, the second femtocell ID does not affect the macrocell, Ensure that femtocell IDs are correctly identified in non-existent system environments.

FIG. 7 illustrates a method for a terminal to process hierarchical cell information according to an embodiment of the present invention.

Referring to FIG. 7, the terminal receives a synchronization signal (S110). If the sequence for the macrocell ID and the sequence for the femtocell ID are predefined, the UE can decode the received synchronization signal to determine whether the synchronization signal is a macrocell or a femtocell synchronization signal.

The terminal detects another synchronizing signal during the period of the synchronizing signal (S120). Generally, the period of the synchronization signal is fixed according to the system, or the base station informs the terminal of the period of the synchronization signal through the system information. The terminal searches whether or not another synchronization signal is detected during a period of a predetermined synchronization signal. If another synchronous signal is detected during the period of the synchronous signal, it can be seen that the terminal is located in the hierarchical cell structure system environment. The synchronization signal of the femtocell may be received after a predetermined offset after the synchronization signal of the macrocell is received. The UE can acquire the macrocell ID from the synchronization signal of the macrocell and obtain the femtocell ID from the synchronization signal of the femtocell. Or a second femtocell ID after a predetermined offset after receiving the first femtocell ID. Accordingly, since the UE receives the cell information of the macrocell and the cell information of the femtocell during a period of one synchronization signal according to a predetermined offset, the UE can efficiently receive the cell information without interference between the macrocell and the femtocell.

The UE can determine a handover based on the received cell ID and the femtocell ID (S130).

All of the functions described above may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), etc. according to software or program code or the like coded to perform the function. The design, development and implementation of the above code will be apparent to those skilled in the art based on the description of the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. You will understand. Therefore, it is intended that the present invention covers all embodiments falling within the scope of the following claims, rather than being limited to the above-described embodiments.

1 is a block diagram illustrating a wireless communication system.

Fig. 2 shows an example of a frame structure.

3 shows another example of the frame structure.

FIG. 4 illustrates a method of transmitting a macrocell ID and a femtocell ID according to an embodiment of the present invention.

FIG. 5 illustrates a method of transmitting a macrocell ID and a femtocell ID according to another embodiment of the present invention.

6 illustrates a method of transmitting a macrocell ID and a femtocell ID according to another embodiment of the present invention.

FIG. 7 illustrates a method for a terminal to process hierarchical cell information according to an embodiment of the present invention.

Claims (8)

1. A method for processing hierarchical cell information in a wireless communication system having a hierarchical cell structure in which a small range of cells are overlapped in a wide range of cells, The method comprising: receiving a first synchronization signal including a cell identifier; And Wherein the period of the first synchronization signal is fixed and the second synchronization signal is detected during a period of the first synchronization signal, wherein the second synchronization signal is generated after the first synchronization signal is transmitted Wherein the cell ID included in the first synchronization signal is an ID of the wide range cell and the second synchronization signal is a synchronization signal transmitted from the cell of the small range, A method for processing red cell information. 2. The method of claim 1, wherein the second synchronization signal includes an ID of the cell in the small range. 3. The method of claim 2, wherein the cell ID included in the second synchronization signal is the same as the cell ID included in the first synchronization signal. 3. The method of claim 2, wherein the cell ID included in the second synchronization signal is different from the cell ID included in the first synchronization signal. The method of claim 1, wherein the period of the second synchronization signal is equal to the period of the first synchronization signal. 2. The wireless communication system according to claim 1, wherein the first synchronization signal is transmitted from the cell of the small range and the cell ID included in the first synchronization signal represents the group ID of the cell of the small range. A method for processing red cell information. The method of claim 1, wherein the offset information is transmitted through the first synchronization signal. The method of claim 1, wherein the offset information is transmitted through broadcast information.

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