WO2015080420A1

WO2015080420A1 - Device and method for discovering small cell in wireless communication system

Info

Publication number: WO2015080420A1
Application number: PCT/KR2014/011096
Authority: WO
Inventors: 정정수; 강현정; 권상욱; 권종형; 김석원; 류선희; 신봉진; 이성진
Original assignee: 삼성전자주식회사
Priority date: 2013-11-29
Filing date: 2014-11-19
Publication date: 2015-06-04

Abstract

The purpose of the present invention is to discover a small cell in a wireless communication system. An operation of a terminal in the wireless communication system comprises the steps of: receiving a first signal for informing of the existence of a small cell according to a first measurement cycle; and attempting to detect the first signal and a second signal for informing of the service coverage of the small cell according to a second measurement cycle after detecting the first signal. In addition, the present invention also comprises embodiments other than the embodiment described above.

Description

Apparatus and method for discovering small cells in a wireless communication system

The present invention relates to the discovery of small cells in a wireless communication system.

Wireless communication systems are rapidly evolving. In particular, recently, wireless communication systems are being developed to support high-speed, high-capacity data services to meet various needs of users. As one method for the high-speed, high-capacity data service, it is considered to install a small cell as well as a conventional macro cell.

In general, since the small cell has a narrow coverage, the small cell can support a higher data rate than the data rate serviced by the macro cell by a closer distance from the terminal. Therefore, when it is difficult to communicate with an existing macro cell, efficient network operation is possible by using the small cell supporting the high data rate. That is, the small cell may be used in a shadowed area of the macro cell or an area having high traffic demand, thereby contributing to effective network operation.

In order to access the small cell, the terminal must first discover the small cell. That is, since the small cell has narrower coverage than the macro cell, the terminal is more likely to initially access the macro cell. Accordingly, after the UE, which is connected to the macro cell, discovers the small cell, it may handover to the small cell. Thus, there is a need for procedures and techniques for finding the small cell more efficiently.

One embodiment of the present invention provides an apparatus and method for discovering a small cell in a wireless communication system.

Another embodiment of the present invention provides an apparatus and method for transmitting a signal for small cell discovery in a wireless communication system.

Another embodiment of the present invention provides an apparatus and method for adjusting a measurement period for discovering a small cell of a terminal in a wireless communication system.

In a wireless communication system according to an embodiment of the present invention, a method of operating a terminal includes: receiving a first signal indicating the presence of a small cell according to a first measurement period; and after detecting the first signal, performing a second measurement. And detecting a first signal and a second signal indicating a service coverage of the small cell according to a period.

In a method of operating a small cell base station in a wireless communication system according to another embodiment of the present invention, a process of periodically transmitting a first signal for notifying the existence of the small cell and a second for notifying service coverage of the small cell It characterized in that it comprises a process of transmitting a signal.

In a wireless communication system according to another embodiment of the present invention, a terminal device includes a transceiver for receiving a first signal indicating the presence of a small cell according to a first measurement period, the first signal and a second measurement period. And a control unit for attempting to detect a second signal informing of service coverage of the small cell.

In a wireless communication system according to another embodiment of the present invention, a small cell base station apparatus includes a transmitter for transmitting a signal through a wireless channel, a first signal for periodically notifying the presence of the small cell, and the small cell. And a control unit for controlling to transmit a second signal for notifying the service coverage of the service.

In a wireless communication system, a signal for discovery of a small cell may be composed of two signals, and the two signals may be transmitted to have different coverages, thereby optimizing a measurement operation of the terminal.

1 illustrates an example of relationships between a macro cell and a small cell in a wireless communication system according to an embodiment of the present invention.

2 illustrates a signal transmission for small cell discovery in a wireless communication system according to an embodiment of the present invention.

3 illustrates an example of a measurement operation for small cell discovery in a wireless communication system according to an embodiment of the present invention.

4 illustrates coverage of a discovery signal in a wireless communication system according to an embodiment of the present invention.

5 illustrates an example of a configuration of a discovery channel in a wireless communication system according to an embodiment of the present invention.

6 illustrates another configuration example of a discovery channel in a wireless communication system according to an embodiment of the present invention.

7 illustrates another configuration example of a discovery channel in a wireless communication system according to an embodiment of the present invention.

8 illustrates another configuration example of a discovery channel in a wireless communication system according to an embodiment of the present invention.

9 illustrates an example of operation of a discovery channel in a wireless communication system according to an embodiment of the present invention.

10 illustrates another operation example of a discovery channel in a wireless communication system according to an embodiment of the present invention.

11 illustrates an example of a measurement event result of a mobile terminal in a wireless communication system according to an exemplary embodiment of the present invention.

12 illustrates another example of a measurement event result of a mobile terminal in a wireless communication system according to an exemplary embodiment of the present invention.

13 illustrates another example of a measurement event result of a mobile terminal in a wireless communication system according to an exemplary embodiment of the present invention.

14 illustrates an example of movement paths of a terminal in a wireless communication system according to an embodiment of the present invention.

15 illustrates an operation procedure of a terminal in a wireless communication system according to an embodiment of the present invention.

16 is a flowchart illustrating an operation procedure of a macro base station in a wireless communication system according to an exemplary embodiment of the present invention.

17 illustrates an operation procedure of a small cell base station in a wireless communication system according to an embodiment of the present invention.

18 is a block diagram of a terminal in a wireless communication system according to an exemplary embodiment of the present invention.

19 is a block diagram of a base station in a wireless communication system according to an embodiment of the present invention.

With reference to the accompanying drawings will be described in detail the operating principle of the present invention. In the following description, detailed descriptions of well-known functions or configurations related to the present invention will be omitted when it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, the present invention describes a technique for discovering a small cell in a wireless communication system. In the following description, the 'small cell' may be used interchangeably to refer to a small cell base station providing a small cell and the coverage provided by the small cell base station. In addition, terms used for describing cells, frame structures, channels, signals, and the like used in the following description are for convenience of description. Accordingly, the invention is not limited to the terms described below, and other terms may be used to refer to objects having equivalent technical meanings.

Referring to FIG. 1, examples of four arrangements for the macro cell 110 and the small cell cluster 120 are introduced. The small cell cluster 120 refers to a group of a plurality of small cells. The four arrangements illustrated in FIG. 1 are classified according to the operating frequency and whether indoor / outdoor.

Referring to FIG. 1A, the macro cell 110 and the small cell cluster 120 may operate at the same frequency f1. In this case, the small cell cluster 120 is installed outdoors. In this case, the macro cell 110 and the small cell cluster 120 may interfere with each other. However, when the terminal wants to find a small cell, the terminal may measure at a frequency communicating with the macro cell 110.

Referring to FIG. 1B, the macro cell 110 may operate at a frequency f1, and the small cell cluster 120 may operate at a frequency f2. In this case, the small cell cluster 120 is installed outdoors. In this case, the macro cell 110 and the small cell cluster 120 do not interfere with each other. When the terminal wants to find a small cell, the terminal may measure after changing the operating frequency.

Referring to FIG. 1C, the macro cell 110 may operate at a frequency f1, and the small cell cluster 120 may operate at a frequency f2. At this time, the small cell cluster 120 is installed indoors. That is, the small cell cluster 120 covers the indoor shadow area. Since the frequency at which the macro cell 110 and the small cell cluster 120 operate are different, when the terminal wants to find the small cell, the terminal may measure the operating frequency after changing the operating frequency.

Referring to FIG. 1D, the macro cell 110 and the small cell cluster 120 may operate at the same frequency f1 or f2. At this time, the small cell cluster 120 is installed indoors. That is, the small cell cluster 120 covers the indoor shadow area. Since the frequency at which the macro cell 110 and the small cell cluster 120 operate is the same, when the terminal wants to discover the small cell, the terminal may measure at the frequency communicating with the macro cell 110. .

2 illustrates a signal transmission for small cell discovery in a wireless communication system according to an embodiment of the present invention. 2 illustrates transmitting signals for small cell discovery at two small cell base stations 221 and 222.

Referring to FIG. 2, the small cell base station # 1 221 and the small cell base station # 2 222 periodically transmit a small cell discovery signal. The channel for delivering the small cell discovery signal may be referred to as a 'discovery channel'. In this case, the small cell base station # 1 221 and the small cell base station # 2 222 perform cooperative muting. That is, when the small cell base station # 1 221 transmits the small cell discovery signal, the small cell base station # 2 222 does not transmit any signal for the transmission resource in the interval during the discovery channel period. On the contrary, when the small cell base station # 2 222 transmits the small cell discovery signal, the small cell base station # 1 221 does not transmit any signal for the transmission resource in the interval during the discovery channel period. To this end, frame synchronization between the small cell base station # 1 221 and the small cell base station # 2 222 may be required. Accordingly, the small cell discovery signal may be transmitted without interference by other signals, and may provide wider coverage than other signals (eg, data signals) in which interference exists.

The terminal 230 attempts to detect and measure the small cell discovery signal according to the scheduling information for the small cell discovery signal transmission of the small cell base station # 1 221 and the small cell base station # 2 222. . The scheduling information may be provided to the terminal 230 in various ways. For example, the scheduling information may be provided from the macro base station to the terminal 230. Upon successful detection of the small cell discovery signal, the terminal transmits a report 290 to the macro cell.

In the embodiment shown in FIG. 2, the base station # 1 221 and the base station # 2 222 transmit the discovery signals at different frames, that is, at different times. However, according to another embodiment of the present invention, the base station # 1 221 and the base station # 2 222 may transmit the discovery signals at the same frame, that is, at the same time. When the discovery signal transmission time points of the base station # 1 221 and the base station # 2 222 are the same, resources for the discovery signal transmission of the base station # 1 221 and the base station # 2 222 are exclusively In other words, they may be allocated to different time-frequency domains.

3 illustrates an example of a measurement operation for small cell discovery in a wireless communication system according to an embodiment of the present invention. 3 illustrates movement trajectories of the terminal.

Referring to FIG. 3, paths # 1 301 and # 2 302 are paths through a cell, where path # 1 301 is a slow movement, and paths # 2 302 are relatively High speed movement. The case where the detection attempt of the small cell discovery signal is performed periodically at a time interval of 200 ms is illustrated. In this case, according to the route # 1 301, twelve measurements are performed. Also, according to path # 2 302, three measurements are performed. In this case, when the small cell discovery signal is successfully detected by being located in the cell at the time of measurement, it is seven times in the route # 1 301 and one time in the route # 2 302.

The number of times the detection of the small cell discovery signal by the mobile terminal is performed is related to the coverage of the discovery channel. For example, as the coverage of the discovery channel is wider, the number of times the small cell discovery signal is detected may be increased. Since frequent performing of the detection operation causes a rapid consumption of power, there is a need to reduce the number of detections. To this end, a method of increasing the transmission period of the small cell discovery signal or performing a measurement less frequently in the terminal may be considered. However, in this case, the discovery and measurement performance of the small cell may be degraded. Accordingly, the present invention further proposes a structure of a discovery channel as shown in FIG. 4.

4 illustrates coverage of a discovery signal in a wireless communication system according to an embodiment of the present invention. The coverage illustrated in FIG. 4 may be defined based on a received strength of the discovery signal or a signal to interference and noise ratio (SINR) of the discovery signal.

Referring to FIG. 4, the discovery signal of the small cell base station 420 has two coverages 450 and 460. That is, the discovery signal includes at least two signals. Specifically, the discovery signal may be a first signal for notifying the existence of the small cell base station 420, a service coverage capable of data communication of the small cell base station 420, or a signal-to-interference and noise ratio corresponding to the coverage (SINR). ) A second signal for informing. Hereinafter, for convenience of description, the first signal is referred to as a 'detection signal 470' and the second signal is referred to as a 'coverage signal 480'.

According to an embodiment of the present invention, the coverage 460 of the detection signal 470 is designed and operated to be relatively wider than the coverage 450 of the coverage signal 480. For example, the coverage signal 480 may be operated to transmit all adjacent small cells together, and the detection signal 470 may be operated to transmit only some small cells. The terminal may independently detect the detection signal 470 and the coverage signal 480. Accordingly, the terminal first recognizes the existence of the small cell base station 420 through the detection signal 470, and the small cell base station (SINR) through the signal-to-interference and noise ratio (SINR) of the coverage signal 480. It may be determined whether or not communication with 420 is possible. Here, the signal-to-interference and noise ratio can be replaced by another metric indicating channel quality. For example, the signal-to-interference and noise ratio includes a signal-to-noise ratio (SNR), a carrier-to-interference and noise ratio (CINR), and the like. Further, the channel quality may be a combination of two or more of the signal to interference and noise ratio, the signal to noise ratio, the carrier to interference and noise ratio.

The detection signal 470 and the coverage signal 480 may be configured in a predefined sequence, such as a synchronization signal. Alternatively, the detection signal 470 and the coverage signal 480 occupy some tones of an Orthogonal Frequency Division Multiplexing (OFDM) symbol, such as a reference signal, and are transmitted together with data symbols. It may be configured to. As another example, one of the detection signal 470 and the coverage signal 480 may be configured as the synchronization signal, and the other may be configured as the reference signal. The detection signal 470 and the coverage signal 480 may include identification information of the small cell base station 420 and operation state (eg, active / dormant state information). In addition, the detection signal 470 and the coverage signal 480 may further include information necessary for communication with the small cell base station 420. A detailed configuration example of the detection signal 470 and the coverage signal 480 is as shown in FIGS. 5 to 8.

5 illustrates an example of a configuration of a discovery channel in a wireless communication system according to an embodiment of the present invention. Referring to FIG. 5, the detection signal 570 and the coverage signal 580 are transmitted in one frame or subframe. In FIG. 5, the detection signal 570 and the coverage signal 580 are multiplexed on the time axis. In other words, in FIG. 5, an area for the detection signal 570 and an area for the coverage signal 580 are defined in different time resources of the same frame or subframe. However, according to another embodiment of the present invention, the detection signal 570 and the coverage signal 580 may be multiplexed on the frequency axis. Alternatively, the detection signal 570 and the coverage signal 580 may be multiplexed in another manner.

6 illustrates another configuration example of a discovery channel in a wireless communication system according to an embodiment of the present invention. Referring to FIG. 6, a detection signal 670 is transmitted in some frames or some subframes and a coverage signal 680 is transmitted in the remaining frames or the remaining subframes. In other words, in the case of FIG. 6, each frame or each subframe includes one of the area for the detection signal 670 and the coverage signal 680.

7 illustrates another configuration example of a discovery channel in a wireless communication system according to an embodiment of the present invention. FIG. 7 illustrates a case where the detection signal 770 and the coverage signal 780 are configured together with the reference signal. Referring to FIG. 7, the detection signal 770 and the coverage signal 780 may be multiplexed on the frequency axis. That is, the detection signal 770 and the coverage signal 780 are mapped to some symbols among symbols in a slot, the detection signal 770 is mapped to some subcarriers, and the coverage is performed on the remaining subcarriers. Signal 780 is mapped.

8 illustrates another configuration example of a discovery channel in a wireless communication system according to an embodiment of the present invention. 8 illustrates a case where the detection signal 870 and the coverage signal 880 are configured together with a reference signal. Referring to FIG. 8, the detection signal 870 and the coverage signal 880 may be multiplexed based on an antenna port. That is, the detection signal 870 is mapped to tones for a specific antenna and the coverage signal 880 is mapped to tones for another antenna.

Operation of the discovery channel according to an embodiment of the present invention may be classified according to the operation state of the small cell. The operating state of the small cell may be divided into an active state and a dormant state. The active state refers to a state in which at least one terminal is connected to the small cell, and the small cell communicates. The dormant state refers to a situation in which a terminal connected to the small cell does not exist, and the small cell does not perform communication. Even in the dormant state, the small cell may transmit some of the signals transmitted in the active state.

The small cell transmits the detection signal regardless of the operation state, but may transmit the coverage signal according to the operation state. The detection signal is for informing the presence or absence of the corresponding small cell and needs to be transmitted regardless of the operation state. However, since the small cell's communicable coverage or signal-to-interference and noise ratio (SINR) corresponding to the coverage depends on the actual communication state, it is more advantageous for accurate coverage to know that the coverage signal is only transmitted in the active state. to be. However, since the operation state of the small cell may be changed, even the small cell in the dormant state may transmit the coverage signal on some discovery channels. For example, in the active state, the small cell may transmit a detection signal according to a predefined period, and transmit a coverage signal in the coverage signal region of all discovery channels. On the other hand, in the dormant state, the small cell may transmit the detection signal according to a predefined period, and may transmit the coverage signal together only when the detection signal is transmitted. Hereinafter, specific operations of the discovery channel will be described with reference to FIG. 9.

9 illustrates an example of operating a discovery channel in a wireless communication system according to an embodiment of the present invention. 9 illustrates a situation in which four small cells 921 to 924 are located adjacent to each other, wherein the small cell base station # 2 922 and the small cell base station # 4 924 are active, the small cell base station # 1 921 and A case where the small cell base station # 3 923 is in the dormant state is illustrated. In FIG. 9, the solid line indicates coverage of the coverage signal 980 and the dotted line means coverage of the detection signal 970.

Referring to FIG. 9, in frame # 1, the small cell base station # 1 921 transmits a detection signal 970. In the frame # 1, the small cell base station # 1 921, the small cell base station # 2 922, and the small cell base station # 4 924 transmit a coverage signal 980. The small cell base station # 2 922 and the small cell base station # 4 924 are active and transmit the coverage signal 980. The small cell base station # 1 921 transmits the coverage signal 980 together with the detection signal 970 since the dormant state or the transmission period of the detection signal 970 has arrived.

In frame # 2, the small cell base station # 2 922 transmits a detection signal 970. In the frame # 2, the small cell base station # 2 922 and the small cell base station # 4 924 transmit a coverage signal 980. The small cell base station # 2 922 and the small cell base station # 4 924 are active and transmit the coverage signal 980.

In frame # 3, the small cell base station # 3 923 transmits a detection signal 970. In the frame # 3, the small cell base station # 2 922, the small cell base station # 3 923, and the small cell base station # 4 924 transmit a coverage signal 980. The small cell base station # 2 922 and the small cell base station # 4 924 are active and transmit the coverage signal 980. The small cell base station # 3 923 transmits the coverage signal 980 together with the detection signal 970 since the dormant state or the transmission period of the detection signal 970 has arrived.

In frame # 4, the small cell base station # 4 924 transmits a detection signal 970. In the frame # 4, the small cell base station # 2 922 and the small cell base station # 4 924 transmit a coverage signal 980. The small cell base station # 2 922 and the small cell base station # 4 924 are active and transmit the coverage signal 980.

In the embodiment shown in FIG. 9, the detection signal 970 and the coverage signal 980 are multiplexed within one frame. However, according to another exemplary embodiment, the detection signal 970 and the coverage signal 980 may be multiplexed based on a frame or subframe. In this case, the frame transmitting the detection signal 970 and the frame transmitting the coverage signal 980 may be bundled in a pair and operated similarly to the method of FIG. 9.

In the embodiment shown in FIG. 9, the detection signal 970 and the coverage signal 980 are multiplexed on the time axis. However, according to another embodiment of the present invention, the detection signal 970 and the coverage signal 980 may be multiplexed in the frequency axis, or multiplexed in a domain of resources other than the time axis or the frequency axis.

In the example illustrated in FIG. 9, each of the base stations 1021 to 1024 transmits the discovery signals at different frames, that is, at different times. However, according to another embodiment of the present invention, the base station # 1 221 and the base station # 2 222 may transmit the discovery signals at the same frame, that is, at the same time. When the discovery signal transmission time points of the base station # 1 221 and the base station # 2 222 are the same, resources for the discovery signal transmission of the base station # 1 221 and the base station # 2 222 are exclusively In other words, they may be allocated to different time-frequency domains.

In the above-described embodiment, the coverage signal is transmitted to inform the communicable coverage of the small cell. Therefore, according to an embodiment of the present invention, the small cell may inform the load level through the coverage signal. The load indicates a ratio of resources in use, and for example, may be expressed by at least one of the number of connected terminals and the ratio of resources in use to all available resources.

For example, the small cell may inform the degree of load by partially punching the tones of the coverage signal. For example, the number of tones to be drilled may be higher at lower load levels. In other words, as the load level is higher, a larger number of tones may constitute the coverage signal. That is, as the load level is higher, more interference may be caused to adjacent cells, so that the number of punctured tones may be adjusted so that the interference due to the coverage signal reflects the interference during data transmission.

As a specific example, when the load level is 80% or more, all available tones may constitute the coverage signal. If the load level is between 30% and 80%, 50% of all available tones are punctured and the remaining 50% may constitute the coverage signal. If the load level is less than 30%, 70% of all available tones are punctured and the remaining 30% may constitute the coverage signal.

An example of operation of a discovery channel when the coverage signal is partially punctured is shown in FIG. 10. 10 illustrates another operation example of a discovery channel in a wireless communication system according to an embodiment of the present invention. FIG. 10 illustrates a situation in which four small cells 1021 to 1024 are adjacent to each other, wherein small cell base station # 2 1022 and small cell base station # 4 1024 are active, small cell base station # 1 1021, and A case where the small cell base station # 3 1023 is in the dormant state is illustrated. In FIG. 10, the solid line indicates coverage of the coverage signal 1080, and the dotted line means coverage of the detection signal 1070. In FIG. 10, the frequency axis width of the coverage signal 1080 represents the number of tones constituting the coverage signal 1080, that is, the tones that are not punctured.

Referring to FIG. 10, in frame # 1, the small cell base station # 1 1021 transmits a detection signal 1070. In the frame # 1, the small cell base station # 1 1021, the small cell base station # 2 1022, and the small cell base station # 4 1024 transmit a coverage signal 1080. The small cell base station # 2 1022 and the small cell base station # 4 1024 are active and transmit the coverage signal 1080. The small cell base station # 1 1021 transmits the coverage signal 1080 together with the detection signal 1070 since the dormant state or the transmission period of the detection signal 1070 has arrived. At this time, since the small cell base station # 1 1021 is in a dormant state, the load level is lower than that of the small cell base station # 2 1022 and the small cell base station # 4 (1024). Accordingly, a larger number of tones are punctured in the coverage signal 1080 of the small cell base station # 1 1021.

In frame # 2, the small cell base station # 2 1022 transmits a detection signal 1070. In the frame # 2, the small cell base station # 2 1022 and the small cell base station # 4 1024 transmit a coverage signal 1080. The small cell base station # 2 1022 and the small cell base station # 4 1024 are active and transmit the coverage signal 1080. In this case, the load level of the small cell base station # 4 (1024) is lower than that in the frame # 1, so that a larger number of tones are punctured in the coverage signal 1080 of the small cell base station # 4 (1024). do.

In frame # 3, the small cell base station # 3 1023 transmits a detection signal 1070. In the frame # 3, the small cell base station # 2 1022, the small cell base station # 3 1023, and the small cell base station # 4 1024 transmit a coverage signal 1080. The small cell base station # 2 1022 and the small cell base station # 4 1024 are active and transmit the coverage signal 1080. The small cell base station # 3 1023 transmits the coverage signal 1080 together with the detection signal 1070 since the dormant state or the transmission period of the detection signal 1070 has arrived. At this time, since the small cell base station # 3 (1023) is dormant, the load level is lower than that of the small cell base station # 2 1022. Accordingly, a larger number of tones are punctured in the coverage signal 1080 of the small cell base station # 3 1023.

In frame # 4, the small cell base station # 4 1024 transmits a detection signal 1070. In frame # 4, the small cell base station # 2 1022 and the small cell base station # 4 1024 transmit a coverage signal 1080. The small cell base station # 2 1022 and the small cell base station # 4 1024 are active and transmit the coverage signal 1080. In this case, the load level of the small cell base station # 4 (1024) is higher than that in the frame # 3, so that fewer tones are punctured in the coverage signal 1080 of the small cell base station # 4 (1024). .

In the embodiment shown in FIG. 10, the detection signal 1070 and the coverage signal 1080 are multiplexed in one frame. However, according to another exemplary embodiment, the detection signal 1070 and the coverage signal 1080 may be multiplexed based on a frame or subframe. In this case, the frame transmitting the detection signal 1070 and the frame transmitting the coverage signal 1080 may be bundled in a pair and operated similarly to the method of FIG. 10.

In the embodiment shown in FIG. 10, the detection signal 1070 and the coverage signal 1080 are multiplexed on the time axis. However, according to another embodiment of the present invention, the detection signal 1070 and the coverage signal 1080 may be multiplexed in the frequency axis, or multiplexed in a resource domain other than the time axis or the frequency axis.

In the embodiment illustrated in FIG. 10, the small cell may inform the degree of load by partially punching the tones of the coverage signal. However, according to another embodiment of the present invention, the small cell may inform the load level by adjusting the transmission power of the coverage signal. As a specific example, when the load level is 80% or more, the coverage signal may be transmitted using the maximum power allocated to the coverage signal. When the load level is 30% to 80%, the coverage signal can be transmitted using 50% of the power allocated to the coverage signal. If the load level is less than 30%, the coverage signal can be transmitted using 30% of the power allocated to the coverage signal.

As described above, the discovery channel according to the embodiment of the present invention delivers a detection signal and a coverage signal. Further, the coverage of the detection signal and the coverage of the coverage signal are different. Accordingly, the mobile terminal may not receive both the detection signal and the coverage signal, may receive only the detection signal, or may receive both the detection signal and the coverage signal, depending on the location. have.

Accordingly, the terminal according to an embodiment of the present invention can change the measurement method of the discovery signal according to the reception situation of the discovery signal. Here, the measurement procedure may be defined by a measurement period and a measurement parameter. For example, a reception situation of the discovery signal may include a first situation in which neither the detection signal nor the coverage signal is received, a second situation in which only the detection signal is received, or both the detection signal and the coverage signal are received. It can be divided into a third situation. In this case, the terminal may apply different types of measurement periods according to each situation. The terminal may determine whether the discovery signal is received by comparing the strength of the received signal or the signal-to-interference and noise ratio (SINR) of the received signal with a predefined threshold value.

The reception situation of the discovery signal can be easily extended to the case where two or more small cells are present. For example, the reception situation of the discovery signal is a first situation in which both the detection signal and the coverage signal of all the small cells are not received, the detection signal transmitted by one or more small cells is received, but the coverage signal is all It may be classified into a second situation not received from the small cell, a third situation in which both the detection signal and the coverage signal transmitted by one or more small cells are received. Even if two or more small cells exist, the terminal may apply a different type of measurement period according to each situation.

An example of the measurement operation of adjusting the measurement period according to the above situation is as shown in FIG. 11. 11 illustrates an example of a measurement event result of a mobile terminal in a wireless communication system according to an exemplary embodiment of the present invention. 11 illustrates measurement targets, measurement intervals, and measurement events of a terminal passing through one small cell. In FIG. 11, the dotted line circle represents the coverage of the detection signal, and the solid line circle represents the coverage of the coverage signal.

Referring to FIG. 11, the terminal 1130 enters the left side of the small cell 1120 and leaves the right side. When the terminal 1130 is located outside the detection signal coverage of the small cell 1120, the terminal 1130 is in a first situation, that is, the terminal 1130 is the detection signal 1170 and the coverage signal. (1180) It is a situation that can not receive all. In the first situation, the terminal 1130 applies a first-type period 1191. For example, the first type period 1191 may be 1 sec. In addition, the terminal 1130 attempts to detect only the detection signal 1170. That is, the terminal 1130 attempts to detect the detection signal 1170 periodically according to the type 1119.

Thereafter, when the terminal 1130 enters out of the coverage 1150 of the coverage signal 1180 and into the coverage 1160 of the detection signal 1170, the terminal 1130 is in a second situation, that is, the The terminal 1130 may receive the detection signal 1170 and may not receive the coverage signal 1180. In the second situation, after successfully detecting the detection signal 1170 of the small cell 1120, the terminal 1130 applies a second-type period 1192. The second type period 1192 may be shorter than the first type period 1119. For example, the second type period 1192 may be 200 msec. After the detection of the detection signal 1170 is successful, the terminal 1130 attempts to detect both the detection signal 1170 and the coverage signal 1180. That is, the terminal 1130 attempts to detect the detection signal 1170 and the coverage signal 1180 periodically according to the two periods 1192.

Then, when the terminal 1130 enters into the coverage 1150 of the coverage signal 1180, the terminal 1130 is in a third situation, that is, the terminal 1130 is the detection signal 1170 and the In this situation, all of the coverage signals 1180 may be received. In the third situation, after successfully detecting the coverage signal 1180 of the small cell 1120, the terminal 1130 applies a third-type period 1193. The third type period 1193 may be shorter than the first type period 1191. For example, the third type period 1192 may be 200 msec. After the successful detection of the coverage signal 1180, the terminal 1130 attempts to detect both the detection signal 1170 and the coverage signal 1180. That is, the terminal 1130 attempts to detect the detection signal 1170 and the coverage signal 1180 periodically according to the three periods 1193.

Thereafter, when the terminal 1130 leaves the coverage 1150 of the coverage signal 1180, the terminal 1130 receives a second situation, that is, the terminal 1130 receives the detection signal 1170. In this case, the coverage signal 1180 is lost. In the second situation, by failing to detect the coverage signal 1180 of the small cell 1120, the terminal 1130 determines the departure of service coverage. Accordingly, the terminal 1130 applies the second type period 1192 and attempts to detect both the detection signal 1170 and the coverage signal 1180.

Thereafter, when the terminal 1130 leaves the coverage 1160 of the detection signal 1170, the terminal 1130 is in a first situation, that is, the terminal 1130 is connected to the detection signal 1170. The coverage signal 1180 may not be received. In the first situation, by failing to detect the detection signal 1170 of the small cell 1120, the terminal 1130 leaves the coverage 1160 of the detection signal 1170 of the small cell 1120. To judge. Accordingly, the terminal 1130 applies the first type period 1192 and attempts to detect the detection signal 1170. In other words, the terminal 1130 stops attempting to detect the coverage signal 1180.

The embodiment described with reference to FIG. 11 is an example in which the terminal 1130 passes through the coverage of the coverage signal 1180. However, a measurement procedure different from the example of FIG. 11 may be performed according to the movement path, such that the terminal 1130 does not pass through the coverage of the coverage signal 1180.

In the case of the embodiment of FIG. 11, the first type period 1191, the second type period 1192, and the third type period 1193 are applied to the first, second, and third situations. Is optionally applied accordingly. However, according to various embodiments of the present disclosure, each of the measurement procedures having the first type period 1191, the second type period 1192, and the third type period 1193 may be performed in the first situation, the It may be carried out in one or more of the second situation, the third situation. In this case, the terminal 1130 may perform a measurement procedure based on a plurality of periods in each situation.

According to another embodiment of the present invention, the measurement procedure corresponding to the first type period 1191 and the first type period 1191 may be always operated regardless of the measurement result of the discovery signal. For example, the measurement procedure may be performed as shown in FIG. 12. 12 illustrates another example of a measurement event result of a mobile terminal in a wireless communication system according to an exemplary embodiment of the present invention. Referring to FIG. 12, a measurement procedure 1291 corresponding to a first type period is performed according to the first type period. At this time, even if the measurement procedure (1292) corresponding to the second type period and the measurement procedure (1293) corresponding to the third type period are performed in the second and third situations, the measurement of the discovery signal and other reference signals is performed. For this purpose, the measurement procedure 1291 corresponding to the first type period may be continuously performed.

According to another embodiment of the present invention, the measurement procedure corresponding to the second type period 1192 and the second type period 1192 may be performed in addition to the second situation. For example, the measurement procedure may be performed as shown in FIG. 13. 13 illustrates another example of a measurement event result of a mobile terminal in a wireless communication system according to an exemplary embodiment of the present invention. Referring to FIG. 13, after the measurement procedure 1391 corresponding to the first type period, the measurement procedure 1392 corresponding to the second type period is performed. In this case, the measurement procedure 1372 corresponding to the second type period may be operated to measure a discovery signal or other reference signal in a situation in which a detection signal is received, and furthermore, the discovery signal or other reference may be performed even in the third situation. Can be used for the measurement of the signal. That is, as shown in FIG. 13, the measurement procedure 1392 corresponding to the second type period may be continuously performed while the measurement procedure 1393 corresponding to the third type period is performed.

According to still another embodiment of the present invention, unlike FIG. 13, in the measurement procedure 1391 corresponding to the first type period, the measurement procedure 1392 corresponding to the second type period, and in the third type period. The corresponding measurement procedure 1393 can be performed simultaneously.

According to another embodiment of the present invention, the measurement procedure corresponding to the type 3 period 193 and the type 3 period 1 193 may include the situation in which a coverage signal is detected or a reception performance of the coverage signal is greater than or equal to a specific value. In a third situation it may be operated for the measurement of the discovery signal or the other reference signal.

14 illustrates an example of movement paths of a terminal in a wireless communication system according to an exemplary embodiment of the present invention. FIG. 14 illustrates a situation in which four small cells 1421 to 1424 are located adjacent to each other, wherein the small cell # 2 1422 and the small cell # 4 1424 are in an active state, and the small cell # 1 1421 and the small cell # are located. Illustrate the case where 3 (1423) is a sleep state. In FIG. 14, the solid line indicates coverage of the coverage signal and the dotted line means coverage of the detection signal.

Referring to path # 1 1401, the terminal passes through detection signal coverage of small cell # 31423 and detection signal coverage of small cell # 1 1421. Accordingly, the terminal is placed in a first situation, a second situation in the small cell # 3 1423, a second situation in the small cell # 1 1421, and a first situation according to time.

Referring to path # 2 1402, the terminal passes through detection signal coverage of small cell # 2 1422, coverage signal coverage of small cell # 2 1422, and detection signal coverage of small cell # 1 1421. . Accordingly, the UE may perform a first situation, a second situation in the small cell # 2 1422, a third situation in the small cell # 2 1422, and a third situation in the small cell # 2 1422. In two situations, the small cell # 1 1421 is placed in the second and first situations.

Referring to path # 3 1403, the terminal passes through detection signal coverage of small cell # 3 1423, coverage signal coverage of small cell # 31423, and detection signal coverage of small cell # 41424. . Accordingly, the UE may perform a first situation, a second situation in the small cell # 3 1423, a third situation in the small cell # 3 1423, and a third situation in the small cell # 3 1423 according to time. In the second situation, the first situation, the small cell # 4 1424 is placed in the second situation and the first situation.

Hereinafter, the operation and configuration of a terminal, a macro base station, and a small cell base station for performing small cell measurement as described above will be described with reference to the accompanying drawings.

Referring to FIG. 15, the terminal attempts to detect a signal to be measured in step 1501. The signal to be measured depends on the type of discovery signal that is currently received, that is, currently detectable (eg, detection signal, coverage signal). For example, when the terminal cannot detect both the detection signal and the coverage signal, the measurement object includes the detection signal. As another example, when the terminal can detect the detection signal, the measurement object includes the detection signal and the coverage signal. As another example, when the terminal can detect both the detection signal and the coverage signal, the measurement object includes the detection signal and the coverage signal.

In step 1501, the period at which the UE measures the target signal and a measurement parameter vary according to the type of discovery signal (eg, detection signal and coverage signal) currently detectable. For example, the terminal receives a first situation in which both the detection signal and the coverage signal of all small cells are not received, the detection signal transmitted by one or more small cells is received, but the coverage signal is received from all small cells. Different types of measurement periods and measurement parameters may be applied according to a second situation in which the second situation does not occur, and the third situation in which both the detection signal transmitted by one or more small cells and the coverage signal are received. Can be. However, according to various embodiments of the present disclosure, the terminal may apply all different types of measurement periods and measurement parameters for the different situations. That is, the terminal may apply the measurement periods and the measurement parameters defined for each situation to other situations. In other words, the terminal may independently perform a plurality of measurement procedures defined for each situation.

After the detection attempt, the terminal proceeds to step 1503 and determines whether the detection of at least one of the detection signal and the coverage signal is successful. Here, the determination method of whether the detection is successful may vary depending on the structure of the detection signal and the coverage signal. For example, the detection signal and the coverage signal may be configured in a predefined sequence, such as a synchronization signal, or may be configured to be transmitted on some tones along with data symbols. For example, the terminal may determine whether the detection is successful by performing a correlation operation. In addition, the terminal may determine whether the detection signal and the coverage signal is received by comparing the strength of the received signal or the signal-to-interference and noise ratio (SINR) of the received signal with a predefined threshold. If neither the detection signal nor the coverage signal is detected, the terminal returns to step 1501 while maintaining the measurement object. Thereafter, the detection attempt in step 1501 is performed after a predetermined period elapses.

If at least one of the detection signal and the coverage signal is detected, the terminal proceeds to step 1505 and transmits a measurement report (MR) corresponding to the small cell state. The measurement report is based on the type of detected signal, the type of lost signal, identification information of the small cell that transmitted the detected signal, the operating state (eg, active state, dormant state) of the small cell, and the detected signal. It may include information on at least one of the determined channel quality. That is, the terminal checks the identification information of the small cell and the operation state of the small cell through at least one of the detected detection signal and the coverage signal, and transmits the measurement report. In this case, the terminal may transmit the report to the macro base station or the small cell base station. If the small cell in which the discovery signal is detected is in the dormant state and only the detection signal of the small cell is detected and the coverage signal is not detected, the terminal may not report the measurement result for the small cell. In this way, the small cell in the dormant state can be prevented from unnecessarily wake-up. In addition, when the small cell in which the discovery signal is detected is active and only the detection signal of the small cell is detected and the coverage signal is not detected, the terminal may not report the measurement result for the small cell. In this way, excessive power consumption of the terminal can be prevented by reducing the number of times the terminal reports the measurement result.

After transmitting the measurement report, the terminal proceeds to step 1507 to determine the measurement period, measurement parameters and the measurement target. The measurement period, the measurement parameter and the measurement object are determined based on the type of discovery signal currently received, that is to say currently detectable. Accordingly, when the type of detectable discovery signal is changed, the measurement period, the measurement parameter, and the measurement object may be changed. For example, when the terminal cannot detect both the detection signal and the coverage signal, the measurement object includes the detection signal. As another example, when the terminal can detect the detection signal, the measurement object includes the detection signal and the coverage signal. As another example, when the terminal can detect both the detection signal and the coverage signal, the measurement object includes the detection signal and the coverage signal. Further, the first measurement period when neither the detection signal nor the coverage signal is detected is the second measurement period when only the detection signal is detected, and the third measurement period when both the detection signal and the coverage signal are detected. It may be longer than the measurement cycle. However, according to various embodiments of the present disclosure, two or more of the measurement procedure corresponding to the first measurement period, the measurement procedure corresponding to the second measurement period, and the measurement procedure corresponding to the third measurement period are performed in parallel. Can be.

In the embodiment illustrated in FIG. 15, when at least one discovery signal is detected, the terminal transmits a measurement report. However, according to another embodiment of the present invention, even if at least one discovery signal is detected, the terminal may not transmit the measurement report. For example, when at least one of the detection signal and the coverage signal is repeatedly detected in every measurement period, the terminal may not retransmit the measurement report while the detection is maintained. That is, the terminal may transmit the measurement report only when at least one of the detection signal and the coverage signal is additionally detected or additionally lost.

16 illustrates an operation procedure of a macro base station in a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 16, the macro base station determines parameters for measuring at least one small cell in step 1601. The parameters may include measurement periods for each situation, discovery channel allocation information, transmission periods of discovery signals for each small cell base station, information items included in the measurement report, and time points at which the measurement report is transmitted (for example, detection signal detection, coverage signal detection, and coverage signal Loss, detection signal loss).

Thereafter, the macro base station proceeds to step 1603 to transmit the determined parameters. In this case, some of the parameters may be transmitted to the small cell base station and some to the terminal. For example, the macro base station may provide the discovery channel allocation information and the transmission period of the discovery signal for each small cell base station to the small cell base stations in the macro cell. The macro base station may further include a measurement period for each situation, the discovery channel allocation information, a transmission period of a discovery signal for each small cell base station, an information item included in the measurement report, and the measurement report to terminals in a macro cell. A viewpoint and the like can be transmitted. Here, the macro base station may transmit the parameters to the terminals through a broadcast channel or a unicast message.

Referring to FIG. 17, the small cell base station determines the operation state in step 1701. The operating state is one of an active state and a dormant state. The active state refers to a state in which at least one terminal is connected to the small cell, and the small cell communicates. The dormant state refers to a situation in which a terminal connected to the small cell does not exist, and the small cell does not communicate with the terminal.

If the small cell base station is active, the small cell base station proceeds to step 1703 and periodically transmits a detection signal in the detection signal region of the discovery channel, and transmits a coverage signal in all the coverage signal regions of the discovery channel. . That is, the small cell base station continuously transmits the coverage signal. The small cell base station periodically transmits the detection signal. Here, the transmission period of the detection signal may be indicated from the macro base station or from a separate control node. The detection signal is scheduled to be transmitted exclusively between a plurality of small cell base stations. According to an embodiment of the present disclosure, some tones of the coverage signal may be punctured according to the load level of the small cell base station. In addition, the transmission power of the coverage signal may be set according to the load level of the small cell base station.

If the small cell base station is in the dormant state, the small cell base station proceeds to step 1705 to periodically transmit the detection signal in the detection signal region of the discovery channel, and periodically in the coverage signal region of the discovery channel. Send. The detection signal is scheduled to be transmitted exclusively between a plurality of small cell base stations. In this case, the transmission period of the detection signal and the transmission period of the coverage signal are the same, and the coverage signal is transmitted through a coverage area paired with the detection signal area in which the detection signal is transmitted. For example, when the detection signal region and the coverage signal region are allocated in one frame as shown in FIG. 5, the small cell base station may transmit the coverage signal in a frame in which the detection signal is transmitted. Here, the transmission period of the detection signal and the coverage signal may be indicated from the macro base station or from a separate control node.

Referring to FIG. 18, the terminal includes a radio frequency (RF) processor 1810, a baseband processor 1820, a storage 1830, and a controller 1840.

The RF processor 1810 performs a function for transmitting and receiving a signal through a wireless channel such as band conversion and amplification of the signal. That is, the RF processor 1810 up-converts the baseband signal provided from the baseband processor 1820 to an RF band signal and transmits the same through an antenna, and transmits an RF band signal received through the antenna to a baseband signal. Downconvert to. For example, the RF processor 1810 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), and the like. . In FIG. 18, only one antenna is illustrated, but the terminal may include a plurality of antennas. In addition, the RF processor 1810 may include a plurality of RF chains.

The baseband processor 1820 performs a conversion function between the baseband signal and the bit string according to the physical layer standard of the system. For example, during data transmission, the baseband processor 1820 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processor 1820 restores the received bit string by demodulating and decoding the baseband signal provided from the RF processor 1810. For example, according to the OFDM scheme, during data transmission, the baseband processor 1820 generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then IFFT (Inverse). OFDM symbols are constructed through Fast Fourier Transform (CP) operation and Cyclic Prefix (CP) insertion. In addition, when receiving data, the baseband processor 1820 divides the baseband signal provided from the RF processor 1810 in OFDM symbol units, and performs the signals mapped to the subcarriers through a fast fourier transform (FFT) operation. After recovery, the reception bit stream is restored by demodulation and decoding. The baseband processor 1820 and the RF processor 1810 transmit and receive signals as described above. Accordingly, the baseband processor 1820 and the RF processor 1810 may be referred to as a transmitter, a receiver, or a transceiver.

The storage unit 1830 stores data such as a basic program, an application program, and setting information for the operation of the terminal. For example, the storage 1830 may store setting parameters required for measuring the small cell. The storage unit 1830 provides stored data at the request of the controller 1840.

The controller 1840 controls the overall operations of the terminal. For example, the controller 1840 transmits and receives a signal through the baseband processor 1820 and the RF processor 1810. According to an embodiment of the present disclosure, the controller 1840 includes a measurement manager 1842 for controlling functions for discovering a small cell. For example, the controller 1840 controls the terminal to perform the procedure shown in FIG. 15. Operation of the control unit 1840 according to an embodiment of the present invention is as follows.

According to an embodiment of the present disclosure, the controller 1840 attempts to detect a measurement target signal. The signal to be measured depends on the type of discovery signal that is currently received, that is, currently detectable (eg, detection signal, coverage signal). The detection signal and the coverage signal may be configured in a predefined sequence, such as a synchronization signal, or may be configured to be transmitted on some tones along with data symbols.

When at least one of the detection signal and the coverage signal is detected, the controller 1840 generates a measurement report corresponding to the small cell state, and transmits the measurement report to the baseband processor 1820 and the RF processor 1810. Send via). For example, the controller 1840 may transmit the measurement report when at least one of the detection signal and the coverage signal is additionally detected or additionally lost. The measurement report may include information on at least one of a type of a detected signal, a type of a lost signal, identification information of a small cell transmitting the detected signal, and an operating state (eg, an active state or a dormant state) of the small cell. It may include. In this case, the controller 1840 may transmit the report to the macro base station or the small cell base station. The controller 1840 determines the measurement period and the measurement target based on the type of discovery signal currently detectable. However, according to various embodiments of the present disclosure, two or more of the measurement procedure corresponding to the first measurement period, the measurement procedure corresponding to the second measurement period, and the measurement procedure corresponding to the third measurement period are performed in parallel. Can be.

19 is a block diagram of a base station in a wireless communication system according to an embodiment of the present invention. 19 may be applied to a macro base station or a small cell base station.

As illustrated in FIG. 19, the base station includes an RF processor 1910, a baseband processor 1920, a backhaul communication unit 1930, a storage unit 1940, and a controller 1950.

The RF processor 1910 performs a function for transmitting and receiving a signal through a wireless channel such as band conversion and amplification of the signal. That is, the RF processor 1910 up-converts the baseband signal provided from the baseband processor 1920 to an RF band signal and transmits the same through an antenna, and transmits an RF band signal received through the antenna to a baseband signal. Downconvert to. In FIG. 19, only one antenna is shown, but the base station may include a plurality of antennas. The RF processor 1910 may include RF chains for each of a plurality of antennas, and each RF chain may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like.

The baseband processor 1920 performs a baseband signal and bit string conversion function according to the physical layer standard of the system. For example, according to the OFDM scheme, during data transmission, the baseband processor 1920 generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then executes an IFFT operation and Compose OFDM symbols through CP insertion. In addition, when receiving data, the baseband processor 1920 divides the baseband signal provided from the RF processor 1910 in OFDM symbol units, restores signals mapped to subcarriers through an FFT operation, and demodulates the demodulated signal. And restores the received bit string through decoding. The baseband processor 1920 and the RF processor 1910 transmit and receive signals as described above. Accordingly, the baseband processor 1920 and the RF processor 1910 may be referred to as a transmitter, a receiver, or a transceiver.

The backhaul communication unit 1930 provides an interface for communicating with other nodes in the network. That is, the backhaul communication unit 1930 converts a bit string transmitted from the base station to another node, for example, another base station, a core network, etc., into a physical signal, and converts a physical signal received from the other node into a bit string. do. The storage unit 1940 stores data such as a basic program, an application program, and setting information for the operation of the base station. For example, the storage unit 1940 may store scheduling information about a discovery channel. The storage unit 1940 provides stored data at the request of the controller 1950.

The controller 1950 controls the overall operations of the base station. For example, the controller 1940 transmits and receives a signal through the baseband processor 1920 and the RF processor 1910 or through the backhaul communication unit 1930. In addition, the controller 1940 records and reads data in the storage 1940. According to an embodiment of the present disclosure, the controller 1950 controls the base station to perform the procedure illustrated in FIG. 16 or 19. Operation of the control unit 1940 according to an embodiment of the present invention is as follows.

When the base station is a macro base station, the controller 1950 determines parameters for measurement of at least one small cell. The parameters may include measurement periods for each situation, discovery channel allocation information, transmission periods of discovery signals for each small cell base station, information items included in the measurement report, and time points at which the measurement report is transmitted (for example, detection signal detection, coverage signal detection, and coverage signal). Loss, detection signal loss). The controller 1950 controls to provide the determined parameters to the terminals in the macro cell and the small cell base stations.

When the base station is a small cell base station and is in an active state, the controller 1950 periodically transmits a detection signal in the detection signal region of the discovery channel, and transmits a coverage signal in all coverage signal regions of the discovery channel. To control. In this case, according to an embodiment of the present disclosure, some tones of the coverage signal may be punctured according to the load level of the small cell base station. In addition, the transmission power of the coverage signal may be set according to the load level of the small cell base station.

When the base station is a small cell base station and in a dormant state, the controller 1950 periodically transmits the detection signal in the detection signal region of the discovery channel, and periodically in the coverage signal region of the discovery channel. Control to transmit. In this case, the transmission period of the detection signal and the transmission period of the coverage signal are the same, and the coverage signal is transmitted through a coverage area paired with the detection signal area in which the detection signal is transmitted.

Methods according to the embodiments described in the claims or the specification of the present invention may be implemented in the form of hardware, software, or a combination of hardware and software.

When implemented in software, a computer-readable storage medium for storing one or more programs (software modules) may be provided. One or more programs stored in a computer readable storage medium are configured for execution by one or more processors in an electronic device. One or more programs include instructions that cause an electronic device to execute methods in accordance with embodiments described in the claims or specification of the present invention.

Such programs (software modules, software) may include random access memory, non-volatile memory including flash memory, read only memory (ROM), and electrically erasable programmable ROM. (EEPROM: Electrically Erasable Programmable Read Only Memory), magnetic disc storage device, compact disc ROM (CD-ROM), digital versatile discs (DVDs) or other forms It can be stored in an optical storage device, a magnetic cassette. Or, it may be stored in a memory composed of some or all of these combinations. In addition, each configuration memory may be included in plural.

In addition, the program may be configured through a communication network such as the Internet, an intranet, a local area network (LAN), a wide area network (WLAN), or a storage area network (SAN), or a combination thereof. It may be stored in an attachable storage device that is accessible. Such a storage device may be connected to a device for performing an embodiment of the present invention through an external port. In addition, a separate storage device on a communication network may be connected to a device for performing an embodiment of the present invention.

In specific embodiments of the present invention described above, the components included in the invention are expressed in the singular or plural number according to the specific embodiments presented. However, the singular or plural expressions are selected to suit the circumstances presented for convenience of description, and the present invention is not limited to the singular or plural elements, and the singular or plural elements may be used in the singular or the singular. Even expressed components may be composed of a plurality.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

Claims

In the method of operation of a terminal in a wireless communication system,

Receiving a first signal indicating the presence of the small cell according to the first measurement period;

Attempting to detect the first signal and a second signal informing of service coverage of the small cell according to a second measurement period.
The method of claim 1,

And transmitting a measurement report informing of detection of the first signal.
The method of claim 2,

The measurement report may include information on at least one of a type of a detected signal, a type of a lost signal, identification information of the small cell, an operation state of the small cell, and a channel quality determined based on the detected signal. Method comprising a.
The method of claim 1,

If the first signals of the plurality of small cells are detected, transmitting the measurement report for at least one small cell except for at least one small cell that is dormant.
The method of claim 1,

The method may further include determining a measurement object according to at least one signal to be detected.
The method of claim 5,

The measurement object includes only the first signal when neither the first signal nor the second signal is detected, and includes the first signal and the second signal when only the first signal is detected. And when the first signal and the second signal are detected, the first signal and the second signal.
The method of claim 1,

If the first signal is lost, transmitting a measurement report indicating the loss of the first signal;

And stopping the detection attempt for the second signal.
The method of claim 1,

And if the second signal is detected, attempting to detect the first signal and the second signal according to a third measurement period.
The method of claim 1,

After receiving the first signal, independently of attempting to detect the second signal, attempting to detect at least one of the first signal and the reference signal according to the first measurement period. How to.
In the method of operating a small cell base station in a wireless communication system,

Periodically transmitting a first signal for notifying the presence of the small cell;

And transmitting a second signal for notifying the service coverage of the small cell.
The method of claim 10,

The process of transmitting the second signal,

And periodically transmitting the second signal while the small cell base station is operating in a dormant state.
The method of claim 10,

The process of transmitting the second signal,

Transmitting the second signal through all the second signal regions of the discovery channel while the small cell base station is active.
The method of claim 10,

The process of transmitting the second signal,

Puncturing some of the tones constituting the second signal based on the load level of the small cell base station.
The method of claim 10,

Wherein the first signal and the second signal are configured in a predefined sequence or are configured to occupy some tones of an Orthogonal Frequency Division Multiplexing (OFDM) symbol.
15. An apparatus configured to carry out the method of any one of claims 1-14.