KR102220241B1 - Apparatus and method for cell control - Google Patents

Abstract

The present invention, in a wireless environment in which a plurality of small cells within a macro cell are established, only a small cell located adjacent to a terminal among a plurality of small cells in an inactive state is switched to an active state to induce handover of a terminal connected to the macro cell. Or, by inducing reconnection of a new terminal, small cells not adjacent to the terminal are prevented from being unnecessarily switched to the active state, thereby eliminating interference between small cells and reducing power consumption of the small cell due to switching to the active state. A cell control device and cell control method that can be minimized are proposed.

Description

Cell control device and cell control method {APPARATUS AND METHOD FOR CELL CONTROL}

In a wireless environment in which a plurality of small cells in a macro cell are built, the present invention switches only a small cell located adjacent to a terminal among a plurality of small cells in an inactive state to an active state, thereby handover of a terminal connected to the macro cell and a new terminal. The present invention relates to a method for minimizing power consumption of a small cell due to switching to an active state and removing interference between small cells by inducing reconnection of

In the LTE communication system, as the type of communication service and the transmission request speed are diversified, the LTE frequency expansion and the evolution to the 5G communication system are actively progressing.

In this regard, in the 5G communication system, the HetNet technology has been proposed as a core technology as a method for solving the explosion of data traffic.

Such a hetnet technology refers to a technology that improves data processing capacity and speed through a method of constructing a plurality of small cells in one macro cell.

However, in the case of the Hetnet technology, as mentioned above, since a large number of small cells are built in one macro cell, there is a high risk of interference between small cells, and if interference occurs between the small cells, data processing capacity and speed Problems can arise in which the improvement falls short of expectations.

In the end, in order to expect an increase in data processing capacity and speed in a wireless environment that follows the Hetnet technology, it is necessary to find a way to minimize interference that may occur between small cells.

The present invention was created in view of the above circumstances, and an object to be reached in the present invention is to be located adjacent to a terminal among a plurality of small cells in an inactive state in a wireless environment in which a plurality of small cells in a macro cell are established. This is to minimize interference between small cells and minimize power consumption of the small cell due to switching to the active state by inducing handover of the terminal connected to the macro cell and reconnection of the new terminal by switching only the small cell to the active state.

A cell control apparatus according to an embodiment of the present invention for achieving the above object includes: a confirmation unit for checking a location of a terminal connected to the macro cell in a wireless environment in which a plurality of small cells are located in a macro cell; A selection unit for selecting a target small cell in an inactive state related to the location of the terminal among the plurality of small cells; And a controller configured to convert the target small cell into an active state so that the terminal can be handed over to the target small cell, or a new terminal can be reconnected to the target small cell.

More specifically, the verification unit checks the location of the terminal based on timing advance (TA) for differently determining a transmission time at which an uplink signal is transmitted from the terminal according to the distance between the macro cell and the terminal Characterized in that.

More specifically, the selector may select the target small cell based on a result of comparing the transmission time information of the terminal and the transmission time information mapped to each of the plurality of small cells.

More specifically, in the target small cell, the transmission time information identical to the transmission time information of the terminal among the plurality of small cells is mapped, or the transmission time information in which the difference from the transmission time information of the terminal is less than a threshold value is mapped. It features.

More specifically, the selector includes a first small cell and a second small cell in an inactive state related to the location of the terminal among the plurality of small cells, and the terminal is handed over from the second small cell. Thus, when it is confirmed that it is connected to the macro cell, only the first small cell is selected as the target small cell.

More specifically, the verification unit is characterized in that it checks the location of the terminal in the macro cell only when the traffic volume of the macro cell according to the access of the terminal is greater than or equal to a threshold.

More specifically, the terminal does not perform handover to the specific small cell only when it is determined that the quality measurement value related to the radio environment in the target small cell is greater than the quality measurement value related to the radio environment in the macro cell. It is characterized.

More specifically, the target small cell is characterized in that it returns to the inactive state when the terminal is not connected from the time point when the terminal is switched to the activated state until a threshold time elapses.

In the cell control method according to an embodiment of the present invention for achieving the above object, the cell control device checks the location of a terminal connected to the macro cell in a wireless environment in which a plurality of small cells in the macro cell are located. ; A selection step of selecting, by the cell control apparatus, a target small cell in an inactive state related to the location of the terminal among the plurality of small cells; And a control step of the cell control device to convert the target small cell into an activated state so that the terminal can be handed over to the target small cell, or a new terminal can be reconnected to the target small cell. It features.

More specifically, in the verification step, the location of the terminal is determined based on timing advance (TA) for differently determining a transmission time at which an uplink signal is transmitted from the terminal according to the distance between the macro cell and the terminal. It is characterized by checking.

More specifically, in the selecting step, the target small cell is selected based on a result of comparing the transmission time information of the terminal and the transmission time information mapped to each of the plurality of small cells.

More specifically, in the target small cell, the transmission time information identical to the transmission time information of the terminal among the plurality of small cells is mapped, or the transmission time information in which the difference from the transmission time information of the terminal is less than a threshold value is mapped. It features.

More specifically, the selection step is related to the location of the terminal among the plurality of small cells, and there are a first small cell and a second small cell in an inactive state, and the terminal is handed from the second small cell. When it is confirmed that it is over and connected to the macro cell, only the first small cell is selected as the target small cell.

Accordingly, according to the cell control apparatus and the cell control method of the present invention, in a wireless environment in which a plurality of small cells in a macro cell are established, only a small cell located adjacent to a terminal among a plurality of small cells in an inactive state is switched to an active state. Thus, by inducing handover of the terminal connected to the macro cell, the small cell that is not adjacent to the terminal is prevented from being unnecessarily switched to the active state, thereby eliminating interference between small cells and power of the small cell according to the transition to the active state. The effect of minimizing consumption is achieved.

1 is an exemplary diagram showing a wireless environment according to an embodiment of the present invention.
2 is a diagram showing a schematic configuration of a cell control apparatus according to an embodiment of the present invention.
3 to 5 are views for explaining transmission time information (TA) according to an embodiment of the present invention.
6 and 7 are exemplary views for explaining an activation state switching operation according to an embodiment of the present invention.
8 is a view for explaining the operation flow in the cell control apparatus according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

1 shows a wireless environment according to an embodiment of the present invention.

As shown in FIG. 1, in a wireless environment according to an embodiment of the present invention, a plurality of small cells (SC11, SC12, S14, SC15) are built in a macro cell, for example, a core technology in a 5G communication system. HetNet) technology.

In addition, in the wireless environment according to an embodiment of the present invention, it can be seen that the UE#0 is located in an area where the cell control apparatus 10 and the macro cell and the small cell SC12 overlap.

Here, the cell control device 10 refers to a base station device that provides a mobile communication service to a terminal located in the macro cell by forming a macro cell having a radius of about several km or less as an area. For example, NodeB, eNodeB This may be the case.

In addition, the UE#0 may collectively refer to a mobile or fixed user node such as, for example, a user equipment (UE) or a mobile station (MS).

Each small cell (SC11, SC12, S14, SC15) may be constructed with a radius of about several tens m in each area overlapping with the macro cell area as an area, and such small cells include, for example, femto cells, pico cells. Cell, home node B, and home EnB may correspond.

Meanwhile, each of the small cells SC11, SC12, S14, and SC15 according to an embodiment of the present invention is automatically switched to an inactive state when the number of terminals (traffic amount) connected to it is less than a threshold.

At this time, each of the small cells SC11, SC12, S14, and SC15 guarantees service continuity for the UE by handing over the already connected UE to the macro cell and then switching to the inactive state.

As such, each of the small cells SC11, SC12, S14, and SC15 converted to the inactive state can minimize power consumption and do not cause any interference with other small cells.

However, when each small cell (SC11, SC12, S14, SC15) is in the active state, each small cell (SC11, SC12, S14, SC15) is a reference signal related to cell identification (e.g., CRS, Cell-Specific Reference). Signal) must be continuously transmitted, and such a reference signal may cause interference between small cells (SC11, SC12, S14, and SC15).

As a result, the risk of minimizing the occurrence of interference between small cells (SC11, SC12, S14, SC15) and power consumption in each of the small cells (SC11, SC12, S14, SC15) is inactive small cells (SC11, SC12, SC15). It can be seen that it is very important to convert each of S14 and SC15) into the active state in what situation and in what manner.

In this regard, in an embodiment of the present invention, in a manner in which each of the small cells SC11, SC12, S14, and SC15 in an inactive state is switched to an active state, for example, the small cells SC11, SC12, S14, and SC15 are Each of the small cells (SC11, SC12, S14, SC15) is changed to the activated state according to the method of voluntarily switching to the activated state (hereinafter referred to as the'first switching method'), and the control of the cell controller 10. A method of uniform conversion (hereinafter referred to as a'second conversion method') may be followed.

First, a case in which the wireless environment according to an embodiment of the present invention follows the first switching method will be described as follows.

In order for the wireless environment according to an embodiment of the present invention to follow the first switching scheme, each of the small cells (SC11, SC12, S14, and SC15) must be able to measure interference and noise in its own region even in an inactive state.

To this end, each of the macro cells and small cells (SC11, SC12, S14, SC15) must use the same frequency band, and in particular, each of the small cells (SC11, SC12, S14, SC15) interferes within its own area even in the inactive state. It should be premised that the uplink receiver chain is kept on in order to measure noise and noise.

On the premise of such a wireless environment, when a terminal (UE#0) located in an area where the macro cell and the small cell (SC 12) overlap to access the network, each of the small cells (SC11, SC12, S14, and SC15) is non- Since the state is switched to the active state, the terminal UE#0 accesses the macro cell.

At this time, the small cell (SC 12) detects an increase in interference and noise according to the connection of the terminal (UE#0) in the macro cell area overlapped with the self-area, and accordingly activates its state in the inactive state. By switching to the state and transmitting a reference signal (CRS) for cell identification to its own region, access (handover) of the UE (UE#0) that has received it is induced.

In this regard, the UE#0 compares the wireless environment of the macro cell and the wireless environment of the small cell SC 12. As a result of the comparison, the wireless environment of the small cell SC 12 is better than that of the macro cell. In this case, the handover is performed from the macro cell to the small cell SC 12.

If the terminal (UE#0) is not connected (handover) until a certain time elapses from the time the small cell (SC 12) is switched to the active state, the small cell (SC 12) is used to minimize power consumption. It will of course return one's state to the inactive state.

After all, when the wireless environment according to an embodiment of the present invention follows the first switching scheme, only the small cells adjacent to the UE #0 among the small cells SC11, SC12, S14, and SC15 that are in an inactive state are activated. It can be seen that the effect of minimizing interference that may occur between the small cells SC11, SC12, S14, and SC15 can be achieved as the state is switched.

However, in the first switching method, each of the small cells (SC11, SC12, S14, SC15) has to keep the uplink receiver chain on to measure interference and noise in its own area. (SC11, SC12, S14, SC15) It can be expected that there is a limit to minimizing power consumption in each.

Next, a case in which the wireless environment according to an embodiment of the present invention follows the second switching method will be described as follows.

For reference, when the wireless environment according to an embodiment of the present invention follows the second switching scheme, it may be premised that each of the macro cells and the small cells (SC11, SC12, S14, and SC15) use different frequency bands. .

On the premise of such a wireless environment, when a terminal (UE#0) located in an area where the macro cell and the small cell (SC 12) overlap to access the network, each of the small cells (SC11, SC12, S14, and SC15) is non- Since the state is switched to the active state, the terminal UE#0 accesses the macro cell.

At this time, when the number of terminals connected to the macro cell (amount of traffic) exceeds the threshold value according to the access of the terminal (UE#0), the cell controller 10 may be handed over to the small cell. All of the small cells (SC11, SC12, S14, SC15) in the inactive state are switched to the activated state.

In this regard, the terminal (UE#0) compares the wireless environment of the macro cell and the wireless environment of each of the small cells (SC11, SC12, S14, SC15). If a small cell (eg SC 12) exists, handover is performed to the small cell.

If the terminal (UE#0) is not connected (handover) until a certain time elapses from the time when each of the small cells (SC11, SC12, S14, SC15) is switched to the active state, each small cell (SC11) , SC12, S14, SC15) will of course return their state to the inactive state to minimize power consumption.

After all, when the wireless environment according to an embodiment of the present invention follows the second switching method, when each of the small cells (SC11, SC12, S14, and SC15) is in an inactive state, any operation unlike the first switching method It can be seen that the effect of minimizing power consumption in each of the small cells SC11, SC12, S14, and SC15 is achieved, as this is not achieved.

However, in the second switching method, as the switching to the active state for each of the small cells (SC11, SC12, S14, SC15) is uniformly performed under the control of the cell controller 10, the terminal (UE#0) is Not only the small cell SC12 but also the remaining small cells SC11, S14, and SC15 not adjacent to the terminal are switched to the active state.

Accordingly, each of the small cells (SC11, SC12, S14, SC15) existing in the macro cell transmits a reference signal (CRS) for cell identification according to the transition to the active state, and thus each small cell (SC11, The reference signal CRS transmitted from the SC12, S14, and SC15 has a limitation that causes interference between the small cells SC11, SC12, S14, and SC15.

Accordingly, in an embodiment of the present invention, power consumption of each small cell and interference between small cells in a wireless environment in which a plurality of small cells in a macro cell are constructed in order to solve the limitations of the first and second switching methods above. To propose a new method for minimizing the interference, hereinafter, the configuration of the cell control device 10 for implementing this will be described in detail.

2 is a diagram showing a schematic configuration of a cell control device 10 according to an embodiment of the present invention.

As shown in FIG. 2, the cell control apparatus 10 according to an embodiment of the present invention includes a checker 11 for checking the location of a terminal (UE#0), a plurality of small cells SC11, SC12, S14. , SC15), including a selection unit 12 for selecting a target small cell to be handed over to the UE #0, and a control unit 13 for controlling the UE #0 to be handed over to the target small cell It can have a configuration.

The entire configuration or at least a part of the cell control device 10 including the confirmation unit 11, the selection unit 12, and the control unit 13 is implemented in the form of a software module or a hardware module, or a software module and a hardware module are It can be implemented in a combined form.

As a result, the cell control apparatus 10 according to an embodiment of the present invention minimizes power consumption of each small cell and interference between small cells in a wireless environment in which a plurality of small cells in a macro cell are built through the above configurations. In the following, each configuration of the cell control device 10 for this will be described in detail.

The check unit 11 performs a function of checking the location of the terminal UE#0.

More specifically, the verification unit 11 checks the location of the terminal UE#0 connected to the macro cell according to the deactivation state of each of the plurality of small cells SC11, SC12, S14, and SC15.

In this way, checking of the terminal (UE#0) connected to the macro cell is for handing over the terminal (UE#0) to a specific small cell adjacent to the current location of the terminal (UE#0) in the macro cell. #0) This can be done only when the number of terminals (traffic amount) connected to the macro cell is greater than or equal to the threshold value according to the connection.

At this time, the verification unit 11 may check the location of the UE #0 in the macro cell through a method of checking the transmission timing information (TA) of the UE#0.

Here, the transmission time information (TA) is information for synchronizing the uplink time between the cell control device 10 and the terminal (UE#0), and indicates the transmission time of transmitting the uplink signal from the terminal (UE#0). You decide.

Such, transmission time information (TA) is determined by the cell control device 10 that has received the RACH preamble transmitted from the UE (UE#0), the cell control device 10 is the terminal (UE#0) Determine how much to adjust the transmission timing of the reverse signal (uplink signal) of the UE (UE#0) based on the time difference between the time when the RACH preamble is received from) and the start point of the downlink radio frame, The adjustment value of the transmission timing of the reverse signal may be determined as transmission time information TA.

In the end, the transmission time information (TA) is an offset value defined to determine the transmission time at which the uplink signal is transmitted from the terminal, for example, from'TA=0' to'TA=63'. It may have, and as the value increases, it may indirectly mean that the distance between the cell control apparatus 10 and the UE #0 increases.

Accordingly, the verification unit 11 checks the value of the transmission time information (TA) of the terminal (UE#0) connected to the macro cell, and converts the confirmed value into units of, for example,'km' or'msec', It is possible to directly determine the location of the UE# in the cell.

Hereinafter, the above-mentioned transmission time information (TA) will be described in more detail. Meanwhile, the base station mentioned below corresponds to the cell control device 10 in an embodiment of the present invention.

3 shows a relationship between a transmission time point of a downlink radio frame and an uplink radio frame transmission time defined in the standard.

만큼 앞당겨져 전송되는 것을 확인할 수 있다. 여기서,

,

,

(FDD 방식인 경우)As shown in FIG. 3, the transmission time of an uplink radio frame i for synchronization of an uplink subframe in the base station is based on a downlink radio frame i.

You can see that it is transmitted ahead of time. here,

,

,

(In case of FDD method)

The difference between the transmission timing of the downlink radio frame and the transmission timing of the uplink radio frame may be used to determine a value of transmission timing information (TA).

That is, the initial transmission time information (TA) can be determined by converting from a time difference between the transmission time of the RACH preamble transmitted from the terminal and the transmission time of the downlink radio frame when the terminal is initially accessed (Random Access).

At this time, the transmission time information (TA) is converted to a value in the range of 0 to 1280 (0,1,2,..,1282), and can be transmitted to the terminal as an 11-bit TAC value in the periodic random access response (RAR). have.

Thereafter, when the RACH preamble is received from the UE, the difference from the transmission time point before the RACH preamble is calculated, the calculated time difference is determined as a value of the transmission time information (TA) in the range of 0 to 63, It can be delivered to the terminal as a TAC value.

This, transmission time information (TA) is a value for adjusting the transmission time of the uplink subframe (eg, PUSCH / PUCCH / SRS, etc.) of the terminal according to the distance change between the base station and the terminal, as mentioned above, within the RAR. By being transmitted to the terminal as a TAC value, it can be used to maintain synchronization when the base station receives an uplink subframe (eg, PUSCH/PUCCH/SRS, etc.).

For example, if the timing at which an uplink subframe is received from the terminal is the same based on the initial TAC value (when there is no change in the distance between the base station and the terminal), the base station calculates this and calculates the value of the transmission time information (TA). It can be determined as 31 and delivered to the terminal.

If the terminal is away from the base station, the level of the distance is calculated, the TA value is increased to 32, and the increased TA value is included in the TAC value in the RAR and transmitted to the terminal. It is possible to advance the transmission time of the link subframe by approximately 0.52us.

Here, the value of the transmission time information TA may have a range of 0 to 63, as mentioned above, and in order to convert the value of the transmission time information TA into an actual uplink subframe transmission time, for example, You can follow [Equation 1].

[Equation 1]

Uplink subframe transmission time = (previous uplink subframe transmission time) + (TA value-31) x 16 samples,

Here, a time length of one sample (1 sample) is approximately 0.033 us, and 16 samples have a time length of approximately 0.52 us, whereby the uplink subframe transmission time is transmission time information having a range of 0 to 63 ( It can be seen that depending on the value of TA), it can be changed to a maximum length of 16.7us.

In this regard, FIGS. 4 and 5 show examples of MAC Protocol Data Unit (PDU) related to transmission time information TA.

As shown in Fig. 4, the initial two bits in one byte are reserved fields and always have a value of'O', and the remaining six fields have a transmission time in the range of 0 to 63. It can be used as a TAC value for conveying information (TA).

For reference, the aforementioned initial two bits are TAG id for distinguishing between Primary Component Carrier (PCC) and Secondary Component Carrier (SCC) in relation to the frequency aggregation (Carrier Aggregation) technology as shown in FIG. Can be used as.

Above, the description of the transmission time information TA is finished, and the description of the selection unit 12, which is a configuration of the cell control apparatus 10, will be continued.

The selection unit 12 performs a function of selecting a target small cell.

More specifically, when the location of the terminal (UE#0) connected to the macro cell is confirmed, the selection unit 12 is a terminal (ie, a plurality of small cells SC11, SC12, S14, SC15) located in an inactive state in the macro cell. A small cell (eg, SC12) adjacent to the location of UE#0) is selected as a target small cell for handing over the UE (UE#0).

At this time, the selection unit 12 includes a value of the transmission time information (TA) of the terminal (UE#0) indicating the location of the terminal (UE#0) in the macro cell, and a plurality of small cells (SC11, SC12, S14, SC15). ) It is possible to select a target small cell adjacent to the location of the terminal UE#0 through a method of comparing the values of the transmission time information TA mapped to each.

To this end, each of the plurality of small cells (SC11, SC12, S14, SC15) has a minimum transmission time information (TA) having different values depending on the distance from the cell control device 10 as shown in FIG. It should be mapped even approximately.

The mapping of the transmission time information (TA) for each of the plurality of small cells (SC11, SC12, S14, SC15) is performed, for example, the border area of each small cell, and the corresponding transmission distance from the cell control device 10 This may be achieved through a method of designating a value of the viewpoint information TA.

Here, when the terminal (UE#0) first accesses the small cell (SC12), the value of the transmission time information (TA) of the terminal (UE#0) may be determined as TA=31, and then, the terminal (UE# When 0) moves in the direction of the small cells SC14 and SC15 and the distance between the UE#0 and the cell control device 10 increases, the value of the transmission time information TA of the UE#0 is, for example , TA=32, 33, 34, etc., and on the contrary, when the distance between the terminal (UE#0) and the cell control device 10 becomes close, the transmission time information (TA) of the terminal (UE#0) It can be expected that the value of can be reduced to, for example, TA=30, 29, 28, and the like.

As a result, the selection unit 12 includes a value of the transmission time information TA of the terminal (UE#0) indicating the location of the terminal (UE#0) in the macro cell, and a plurality of small cells (SC11, SC12, S14, SC15). ) Compare the values of transmission time information (TA) mapped to each, and as a result of the comparison, a specific small cell (SC12) whose value is identical or whose value is less than a threshold value is adjacent to the location of the terminal (UE#0) in the macro cell. It can be selected as a target small cell.

On the other hand, it may be assumed that after the terminal UE#0 is connected to the small cell SC11, it is handed over to the macro cell as it moves to the boundary area between the small cell SC11 and the small cell SC12.

In this case, the location of the terminal (UE#0) in the macro cell corresponds to the boundary area between the small cell (SC11) and the small cell (SC12), and the terminal (UE#0) can be handed over within the macro cell. It can be expected that the target small cell may be selected as a small cell SC11 and a small cell SC12.

However, in the case of the small cell (SC12), the terminal (UE#0) is reconnected in consideration of the direction of movement of the terminal (UE#0) because it is a small cell that was accessed before the terminal (UE#0) was handed over to the macro cell. Since the probability is low, it may be excluded in the selection of the target small cell.

The control unit 13 performs a function of handing over the terminal to the target small cell.

More specifically, when the selection of the target small cell is completed, the controller 13 controls the terminal UE#0 to be handed over to the small cell (eg, SC12) selected as the target small cell.

At this time, the control unit 130 switches only the small cell (eg, SC12) selected as the target small cell among a plurality of small cells (SC11, SC12, S14, SC15) located in the macro cell to the active state, thereby making the terminal connected to the macro cell ( UE#0) can be handed over to a small cell (e.g., SC12) that has been converted to an active state, or a new terminal can be reconnected to a small cell (e.g., SC12) that has been converted to an active state. I can.

In this regard, the terminal (UE#0) compares the wireless environment of the macro cell with the wireless environment of the small cell (eg, SC 12) that has been switched to the activated state. If it is better than the wireless environment of the macro cell, handover is performed from the macro cell to the small cell SC 12.

If the terminal (UE#0) is not connected (handover) until a certain time elapses from the time when the small cell (SC 12) is switched to the active state, the small cell switched to the active state (e.g., SC 12 ) Will of course return its state to the inactive state to minimize power consumption.

Hereinafter, the second switching method described above on the premise of the wireless environment shown in FIG. 7 (small cells SC11, SC12, S14, and SC15) in an inactive state according to the control of the cell controller 10 to aid understanding of the description. A method of uniformly switching to this activated state) and a method of converting only a target small cell adjacent to a terminal to an activated state (hereinafter referred to as'third switching method') according to an embodiment of the present invention. I will do it.

7 shows a small cell SC11 to which a first terminal UE#1 is connected among a plurality of small cells SC11, SC12, S14, and SC15 located in a macro cell, and a second terminal UE#2. It shows the state in which the remaining small cells (SC12, S14, SC15) except the connected small cells (SC15) are converted to non-combination state, and a macro cell and a number of small cells (SC11, SC12, S14, SC15) ) Is premised to use different frequency bands.

Here, the first terminal (UE#1) has a fixed position in the small cell (SC11), and the second terminal (UE#2) follows the movement path (SC15 -> SC14 -> SC12) shown by arrows. While moving, it is additionally premised to continuously perform a download operation through a downlink shared channel (PDSCH).

First, a case in which the wireless environment shown in FIG. 7 follows the second switching method will be described.

Initially, the remaining small cells (SC12, S14, SC15) except for the small cell (SC15) to which the second terminal (UE#2) is connected are in a state of being switched to the inactive state, so the connection of the first terminal (UE#1) Accordingly, interference due to transmission of the reference signal CRS is not generated for the small cell SC11 in the active state.

However, in the active small cell (SC11), interference due to transmission of the reference signal (CRS) from the inactive small cells (SC12, S14, SC15) does not occur, while the second terminal (UE#2) is downloaded. The influence of interference by operation exists, because all of the small cells SC11, SC12, S14, and SC15 use the same frequency band.

Thereafter, when the second terminal UE#2 leaves the small cell SC15 and is handed over to the macro cell, the remaining small cells SC12 except for the small cell SC15 to which the second terminal UE#2 was previously connected. , S14) is switched to the activated state by the control according to the second switching method in the cell control device 10.

At this time, in the small cell SC11 to which the first terminal (UE#1) is connected, the second terminal (UE#2) is handed over to a macro cell using a different frequency band, so that the second terminal (UE#2) is downloaded. While the effect of the interference by the operation disappears, the interference caused by the transmission of the reference signal (CRS) from the small cells SC12 and S14 converted to the active state is affected.

Subsequently, the second terminal (UE#2) is handed over to the small cell (S14) that has been converted to the active state according to the movement path. At this time, the second terminal (S) is between the small cell (SC14) and the small cell (SC11). Interference occurs due to the download operation of UE#2), but it can be expected that the magnitude of the interference is not large due to the long distance between each other.

On the other hand, in the case of the small cell SC12 that has been converted to the active state together with the small cell SC14, it returns to the inactive state after a certain period of time due to the non-connection of the second terminal UE#2.

Further, when the second terminal UE#2 leaves the small cell SC14 and is handed over to a macro cell, the remaining small cells SC12 except for the small cell SC14 to which the second terminal UE#2 was previously connected. , SC15 is switched to the activated state by the control according to the second switching method in the cell controller 10.

At this time, in the small cell SC11 to which the first terminal (UE#1) is connected, the second terminal (UE#2) is handed over to a macro cell using a different frequency band, so that the second terminal (UE#2) is downloaded. While the influence of the interference by the operation disappears, the interference caused by the transmission of the reference signal (CRS) from the small cells SC12 and S15 converted to the active state is again affected.

The effect of such interference is that after the second terminal (UE#2) is finally handed over to the small cell (SC12) along the movement path, the small cell (SC15) that is switched to the active state together with the small cell (SC12) is constant. It can be reduced when it transitions to an inactive state over time.

Hereinafter, a case in which the wireless environment shown in FIG. 7 follows the third switching method will be described.

Initially, when the second terminal (UE#2) leaves the small cell SC15 and is handed over to the macro cell, it is not necessary to switch all of the small cells SC12 and S14 to the active state as in the previous second switching method. , Only the small cell S14 adjacent to the location of the second terminal UE#2 is switched to the active state.

In this case, in the case of the small cell SC12 that is not adjacent to the location of the second terminal UE#2, power consumption can be minimized as the inactive state is maintained unlike in the second switching method.

Accordingly, in the small cell SC11 to which the first terminal (UE#1) is connected, the second terminal (UE#2) is handed over to a macro cell using a different frequency band, so that the second terminal (UE#2) is downloaded. The effect of interference by the operation disappears, and only the interference caused by the transmission of the reference signal (CRS) from the small cell S14 converted to the active state is affected.

Subsequently, the second terminal (UE#2) is handed over to the small cell (S14) that has been converted to the active state according to the movement path. At this time, the second terminal (S) is between the small cell (SC14) and the small cell (SC11). Interference occurs due to the download operation of UE#2), but it can be expected that the magnitude of the interference is not large due to the long distance between each other.

Furthermore, when the second terminal (UE#2) leaves the small cell SC14 and is handed over to the macro cell, it is not necessary to switch all of the small cells SC12 and SC15 to the active state as in the previous second switching method. , Only the small cell S12 adjacent to the location of the second terminal UE#2 is switched to the active state.

In this case, in the case of the small cell SC15 that is not adjacent to the location of the second terminal UE#2, unlike in the second switching method, since the inactive state is maintained, power consumption can be minimized.

Accordingly, in the small cell SC11 to which the first terminal (UE#1) is connected, the second terminal (UE#2) is handed over to a macro cell using a different frequency band, so that the second terminal (UE#2) is downloaded. It can be seen that the effect of interference by the operation disappears, and only the interference caused by the transmission of the reference signal (CRS) from the small cell SC12 converted to the active state is affected.

As described above, according to the cell control apparatus 10 according to an embodiment of the present invention, in a wireless environment in which a plurality of small cells in a macro cell are built, adjacent to a terminal among a plurality of small cells in an inactive state As the small cell not adjacent to the terminal is prevented from being unnecessarily switched to the activated state by inducing handover of the terminal connected to the macro cell by switching only the located small cell to the active state, or by inducing the reconnection of a new terminal, It can be seen that the effect of minimizing the power consumption of the small cell due to the elimination of interference between small cells and switching to the active state is achieved.

Hereinafter, an operation flow in the cell control apparatus 10 according to an embodiment of the present invention will be described with reference to FIG. 8.

8 is a schematic flowchart illustrating an operation flow of the cell control device 10 according to an embodiment of the present invention.

As shown in FIG. 8, first, the verification unit 11 is connected to a macro cell according to the deactivation state of each of the plurality of small cells SC11, SC12, S14, SC15 according to steps'S10' to'S30'. Check the location of the terminal (UE#0).

In this way, checking of the terminal (UE#0) connected to the macro cell is for handing over the terminal (UE#0) to a specific small cell adjacent to the current location of the terminal (UE#0) in the macro cell. #0) This can be done only when the number of terminals (traffic amount) connected to the macro cell is greater than or equal to the threshold value according to the connection.

At this time, the verification unit 11 may check the location of the UE #0 in the macro cell through a method of checking the transmission timing information (TA) of the UE#0.

In this regard, the verification unit 11 checks the value of the transmission time information (TA) of the terminal (UE#0) connected to the macro cell, and converts the confirmed value into units of'km' or'msec', It is possible to directly measure the location of the UE (UE#) in the macro cell.

Furthermore, when the location of the terminal (UE#0) connected to the macro cell through step'S30' is identified, the selection unit 12 includes a plurality of small cells (SC11) located in the inactive state in the macro cell according to step'S40'. , SC12, S14, SC15), a small cell (eg, SC12) adjacent to the location of the UE #0 is selected as a target small cell for handing over the UE #0.

At this time, the selection unit 12 includes a value of the transmission time information (TA) of the terminal (UE#0) indicating the location of the terminal (UE#0) in the macro cell, and a plurality of small cells (SC11, SC12, S14, SC15). ) It is possible to select a target small cell adjacent to the location of the terminal UE#0 through a method of comparing the values of the transmission time information TA mapped to each.

To this end, each of the plurality of small cells (SC11, SC12, S14, SC15) has a minimum transmission time information (TA) having different values depending on the distance from the cell control device 10 as shown in FIG. 3, for example. It should be mapped even approximately.

The mapping of the transmission time information (TA) for each of the plurality of small cells (SC11, SC12, S14, SC15) is performed, for example, the border area of each small cell, and the corresponding transmission distance from the cell control device 10 This may be achieved through a method of designating a value of the viewpoint information TA.

As a result, the selection unit 12 includes a value of the transmission time information TA of the terminal (UE#0) indicating the location of the terminal (UE#0) in the macro cell, and a plurality of small cells (SC11, SC12, S14, SC15). ) Compare the values of transmission time information (TA) mapped to each, and as a result of the comparison, a specific small cell (SC12) whose value is identical or whose value is less than a threshold value is adjacent to the location of the terminal (UE#0) in the macro cell. It can be selected as a target small cell.

Thereafter, when the selection of the target small cell is completed through step'S40', the control unit 13 may hand over the terminal (UE#0) to the small cell (eg, SC12) selected as the target small cell according to step'S50'. To be controlled.

At this time, the control unit 130 switches only the small cell (eg, SC12) selected as the target small cell among a plurality of small cells (SC11, SC12, S14, SC15) located in the macro cell to the active state, thereby making the terminal connected to the macro cell ( UE#0) can be handed over to a small cell (e.g., SC12) that has been converted to an active state, or a new terminal can be reconnected to a small cell (e.g., SC12) that has been converted to an active state. I can.

In this regard, the terminal (UE#0) compares the wireless environment of the macro cell with the wireless environment of the small cell (eg, SC 12) that has been switched to the activated state. If it is better than the wireless environment of the macro cell, handover is performed from the macro cell to the small cell SC 12.

If the terminal (UE#0) is not connected (handover) until a certain time elapses from the time when the small cell (SC 12) is switched to the active state, the small cell switched to the active state (e.g., SC 12 ) Will of course return its state to the inactive state to minimize power consumption.

As described above, according to the operation flow of the cell control apparatus 10 according to an embodiment of the present invention, in a wireless environment in which a plurality of small cells in a macro cell are established, among a plurality of small cells in an inactive state Small cells not adjacent to the terminal are unnecessarily switched to the active state by inducing handover of the terminal connected to the macro cell by switching to the active state, or by inducing the reconnection of a new terminal. As it is prevented, it can be seen that the effect of minimizing power consumption of the small cell due to the elimination of interference between the small cells and switching to the active state is achieved.

Meanwhile, the steps of the method or algorithm described in connection with the embodiments presented herein may be directly implemented in hardware or implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded in the medium may be specially designed and configured for the present invention, or may be known and usable to those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. -A hardware device specially configured to store and execute program instructions such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of the program instructions include not only machine language codes such as those produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The above-described hardware device may be configured to operate as one or more software modules to perform the operation of the present invention, and vice versa.

Although the present invention has been described in detail with reference to preferred embodiments so far, the present invention is not limited to the above-described embodiments, and the technical field to which the present invention belongs without departing from the gist of the present invention claimed in the following claims. Anyone of ordinary skill in the art will say that the technical idea of the present invention extends to the range in which various modifications or modifications are possible.

According to a cell control apparatus and a cell control method according to the present invention, in a wireless environment in which a plurality of small cells in a macro cell are established, only a small cell located adjacent to a terminal among a plurality of small cells in an inactive state is switched to an active state to In that it can induce handover of a terminal connected to a cell or induce reconnection of a new terminal, as it exceeds the limitations of the existing technology, it is not only the use of the related technology, but the marketing or sales of the applied device. It is an invention that has industrial applicability because it has sufficient possibilities and can be implemented clearly in reality.

10: cell control device
11: confirmation section 12: selection section
13: control unit

Claims (13)

A verification unit for confirming the location of the terminal in the macro cell from a transmission timing information (TA) value of a terminal connected to the macro cell in a wireless environment in which a plurality of small cells are located in the macro cell;
For each of the plurality of small cells, a target small cell in an inactive state at the location of the terminal among the plurality of small cells is determined based on a result of mapping the transmission time information value in the macro cell according to the position in the macro cell. A selection unit to select; And
And a control unit for converting the target small cell to an activated state so that the terminal can be handed over to the target small cell, or a new terminal can be reconnected to the target small cell,
The selection unit,
Among the plurality of small cells, it is confirmed that there are a first small cell and a second small cell in an inactive state related to the location of the terminal, and the terminal is handed over from the second small cell and connected to the macro cell. If yes, the cell control device, characterized in that selecting only the first small cell as the target small cell. delete delete The method of claim 1,
The target small cell,
A cell control apparatus, characterized in that, among the plurality of small cells, transmission time information having the same value as the transmission time information of the terminal is mapped, or a transmission time information value in which a difference between the transmission time information of the terminal is less than or equal to a threshold is mapped. . delete The method of claim 1,
The confirmation unit,
The cell control apparatus, characterized in that, only when the traffic volume of the macro cell according to the access of the terminal is greater than or equal to a threshold value, the location of the terminal in the macro cell is checked. The method of claim 1,
The terminal,
And handover to the target small cell only when it is determined that the quality measurement value related to the wireless environment in the target small cell is greater than a threshold value than the quality measurement value related to the wireless environment in the macro cell. The method of claim 1,
The target small cell,
When the terminal is not connected from a time point when the terminal is switched to the activated state until a threshold time elapses, the cell control apparatus is returned to a deactivated state. A confirmation step in which the cell control device checks the location of the terminal in the macro cell from the transmission timing information (TA) value of the terminal connected to the macro cell in a wireless environment where a plurality of small cells are located in the macro cell ;
For each of the plurality of small cells, a target small cell in an inactive state at the location of the terminal among the plurality of small cells is determined based on a result of mapping the transmission time information value in the macro cell according to the position in the macro cell. A selection step of selecting; And
The cell control apparatus includes a control step of switching the target small cell to an activated state so that the terminal can be handed over to the target small cell, or a new terminal can be reconnected to the target small cell,
The selection step,
Among the plurality of small cells, it is confirmed that there are a first small cell and a second small cell in an inactive state related to the location of the terminal, and the terminal is handed over from the second small cell and connected to the macro cell. If yes, the cell control method, characterized in that selecting only the first small cell as the target small cell. delete delete The method of claim 9,
The target small cell,
A cell control method, characterized in that, among the plurality of small cells, transmission time information having the same value as the transmission time information of the terminal is mapped, or a transmission time information value in which a difference between the transmission time information of the terminal is less than or equal to a threshold is mapped. . delete

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