KR101549019B1 - Power saving method of Femto base station through sleep cycle synchronization - Google Patents

Abstract

The present invention relates to a wireless access system, and more particularly, to a method for power saving in a femto base station. According to an embodiment of the present invention, there is provided a method of synchronizing a femto base station, comprising: acquiring reference synchronization information shared by another femto base station located in a predetermined area including a femto base station; And transitioning to a sleep mode in synchronization.

Therefore, power consumption of the femto base station and interference with the macro cell can be minimized in a wireless access system supporting the pamphlet, and the terminal in the pampho cell can perform reliable communication.

Femto base station, sleep mode, sleep mode information

Description

TECHNICAL FIELD [0001] The present invention relates to a power saving method for a femto base station through a sleep cycle synchronization,

The present invention relates to a wireless access system, and more particularly, to a method for power saving in a femto base station.

Hereinafter, the Femto Cell will be briefly described.

Femto refers to a very small unit of 10-15. In this sense, PAM TOCEL stands for indoor / outdoor office / home office / office. Pam tocels are used in a similar way to picocells, but they are used in a more evolved sense. PamTocell is a small cellular base station that connects to a broadband router. It can connect voice and data of 3G system as well as existing 2G system to mobile backbone network through DSL link.

The advantages of this pam toe cell are as follows.

Recently, PamTocell is promoting 3G distribution and it can become a catalyst for expanding indoor coverage. By 2011, the number of worldwide pam-toll cell users will increase to 120 million, and the number of AP (Access Point) base stations will reach 32 million. "Technically, enhanced indoor coverage of technologies such as W-CDMA, HSDPA, and EVDO are critical to service delivery," said Stuart Carlow, senior analyst at ABI Research. "PamTocell routes traffic through an IP network, which greatly enhances network quality and capacity," said Stuart Carlowe, "as well as the OPEX that mobile operators invest in backhaul lines, which is a huge benefit from both a strategic and economic point of view. "He said.

PAM tocels can enhance cell coverage and improve the quality of voice services. In addition, mobile operators expect to be able to fully adapt 3G to subscribers by providing data services via pam-cell. The pam toe cell may be referred to as a Femto Base Station (FBS) or a Femto BTS (Base Transceiver Station).

In summary, PAM TOCEL has the following advantages.

1. Cell Coverage Improvement

2. Infrastructure cost decrease

3. New service Offering

4. Fixed Mobile Convergence (FMC) acceleration

One or more PAM tokens may be grouped by specific service or region to form a Femtocell Group. For example, a pam cell group to which only a specific terminal is allowed to access may be referred to as a closed subscriber group (CSG). The femto base station (FBS) can confirm the CSG ID (CSG ID) of the terminal and permit the connection only to the terminal subscribed to the CSG.

1 is a diagram showing an example of a network structure including a femto base station (FBS).

Femto base stations are new additions to existing networks. Accordingly, as the use of the femto base station, there are matters to be added or changed in the overall network structure. The femto base station can directly access the Internet and perform a function as a base station. Thus, the femto base station can perform almost all the functions of a general macro base station. In addition, the femto base station may receive the data from the general macro base station and relay the data to the terminal.

FIG. 1 shows a form in which a Femto Network Gateway (FNG) is added to an existing network structure. The FNG can communicate with an Access Service Network (ASN) gateway and a Connectivity Service Network (CSN). The FNG may use the Rx interface for communication with the ASN and the Ry interface for communication with the CSN.

The femto base station can directly access the TCP / IP Internet network and receive service from the CSN through the FNG. A terminal connected to a femto base station can receive services such as authentication and IMS (IP Multimedia Subsystem) from an FNG or a CSN.

The femto base station is connected to the base station via the R1 interface. This indicates that the femto base station can receive a downlink (DL) channel of the macro base station. In addition, the femto base station can transmit the control signal to the macro base station.

In a commonly used broadband wireless access system, power consumption of a macro base station (Macro BS) is not considered. However, in an environment supporting pam-to-cell, a single pam-to-cell has a limited number of terminals supporting the service (approximately 5 to 6 terminals). Also, in some cases, the pamTocell may not have a terminal maintaining a connection for a certain time.

If such a situation is repeated, power consumption may occur as the pam toe cell continuously provides service even when it is not necessary to provide service to a specific terminal. In addition, if nearby femto base stations use the same frequency band in the femto system, interference may occur between nearby femto base stations.

Therefore, a way to overcome this situation is necessary.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for minimizing power consumption of a pamphlet in a wireless access system supporting a pamphlet.

It is another object of the present invention to provide a method for minimizing power consumption and interference with a macro cell when a terminal connected to the pam token does not exist or a terminal establishing a connection transits to an idle mode .

Another object of the present invention is to enable a terminal to perform reliable communication when the pam token is in a power saving mode.

It is another object of the present invention to provide a method for facilitating scanning of a femto base station of a terminal by matching operation cycles for power saving of all femtocells or similar femtocells existing in a predetermined area.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, unless further departing from the spirit and scope of the invention as defined by the appended claims. It will be possible.

In order to solve the above problems, the present invention discloses various methods for minimizing power consumption of a femto base station.

In one aspect of the present invention, there is provided a method of conserving power at a femto base station, comprising: acquiring reference synchronization information used in a predetermined area for a first femto base station to perform a sleep mode operation; Wherein the first femto base station is synchronized with at least one second femto base station belonging to the predetermined area using the reference synchronization information, Each femto base station may be synchronized with the sleep mode operation using the reference synchronization information.

Preferably, the reference synchronization information includes a sleep cycle, a listening interval, and an absolute or relative start frame number, wherein the reference synchronization information includes a transition to a sleep mode in synchronization with the reference synchronization information, May be performed to transition to the sleep mode to satisfy the sleep period, the listening interval, and the absolute or relative start frame.

Preferably, the reference synchronization information is set to have a predetermined listening interval and a sleep interval based on a predetermined start time point.

Preferably, the reference synchronization information may follow a listening interval and a sleeping period set by a femto base station transited to the sleep mode first among the first femto base station and the at least one second fermion base station.

Preferably, the sleep interval may be divided into an available interval and an unavailable interval.

Preferably, the sleep period may be one in which the possible interval and the incapable interval are started first.

Preferably, the step of synchronizing includes synchronizing a frame starting from a frame in which a new sleep cycle of the reference synchronization information that is the earliest from when the terminal is not present in the first femto base station starts .

Preferably, the first femto base station broadcasts at least one of a sync channel and a superframe header (SFH) only in the possible period in the sleep mode, and does not transmit / receive any data wirelessly in the disable period.

Advantageously, said synchronization channel is synchronized to said first femto base station and said at least one second femto base station.

Preferably, the method further comprises transmitting sleep mode information to the terminal, wherein the sleep mode information includes at least one of a start frame of a sleep mode according to the reference synchronization information, a sleep cycle, And a listening interval. ≪ Desc / Clms Page number 7 >

Preferably, the sleep mode information includes at least one of a superframe header (SFH), additional system information, a ranging response (RNG-RSP) message, a neighbor announcement (NBR-ADV) And an indication (FCB-LDM-IND) message.

Here, the neighbor announcement message and the femtocell base station low load mode indication (FCB-LDM-IND) message may be unicast or broadcast.

In addition, the predetermined area may be a macro cell area.

In addition, the reference synchronization information may exist more than two depending on the subscriber group type of the femtocell located in the predetermined area.

According to another aspect of the present invention, there is provided a method of saving power of a femto base station in a terminal, comprising: receiving a superframe header (SFH) and a synchronization channel from a first femto base station entering a sleep mode in synchronization with reference synchronization information used in a predetermined area Detecting a cell identifier and a CSG identifier of the first femto base station by decoding at least one of the superframe header (SFH) and the synchronization channel, detecting a cell identifier of the first femto base station and a CSG identifier of the first femto base station, And performing a connection to the first femto base station, wherein each of the femto base stations included in the predetermined area is synchronized with the sleep mode operation using the reference synchronization information.

Advantageously, the reference synchronization information may comprise a sleep cycle, a listening interval and an absolute or relative start frame number.

Advantageously, performing the connection to the first femto base station comprises receiving sleep mode information from the first femto base station or the macro base station and using the received sleep mode information to transmit the first Determining a sleep mode operation time point of the femto base station and transmitting a predetermined code or message to the first femto base station.

Preferably, the sleep mode information includes at least one of a start frame, a sleep cycle, and a listening interval of the sleep mode according to the reference synchronization information, The message may be transmitted to the first femto base station through a predetermined uplink resource of an available interval in the sleep period.

Preferably, when the terminal performs a connection to any one of the at least one second femto base stations, the terminal determines a sleep state of the first femto base station using the received sleep mode information Mode operation time point.

According to another aspect of the present invention, there is provided a method of conserving power in a femto base station, comprising: obtaining paging information of at least one terminal transiting to an idle mode in the femto base station; When the mobile terminal enters the idle mode, transitioning to the sleep mode considering paging information of the acquired at least one terminal.

Preferably, the paging information includes at least one of a paging cycle, a paging offset, and a paging listening interval. The paging cycle includes a paging listening interval, And a paging unavailable interval. The step of transitioning to the sleep mode may be performed when the at least one terminal in the femto base station satisfies a condition that the paging listening disabled period is more satisfied.

Preferably, the method further comprises a transition to a normal mode when any one of the at least one terminals in the femto base station is not the incommunicable period.

Preferably, the femto base station shares reference synchronization information with one or more other femto base stations located in a predetermined area to which the femto base station belongs,

The transition to the sleep mode may be performed in synchronization with the shared reference synchronization information.

According to the embodiments of the present invention, the following effects are obtained.

First, by using embodiments of the present invention, it is possible to minimize power consumption and interference with macrocells of a femto base station in a wireless access system supporting a pamphlet.

Second, by using the embodiments of the present invention, even if the femto base station operates in the power saving mode, the terminals in the pamphlet can perform reliable communication.

Third, by using the embodiments of the present invention, the terminal can more efficiently scan an entire femto base station or a homogeneous femto base station existing in a predetermined area.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

The present invention relates to a wireless access system. Embodiments of the present invention disclose various methods for minimizing power consumption of a femto base station.

The following embodiments are a combination of elements and features of the present invention in a predetermined form. Each component or characteristic may be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, some of the elements and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

In the description of the drawings, there is no description of procedures or steps that may obscure the gist of the present invention, nor is any description of steps or steps that can be understood by those skilled in the art.

Herein, embodiments of the present invention have been described with reference to a data transmission / reception relationship between a base station and a terminal. Herein, the base station is a terminal node of a network that directly communicates with the terminal. The specific operation described herein as performed by the base station may be performed by an upper node of the base station, as the case may be.

That is, various operations performed for communication with a terminal in a network consisting of a plurality of network nodes including a base station can be performed by a base station or other network nodes other than the base station. At this time, the 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. In addition, 'Mobile Station (MS)' may be replaced with terms such as User Equipment (UE), Subscriber Station (SS), Mobile Subscriber Station (MSS) or Mobile Terminal.

Also, the transmitting end refers to a node that transmits data or voice service, and the receiving end refers to a node that receives data or voice service. Therefore, in the uplink, the terminal may be the transmitting end and the base station may be the receiving end. Similarly, in the downlink, the terminal may be the receiving end and the base station may be the transmitting end.

Meanwhile, the mobile terminal of the present invention may be a PDA (Personal Digital Assistant), a cellular phone, a PCS (Personal Communication Service) phone, a GSM (Global System for Mobile) phone, a WCDMA (Wideband CDMA) Etc. may be used.

Embodiments of the present invention may be implemented by various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

For a hardware implementation, the method according to embodiments of the present invention may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs) , Field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to embodiments of the present invention may be implemented in the form of a module, a procedure or a function for performing the functions or operations described above. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the IEEE 802 systems, 3GPP systems, 3GPP LTE systems and 3GPP2 systems, which are wireless access systems. That is, the steps or portions of the embodiments of the present invention that are not described in order to clearly illustrate the technical idea of the present invention can be supported by the documents. In addition, all terms disclosed in this document may be described by the standard document. In particular, embodiments of the present invention may be supported by one or more of the documents P802.16-2004, P802.16e-2005 and P802.16Rev2, which are standard documents of the IEEE 802.16 system.

The specific terminology used in the following description is provided to aid understanding of the present invention, and the use of such specific terminology may be changed into other forms without departing from the technical idea of the present invention.

First Embodiment

The first embodiment of the present invention provides a method of saving power by entering a sleep mode in synchronization with other femto base stations in a predetermined area in the femto base station.

In this embodiment, it is assumed that the synchronization channel transmitted by the femto base station is synchronized with one or more other femto base stations located in a predetermined area to which the synchronization channel belongs. At this time, the predetermined area to which the femto base station belongs may be a whole network, a coverage area of at least one macro base station (MBS), a macro cell, or an area corresponding to at least one paging group have. It is also assumed that all the femto base stations appearing in the present embodiment exist in the predetermined area.

First, the femto base station can determine whether the sleep mode transition condition is satisfied in order to transition to the sleep mode. This will be described with reference to FIG.

2 is a state diagram showing a change in the power mode of the femto base station according to the first embodiment of the present invention.

Referring to FIG. 2, the femto base station can have two states. One operating in the normal mode and the other operating in the sleep mode. The sleep mode is a mode in which the femto base station broadcasts at least one of synchronization information (for example, P-SCH, S-SCH) and superframe header (SFH) Thereby reducing power consumption. Here, the sleep mode may be referred to as a low-duty mode.

The state of the femto base station transits from one state to another state when a certain condition is satisfied. For example, the femto base station may operate a predetermined count, and the predetermined count may be determined by the number of terminals subscribed to the CSG of the femto base station. That is, when the number of terminals subscribed to the CSG is n and the count value is 'n', it means that all terminals subscribed to the CSG are in the cell area of the femto base station. If the counter value is '0', it means that all the terminals that have subscribed to the CSG of the femto base station are out of the cell area of the femto base station or all of the terminals enter the idle mode or the sleep mode .

That is, when the count value is '0' or 'n' in FIG. 2, the femto base station can transition from the normal mode to the power saving mode (sleep mode or low duty mode). Thus, the femto base station can broadcast only the minimum signals transmitted to the terminals in the power saving mode, and the remaining operations can be stopped to minimize the power consumed by the femto base station.

However, in this embodiment, since the paging cycle of the UE transiting to the idle mode is not considered, it is preferable that the specific condition that the femto base station transits to the sleep mode is a case where no terminal exists in the femto base station.

Next, a sleep mode (Low Duty Mode) in which the femto base station can transit when the sleep mode transition condition is satisfied will be described with reference to FIG.

FIG. 3 shows a sleep cycle of a femto base station, which is periodically operated to reduce power consumption and interference on the air interface proposed by the first embodiment of the present invention.

Referring to FIG. 3, a sleep cycle of a femto base station may be configured as an available interval and an unavailable interval, and the role played by the femto base station in each interval is as follows.

First of all, the femto base station can transmit a synchronization channel and / or a superframe header (SFH) to the UEs in the downlink for a possible interval. Also, the femto base station can monitor whether there is a connection attempt transmitted by the terminal during a predetermined uplink interval, for example, ranging code transmission.

Next, the femto base station may block the uplink and the downlink during an idle period and may not transmit or receive any information over the radio. Thus, the femto base station can mitigate interference with neighboring femto base stations or macro base stations using the same frequency band, and at the same time can reduce power consumption.

The femto base station may start a possible interval in a sleep interval composed of such a possible interval and an impossible interval, or may start an invalid interval first.

However, in order for the femto base station to enter the sleep mode in synchronization with other femto base stations, a synchronization criterion is required. Here, the entry into the sleep mode synchronously means that all the femto base stations transiting to the sleep mode within a predetermined area repeat the sleep period of the same length at the same time. In other words, at the time when any femto base station operating in the sleep mode is enabled, all other femto base stations in a predetermined area operating in the sleep mode are possible intervals, and vice versa.

Thus, we propose a criterion that includes a sleep cycle, a listening interval and an absolute or relative start frame number for all femto base stations to operate in synchronized sleep mode. This is referred to herein as "reference synchronization information" or "low duty pattern ".

The reference synchronization information may be a repeated sleep cycle having a predetermined interval and an incapable interval based on a predetermined time point regardless of whether the sleep mode transition of all the femto base stations is performed. This can be determined by at least one of a macro base station, a paging controller, and a femto base station, which are responsible for a predetermined area.

Alternatively, the reference synchronization information may be a sleep cycle including a possible interval and an impossible interval set by the femto base station transited to the sleep mode first among the femto base stations. In this case, the sleep cycle set by the femto base station transited to the sleep mode for the first time may be continuously maintained as the reference synchronization information, or may be reset when there is no femto base station operating in the sleep mode, The sleep cycle of an arbitrary femto base station transited to the base station may be determined as new reference synchronization information.

The reference synchronization information determined by the above-described method may be maintained by at least one of a macro base station, a femto base station and a paging controller responsible for a predetermined area, and may be a predetermined Message to other femto base stations.

First, referring to FIG. 4, a case where the femto base station transitions to the sleep mode in accordance with the reference sleep time set regardless of the sleep mode transition of other femto base stations will be described. FIG. 4 shows an example of the operation of the femto base station transiting to the sleep mode in synchronization with the reference synchronization information according to the first embodiment of the present invention.

Referring to FIG. 4, it can be seen that the reference synchronization information to be repeated in a predetermined sleep cycle is set regardless of the sleep mode transition of the other femto base stations. The femto base station (Femto BS # 1) can acquire the reference synchronization information from at least one of the macro base station, the other femto base stations, and the paging controller (S401).

If the terminal does not exist in the femto base station, the femto base station can satisfy the condition for entering the sleep mode related to the present invention (S402).

The femto base station may transit to the sleep mode in accordance with the reference synchronization information immediately when the terminal does not exist, or may start a new sleep cycle of the reference synchronization information that comes first when the terminal is not present in the femto base station (S403). ≪ / RTI >

The femto BS entering the sleep mode through the above process can perform the sleep mode by repeating the possible interval and the impossible interval according to the reference synchronization information until the terminal attempts to access the coverage area of its own.

Next, a case where the sleep period set by the femto base station transited to the sleep mode for the first time is set as the reference synchronization information will be described with reference to FIG. 5 shows another example of the operation of the femto base station transiting to the sleep mode in synchronization with the reference synchronization information according to the first embodiment of the present invention.

5, assuming that no femto base station has transitioned to the sleep mode and there is no preset reference synchronization information, one femto BS # 2 may enter the sleep mode for the first time (S501).

At this time, the sleep period set by the femto BS # 2 transited to the sleep mode for the first time can be continuously set as the reference synchronization information, and the other femto BS # 1 can acquire the information about the reference synchronization information (S502).

Thereafter, when there is no terminal in the coverage area of the femto BS # 1, the femto BS # 1 can enter the sleep mode (S503).

At this time, the femto BS # 1 may transit to the sleep mode in accordance with the reference synchronization information, or may generate a new sleep cycle of the reference synchronization information that comes first from when the terminal is not present in its coverage area (Step S504). In this case, as shown in FIG.

A procedure in which a terminal attempts to access a femto base station transited to the sleep mode by the above-described method will be described with reference to FIG. 6 shows an example of the operation of the terminal and the femto base station according to the first embodiment of the present invention. In FIG. 6, it is assumed that the reference synchronization information is set in advance and shared by all the femto base stations in the predetermined area, and is maintained continuously.

Referring to FIG. 6, when the terminal enters the network of the femto base station, the sleep mode information can be obtained from the femto base station (S601). Herein, the sleep mode information refers to information that can be transmitted to the terminal so that the femto base station knows what type of sleep mode it operates. The sleep mode information may also be referred to as "Low Duty Pattern Information ".

The sleep mode information may include the following information.

1) Start frame: A frame number at the time when the fence base station transitions to the sleep mode. In the present invention, it may be a frame number at the start of a new sleep cycle of the basic sleep period.

2) Sleep Cycle: A period in which the femto base station operates in the sleep mode, and can be set in superframe units.

3) Listening interval: Indicates a possible interval of the interval in which the femto base station operates in the sleep mode. That is, during this interval, the femto base station transmits the synchronization channel information and the superframe header (SFH) to the terminal and monitors whether there is a ranging attempt transmitted by the terminal during the predetermined uplink interval.

When the sleep mode information is compared with the reference synchronization information, the sleep period and the listening interval of the sleep mode information may be the same as the sleep period and the listening interval of the reference synchronization information. However, the start frame of the sleep mode information may be different from the start frame of the reference synchronization information according to the time when the base station informs the terminal of the sleep mode information from the femto base station.

Such sleep mode information may be transmitted to the terminal through various methods. For example, the sleep mode information may be included in a ranging response (RNG-RSP) message when the terminal attempts initial entry or location update to the femto base station or the macro base station, have. For this, the ranging response message may include contents as shown in Table 1 below.

Syntax Size
(bit) Notes MOB_RNG-RSP_Message_format () { - - ~ Start Frame The frame number at the time when the femto base station transitions to the sleep mode Sleep Cycle The interval in which the femto base station operates in the sleep mode (SuperFrame unit) Listen Interval (LI) Indicates the available interval of the interval in which the femto base station operates in the sleep mode. That is, during this interval, the femto base station can transmit the synchronization information and the superframe header (SFH) to the terminals in the downlink, and also monitors whether there is a ranging attempt transmitted by the terminal during the predetermined uplink interval. ~ } // End of MOB_RNG-RSP

As another example, sleep mode information may be included in a super frame header (SFH) broadcast from a macro base station or a femto base station operating in a sleep mode, and may be transmitted to the terminal.

As another example, a method of transmitting sleep mode information to a terminal using additional system information will be described with reference to FIG.

FIG. 7 shows an example of a method in which a femto base station related to an embodiment of the present invention informs a sleep mode information to a terminal.

Referring to FIG. 7, a super frame header (SFH) may include a subframe number indicating the position of additional system information including sleep mode information in a corresponding superframe. The terminal can know the subframe number at which the sleep mode information is transmitted by decoding the super frame header (SFH), and can acquire the sleep mode information by checking the corresponding subframe. At this time, the additional system information may be DCD (Downlink Channel Discriptor).

As another example, sleep mode information may be included in a neighbor announcement (MOB_NBR-ADV) message transmitted from a macro base station or a femto base station and may be transmitted to a mobile station. The neighbor announcement message may be broadcast by the macro base station or the femto base station, or may be unicast through the unicast MOB_NBR-ADV message.

In addition, the sleep mode information may be included in a dedicated message, for example, a femtocell base station low load mode indication (FCB-LDM-IND) message to be transmitted to the terminal. The FCB-LDM-IND message can be unicast (unicast FCB-LDM-IND) or broadcast to the terminal from the macro base station or the femto base station.

6, the femto base station may enter the sleep mode according to the start frame included in the sleep mode information if the terminal does not exist in the curbside area (S602). Here, the time point indicated by the start frame may be a time point at which a new sleep cycle of the reference synchronization information starts. The femto base station which enters the sleep mode can perform the sleep mode by alternating the possible interval and the impossible interval in synchronization with the reference synchronization information.

Then, the terminal can acquire the information of the femto base station by decoding the synchronization channel (for example, P-SCH or S-SCH) transmitted by the femto base station. For example, the UE can time-synchronize with the base station by decoding the P-SCH. After the UE synchronizes the time, the UE can decode the S-SCH to acquire cell ID information. In addition, the UE may decode the P-SCH and the S-SCH and then decode the superframe header (SFH). The superframe header may include control information used in the base station.

However, in the embodiment of the present invention, if the P-SCH includes the identifier of the femto base station or the macro base station, or type information indicating whether the corresponding cell region is the pam cell region or the macro cell region, the terminal decodes the P- The control information can be obtained by decoding the super frame header.

If it is determined that the terminal having acquired the base station information and the synchronization information can access the femto base station through the above-described method, the femto base station in the power saving mode can be woken up by performing initial access (Initial Access) to the femto base station ). To this end, the MS can transmit an initial ranging code (Ranging Code) or a ranging request (RNG-REQ) message to the femto BS using the uplink resources preset in the sleep interval in the sleep period of the femto BS.

If there is an initial connection request from the terminal, the femto base station awakes in the sleep mode and can perform a normal mode operation (S604).

Thereafter, if the terminal does not exist in the network again, the femto base station can transition to the sleep mode in synchronization with the reference synchronization information (S605).

Next, referring to FIG. 8, a case in which an incapable period starts first in a sleep cycle of a basic sleeping period will be described.

FIG. 8 shows another example of the operation of the terminal and the femto base station according to the first embodiment of the present invention.

Referring to FIG. 8, the process of operating in the sleep mode of the femto base station is basically the same as that of FIG. 6, but it can be seen that the disabled period starts first in the sleep interval of the basic sleep interval, and then the possible interval is set. Descriptions of duplicate portions for simplicity of the description are omitted. If the discontinuity starts in the sleep interval as described above, it can be usefully applied when it is determined that the probability that another mobile station will not enter immediately after the mobile station has not existed in the coverage area of the femto base station is high.

On the other hand, as described above, all the femto base stations in the predetermined area perform the sleep mode operation in synchronization with the reference synchronization information. Accordingly, when the terminal acquires the sleep mode information once and grasps the sleep mode operation time of the femto base station, when the terminal attempts to access another femto base station operating in the sleep mode, It is efficient. Further, when the entire wireless communication network operates at the same frequency, there is an effect of reducing interference by matching the reference synchronization information of the femto base stations.

In the present embodiment, one reference synchronization information exists in a predetermined area. However, there may be two or more reference synchronization information.

For example, the femto base stations operating at the frequency of f1 may operate in the sleep mode in synchronization with different reference synchronization information from the femto base stations operating at the frequency of f2.

As another example, different types of reference synchronization information may be provided for different types of femto base stations located within a predetermined area. That is, the femto base stations to which the CSG is applied operate in the sleep mode according to the first reference synchronization information, and the femto BSs to which the open subscriber group (OSG) So that it can operate in the sleep mode. Among the femto base stations to which the CSG is applied, the femto base stations of the CSG-Closed type that do not provide any services to the terminals that are not subscribed to the CSG are classified into the CSG-Open type The femto base stations can operate in the sleep mode according to different reference synchronization information. At this time, the size of the predetermined area may be an area corresponding to the macro cell.

In this way, the femto base stations of the same type operate in the sleep mode according to the same reference synchronization information, thereby reducing the interference between the femto base stations. When the terminal acquires the sleep mode information once, The femtocell of FIG.

Second Embodiment

In another embodiment of the present invention, when all the terminals in the cell area of the femto base station are in the idle mode, the femto base station sets the paging cycle, the paging offset, and the paging listening interval Listening Interval) to operate in the sleep mode.

For example, the femto base station performs normal operation (16m superframe transmission) in a paging listening interval of the mobile station, i.e., a possible interval, and transmits a paging unavailable interval of the mobile station, Paging cycle) can transition to the sleep mode. Here, the sleep mode performed by the femto base station may be classified into a possible interval and an unavailable interval, and the operations performed in each interval are the same as those described in the first embodiment, so duplicate descriptions are omitted.

In order for the femto base station to operate in the power saving mode in accordance with the paging cycle of the terminals, if the paging cycle, the paging listening interval, the paging disable period, and the paging offset of all the terminals in the femtocell area are the same, And normal mode. However, when any one of the terminals in the coverage area of the femto base station has a different paging cycle, a power saving method for the femto base station is required. This will be described with reference to FIG.

9 illustrates a power saving method in which different paging periods of a plurality of terminals are considered in a femto base station related to the second embodiment of the present invention.

Referring to FIG. 9, it can be seen that there are three terminals (MS A, MS B, and MS C) in the coverage area of the femto base station and transition to the idle mode with different paging periods and paging offsets.

The femto base station can exchange a DREG-REQ message and a DREG-CMD message with each terminal when each terminal transits to the idle mode. In this process, Information about the paging offset and the paging listening interval can be obtained. Since all the terminals in the own area enter the idle mode, the user can transition to the sleep mode for power saving.

In this case, when the femto base station receives a paging notification indicating that there is a call or packet to be transmitted from the paging controller to at least one of the three terminals, the femto base station must notify the terminal through the paging message within the paging listening interval of the corresponding terminal. Therefore, it is preferable that the femto base station operates in the normal mode if any of the terminals existing in its coverage area is in the paging listening interval. On the contrary, the femto base station can operate in the sleep mode when all terminals are in the paging disabled period.

As a result, the femto base station can repeat the sleep mode and the normal mode until one of the three terminals transits to the normal mode as shown in FIG.

Also in this embodiment, as in the first embodiment, all the femto base stations in the predetermined area can repeat the possible section and the impossible section in the sleep mode in synchronization with the reference synchronization information. This will be described with reference to FIG.

FIG. 10 shows a power saving method in which reference synchronization information is further considered in the femto base station according to the second embodiment of the present invention.

Referring to FIG. 10, it can be seen that three terminals (MS A, MS B, and MS C) transit to idle mode with different paging periods and paging offsets in the network as shown in FIG. At this time, it is assumed that the preset reference sleep time is shared by all the femto base stations in the predetermined area.

The femto base station can repeat the sleep mode and the normal mode in the same manner as the method described in Fig. Herein, since the femto base station knows predetermined reference synchronization information, it is possible to save power by performing a sleep mode in synchronization with the reference synchronization information in repeating the possible interval and the impossible interval in the sleep mode.

When the terminal acquires the sleep mode information once and recognizes the sleep mode operation time of the femto base station, the terminal obtains the sleep mode information obtained when attempting to access another femto base station that exists in a predetermined area and operates in the sleep mode It is efficient because it can be reused without having to update.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention. In addition, claims that do not have an explicit citation in the claims can be combined to form an embodiment or included as a new claim by amendment after the application.

1 is a diagram showing an example of a network structure including a femto base station (FBS).

2 is a state diagram showing a change in the power mode of the femto base station according to the first embodiment of the present invention.

FIG. 3 shows a sleep cycle of a femto base station, which is periodically operated to reduce power consumption and reduce interference on an air interface, in the femto base station proposed in the first embodiment of the present invention.

FIG. 4 shows an example of the operation of the femto base station transiting to the sleep mode in synchronization with the reference synchronization information according to the first embodiment of the present invention.

5 shows another example of the operation of the femto base station transiting to the sleep mode in synchronization with the reference synchronization information according to the first embodiment of the present invention.

6 shows an example of the operation of the terminal and the femto base station according to the first embodiment of the present invention.

FIG. 7 shows an example of a method in which a femto base station related to an embodiment of the present invention informs a sleep mode information to a terminal.

FIG. 8 shows another example of the operation of the terminal and the femto base station according to the first embodiment of the present invention.

9 illustrates a power saving method in which different paging periods of a plurality of terminals are considered in a femto base station related to the second embodiment of the present invention.

FIG. 10 shows a power saving method in which reference synchronization information is further considered in the femto base station according to the second embodiment of the present invention.

Claims (20)

A method of performing a low duty mode operation in a femto base station, Transmitting information on the low load pattern parameters for the low load mode operation to the terminal through a unicast message when the terminal enters the network; Determining whether a predetermined condition for entering the low load mode operation is satisfied; And And entering the low load mode operation at a start timing according to low load pattern parameters for the low load mode operation if the predetermined condition is satisfied, Wherein the low load pattern parameters include information on an available interval and information on the start timing to start the low load mode operation, The length of the available interval and the length of the unavailable interval are each super frame units, Wherein the low load mode operation is repeatedly performed to activate the air interface in the available interval and to deactivate transmission on the air interface in the unavailable interval. The method according to claim 1, Wherein the predetermined condition is a condition in which there is no terminal attached to the femto base station. delete A method for performing communication with a femto base station in which a terminal supports a low duty mode operation, And receiving information on the low load pattern parameters for the low load mode operation through a unicast message upon network entry, The information on the low load pattern parameters includes information on an available interval and information on a start timing for starting the low load mode operation, The length of the usable interval and the length of the unavailable interval are each superframe units, Wherein the terminal repeatedly performs the operation of activating the wireless interface in the available interval and deactivating the transmission on the wireless interface in the unavailable interval so that communication with the femto base station supporting low load mode operation How to do it. 5. The method of claim 4, Wherein the low load mode operation is initiated when a terminal attached to the femto base station is not present. A femto base station performing a low duty mode operation, A transmitter for transmitting information on the low load pattern parameters for the low load mode operation to the terminal through a unicast message when the terminal enters the network; Determining whether a predetermined condition for entering the low load mode operation is satisfied; and if the predetermined condition is satisfied, changing the start timing to the low load mode operation according to the low load pattern parameters for the low load mode operation A processor for controlling to enter, Wherein the low load pattern parameters include information on an available interval and information on the start timing to start the low load mode operation, The length of the available interval and the length of the unavailable interval are each superframe, Wherein the processor controls to repeatedly perform an operation of activating an air interface in the available interval in the low load mode operation and of disabling transmission on the air interface in the unavailable interval. The method according to claim 6, Wherein the predetermined condition is a condition in which there is no terminal attached to the femto base station. 1. A terminal performing communication with a femto base station supporting a low duty mode operation, receiving set; And A processor, Wherein the receiver receives information on low load pattern parameters for the low load mode operation via a unicast message upon network entry, The information on the low load pattern parameters includes information on an available interval and information on a start timing for starting the low load mode operation, The length of the available interval and the length of the unavailable interval are each superframe, Wherein the processor controls to repeatedly perform an operation of activating a wireless interface in an interval in which the terminal is available and inactivating transmission in the unavailable interval. 9. The method of claim 8, Wherein the low load mode operation is initiated when a terminal attached to the femto base station does not exist. delete delete delete delete delete delete delete delete delete delete delete

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