KR102421507B1 - Method And Apparatus For Transmitting Adaptive CRS For Interference Mitigation - Google Patents

Abstract

Disclosed are a method and apparatus for transmitting an adaptive common reference signal (RSS) for interference suppression.
As a technology for controlling the transmission of a common reference signal (CRS) transmitted from a terminal for interference suppression in the base station, unnecessary interference is prevented by switching the transmission mode of the common reference signal (CRS) in the base station according to the traffic situation of the cell. Provided are an adaptive common reference signal (CRS) transmission method and apparatus for interference suppression to improve downlink transmission speed by suppressing it.

Description

Method and apparatus for transmitting adaptive common reference signal (CRS) for interference suppression {Method And Apparatus For Transmitting Adaptive CRS For Interference Mitigation}

This embodiment relates to an adaptive common reference signal (CRS) transmission method and apparatus for interference suppression.

The content described below merely provides background information related to the present embodiment and does not constitute the prior art.

Long Term Evolution (LTE) is a mobile communication technology based on an Orthogonal Frequency Division Multiplexing (OFDM) technique that divides the entire frequency band into a plurality of 'sub-carriers' with narrow bandwidths. The frame structure of the Frequency Division Duplex (FDD) LTE system consists of repetitions of 'radio frames' having a length of 10 ms. '1 radio frame' is composed of 10 'sub-frames' each having a length of 1 ms. One 'subframe' consists of two 'time slots' each having a length of 0.5 ms. One 'time slot' consists of a group of OFDM symbols of N ^DL _symbols (6 or 7).

The minimum unit of physical resource of LTE having the frame structure as described above is a 'resource element' (RE), which means that one 'subcarrier' is used for one OFDM symbol duration time (Symbol Duration Time). . A collection of 'resource elements (REs)' of N ^RB _SC adjacent 'subcarriers' during '1 time slot' (0.5 ms) (eg, a total of N ^DL _symb × N ^RB _SC 'resource elements (REs)' group) is called a 'resource block' (RB: Resource Block).

A 'Cell-Specific Reference Signal' (CRS) refers to a signal transmitted by a base station to support a channel estimation and demodulation operation in the terminal. 'Common Reference Signal (CRS)' is a 3GPP standard document for LTE physical channel 'TS 36.211' in the cell's 'Physical Layer Cell Identifier' (PCI: Physical Cell ID) and two adjacent ' on the time axis according to the number of base station antenna ports. The location of the 'resource element (RE)' to be used in the 'resource block (RB)' is defined.

1A is a view showing the location of a 'resource element (RE)' occupied by a 'common reference signal (CRS)' in general. 1A is a diagram illustrating an example of a location of a 'resource element (RE)' to which a 'common reference signal (CRS)' should be transmitted when there are two base station antennas according to the number of antennas. As shown in FIG. 1A , the same pattern is repeatedly applied over the entire system bandwidth even on the frequency axis.

In other words, according to the current LTE standard, the 'common reference signal (CRS)' is set to be continuously transmitted repeatedly every 'subframe' over the entire system bandwidth (eg, 20 MHz). However, in LTE, a specific 'resource block (RB)' is not used by any user as a system in which one user is allocated only a part ('resource block (RB)') from the entire frequency and uses it for a certain period of time. Even in this case, there is a problem in that an unnecessary 'common reference signal (CRS)' signal is continuously transmitted. In particular, even when there is no 'active user' in the cell, the 'common reference signal (CRS)' signal is continuously transmitted from the base station to the terminal. When the load of the cell is small due to the transmission of the 'common reference signal (CRS)', the 'common reference signal (CRS)' is the main cause of inter-cell interference. there is

This embodiment is a technique for controlling transmission of a common reference signal (CRS) transmitted from a terminal for interference suppression in a base station, and the base station switches a transmission mode of a common reference signal (CRS) according to a traffic situation of a cell An object of the present invention is to provide an adaptive common reference signal (CRS) transmission method and apparatus for interference suppression capable of improving downlink transmission speed by suppressing unnecessary interference by doing so.

According to an aspect of the present embodiment, a sub-frame check unit for checking a current sub-frame (Sub-Fame); a status check unit for checking whether a terminal in a cell is in a wake-up state in the current subframe; and when the terminal is in the wake-up state, transmits a Cell-Specific Reference Signal (CRS) to the terminal in a full-band mode, and when the terminal is not in the wake-up state, the common reference signal (CRS) is transmitted to the terminal ) to transmit in a narrowband mode, wherein the status check unit includes at least one of information included in the current subframe and whether a section for the terminal to receive a signal in the current subframe is checked. Based on

According to another aspect of the present embodiment, there is provided a method for a base station to adaptively transmit a common reference signal (CRS) for interference suppression, comprising: a frame checking process of checking a current subframe; a status checking process of checking whether the terminal in the cell is in a wake-up state in the current subframe; and transmitting a common reference signal (CRS) to the terminal in full-band mode when the terminal is in the wake-up state based on the confirmation result of the status check process, and when the terminal is not in the wake-up state, the common reference signal (CRS) is transmitted to the terminal and a mode determining process for transmitting a reference signal (CRS) in a narrowband mode, wherein the status checking process includes information included in the current subframe and a section for the terminal to receive a signal in the current subframe. and determining whether the terminal in the cell is in a wake-up state based on at least one of whether the adaptive common reference signal (CRS) transmission method is provided.

As described above, according to the present embodiment, as a technique for controlling transmission of a common reference signal (CRS) transmitted from the base station to the terminal for interference suppression, the base station controls the transmission of the common reference signal (CRS) according to the traffic situation of the cell. By switching the transmission mode, there is an effect of suppressing unnecessary interference to improve the downlink transmission speed.

According to the present embodiment, since the adaptive common reference signal (CRS) transmission technique changes the transmission mode of the common reference signal (CRS) according to the traffic load of the cell, unnecessary common reference signal (CRS) transmission is eliminated. Accordingly, there is an effect that can increase downlink speed by reducing interference between adjacent cells.

In particular, according to this embodiment, in the case of a new transmission mode using a channel state reference signal (CSI-RS) and a demodulation reference signal (DM-RS) standardized in 3GPP, a new transmission mode supporting the new transmission mode The introduction of a terminal is necessary, and there is a constraint that all users must change to a new terminal. However, the common reference signal (CRS) transmission control technique according to the present embodiment has an effect that not only can obtain a similar effect in the current network in which the existing terminal exists, but also can be immediately applied to the current commercial network.

1A is a diagram illustrating a location of a resource element (RE) occupied by a general common reference signal (CRS).
1B is a diagram illustrating a technique for transmitting a common reference signal (CRS).
2A is a diagram illustrating an adaptive common reference signal (CRS) transmission scheme according to the present embodiment.
2B is a diagram illustrating a location of a resource element (RE) occupied by a common reference signal (CRS) when the adaptive common reference signal (CRS) transmission technique according to the present embodiment is used.
3 is a diagram illustrating a monitoring band setting for measuring radio wave quality in a terminal according to the present embodiment.
4 is a diagram illustrating an operation of an adaptive common reference signal (CRS) transmission scheme in an RRC idle state according to the present embodiment.
5 is a diagram illustrating a random access process in a case of switching from an RRC idle state to an RRC connected state according to the present embodiment.
6 is a diagram illustrating an operation of an adaptive common reference signal (CRS) transmission scheme in an RRC connection state according to the present embodiment.
7 is a diagram illustrating sub-frame positions at which MIB and SIB are transmitted according to the present embodiment.
8 is a block diagram schematically showing a base station according to the present embodiment.
9 is a flowchart for explaining a transmission mode selection algorithm of a common reference signal (CRS) in a base station according to the present embodiment.

Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings.

1B is a diagram illustrating a technique for transmitting a common reference signal (CRS) in general.

According to the current LTE standard, the 'common reference signal (CRS)' is set to be continuously transmitted over the entire system bandwidth (eg, 20 MHz) repeatedly in every 'subframe' for each antenna. The repeated transmission of the 'common reference signal (CRS)' is independent of whether or not the corresponding 'resource block (RB)' is actually used.

1B shows a transmission method of a 'common reference signal (CRS)' of an existing LTE base station. As shown in FIG. 1B , a ‘common reference signal (CRS)’ is transmitted to the entire band in all ‘subframes’ regardless of the traffic state of the cell.

As described above, the 'common reference signal (CRS)', which is always transmitted regardless of the load of the cell, is the main cause of unnecessary interference between adjacent cells. As a result of discussion in the 3rd Generation Partnership Project (3GPP) to solve the repeated transmission of the 'common reference signal (CRS)', the channel measurement and demodulation functions in the terminal responsible for the 'common reference signal (CRS)' are separated and responsible are defined as 'Channel State Information-Reference Signal' (CSI-RS) and 'Demodulation-Reference Signal' (DM-RS), which are new reference signals. Since the 'Channel State Reference Signal (CSI-RS)' is only responsible for channel measurement, it is different from the conventional 'Common Reference Signal (CRS)', which is transmitted every 'subframe', such as 10 ms, 20 ms, 40 ms and 80 ms. It is sent only once every long time. The 'demodulation reference signal (DM-RS)' is a reference signal that is actually allocated to each terminal and is transmitted only from the 'resource block (RB)' that is actually used, so that unnecessary interference is not caused.

In particular, LTE Rel. LTE-Advanced Rel in support of up to 4 base station antennas of 8. When extending from 10 to 8 base station antennas to support, the 'common reference signal (CRS)' for the added antenna based on the above description is undefined, and the channel estimation for 8 antennas is a newly defined ' A channel state reference signal (CSI-RS)' must be used. Therefore, in the future, ultimately, the 'common reference signal (CRS)' will be completely removed, the 'channel state reference signal (CSI-RS)' will replace the channel estimation function, and the 'demodulation reference signal (DM-RS)' will replace the demodulation function. It is expected that a new LTE base station will be introduced.

However, in reality, the current LTE base station has no choice but to maintain the existing method of transmitting a 'common reference signal (CRS)' for a considerable period of time. Terminals supporting 'Channel State Reference Signal (CSI-RS)' and 'Demodulation Reference Signal (DM-RS)' do not yet exist in commercial networks, and even if new terminals are released and spread, users with existing terminals are all new. This is because the 'common reference signal (CRS)' must be maintained for backward compatibility until it is replaced with a terminal.

In this embodiment, while maintaining compatibility with existing terminals, the 'common reference signal (CRS)' signal, which is always transmitted regardless of the presence of an 'active user' in a general cell, is changed depending on the situation depending on the presence or absence of an 'active user' in the cell. We present a control technique for adaptively transmitting a 'common reference signal (CRS)' that can be adjusted accordingly to reduce unnecessary inter-cell interference.

The 'common reference signal (CRS)' signal is not only used for users in a cell, but also terminals belonging to a neighboring cell measure the radio wave quality of the cell and, if necessary, the Mobility Management Entity (MME) is also used to command a handover to the cell. do. Therefore, it is necessary to ensure that there is no abnormality in the measurement of radio wave quality of neighboring cell terminals despite the control of transmission of the 'common reference signal (CRS)' signal depending on the presence or absence of an 'active user' in the cell.

In this embodiment, in order to ensure that there is no abnormality when measuring radio wave quality, the band in which the terminal measures radio wave quality is limited to the smallest specific band (eg, 1.4 MHz) among LTE system bandwidths. In this embodiment, the full-band mode (eg, 20 MHz) in which the transmission mode of the 'common reference signal (CRS)' is transmitted in the entire band, and a narrow band in which only a specific band in the middle of the system bandwidth transmits the 'common reference signal (CRS)' The band mode (eg, 1.4 MHz) is divided into two types. In this embodiment, the transmission mode of the 'common reference signal (CRS)' is divided into a full-band mode and a narrow-band mode, and in any case, a 'common reference signal (CRS)' is present in a specific band in the middle, so that the 'common reference signal (CRS)' is present. (CRS)' In spite of transmission control, there is no problem in the measurement of radio wave quality of the terminal.

2A is a diagram illustrating an adaptive common reference signal (CRS) transmission scheme according to the present embodiment.

The technique of adaptively transmitting a new 'common reference signal (CRS)' proposed in this embodiment reduces unnecessary interference between adjacent cells by switching the transmission mode of the 'common reference signal (CRS)' according to the traffic conditions of the cell, thereby reducing the downlink. Link speed can be improved.

In the method of adaptively transmitting the 'common reference signal (CRS)' according to the present embodiment shown in FIG. 2A, the 'common reference signal (CRS) To the terminal 310 by selecting one of the two transmission modes: the entire band mode for transmitting 'and a narrowband mode (for example, 1.4 MHz) in which only a specific band in the middle of the system bandwidth transmits the 'common reference signal (CRS)' send. Hereinafter, for convenience of description, the present embodiment will be described based on an embodiment in which only the middle 1.4 MHz band is used in the narrowband mode.

2B is a diagram illustrating the position of a 'resource element (RE)' occupied by a 'common reference signal (CRS)' when using a technique for adaptively transmitting a 'common reference signal (CRS)' according to the present embodiment.

Figure 2b is an embodiment showing the location of the 'resource element (RE)' used by the 'common reference signal (CRS)' in the remaining 'resource block (RB)' except for the central 1.4 MHz band in the narrowband mode. The important point is that the first three OFDM symbols of the 'subframe' are used as a physical downlink control channel (PDCCH), so even in the narrowband mode, the 'common reference signal (CRS)' is always transmitted, and user data The 'common reference signal (CRS)' is not transmitted in the remaining portion in which is transmitted.

In the 3GPP standard document 'TS 36.331', which defines an RRC (Radio Resource Control) procedure for controlling a radio channel between the terminal 310 and the base station, the terminal 310 determines the propagation quality of the service cell and the adjacent cell. , RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), the 'AllowedMeasBandwidth' field that sets the reference bandwidth when measuring the same band cell among the SIB (System Information Block) used by the base station to broadcast the system setting information It exists in SIB 3 containing information for selection (Intra-Frequency Cell Reselection) and SIB 5 containing information for other band cell selection (Inter-Frequency Cell Reselection). Related contents are defined as in <Table 1>.

3 is a diagram illustrating a monitoring band setting for measuring radio wave quality in a terminal according to the present embodiment.

Even if the narrowband mode is used according to the traffic situation of the cell, the 'AllowedMeasBandwidth = of SIB 3 and SIB 5 = By setting mbw6', the terminal 310 observes only 1.4 MHz (6 RBs) in the middle when measuring RSRP and RSRQ values. The terminal 310 refers to an electronic device that performs voice or data communication via the base station 320 according to a user's key manipulation. The terminal 310 according to this embodiment means an LTE terminal.

The terminal 310 may have two states, an RRC connected state and an RRC idle state, with the base station 320 . A detailed operation of the technique for adaptively transmitting a 'common reference signal (CRS)' will be described according to whether the terminal 310 is in the RRC idle state, is in the transition from the RRC idle state to the connected state, or is in the RRC connected state.

First, in the RRC idle state, the terminal 310 basically performs a discontinuous reception (DRX) operation to save power. However, the terminal 310 turns off the receiving circuit of the terminal 310 except for the 'Paging Occasion', which is periodically woken up (wake-up state) to check whether there is a paging signal from the base station 320. do. Therefore, in the section in which the terminal 310 turns off the receiver, it is clear that it will not be used even if the base station 320 transmits the 'common reference signal (CRS)' to the entire band. A reference signal (CRS)' is transmitted. <Table 2>, <Table 3> in the 3GPP standard TS 36.304, which defines the terminal operation in the RRC idle mode in which a certain terminal 310 wakes up (wake-up state) to receive paging in a certain 'subframe' is defined as

4 is a diagram illustrating an operation of an adaptive common reference signal (CRS) transmission scheme in an RRC idle state according to the present embodiment.

The base station 320 may predict the 'paging time' for each terminal from an International Mobile Subscriber Identity (IMSI) value, which is a unique ID value for each terminal, and Default DRX Cycle T and nB values, which are base station setting parameters. Accordingly, the base station 320 normally performs paging reception in the terminal 310 using the full-band mode in the 'subframe' in which the 'paging time' of the terminals in the cell exists. In addition, in order to correct the malfunction caused by the terminal implementation, it is possible to set the 'paging margin' before and after the 'paging time', so that during the corresponding 'paging margin' period, the 'common reference signal (CRS) )' is sent. 4 is an embodiment of a technique for adaptively transmitting a 'common reference signal (CRS)' in the base station 320 for the terminal in the RRC idle state as described above (T = 128, nB = 1/8T) , 'paging margin' = 2ms before / 1ms after). As shown in FIG. 4 , a paging frame of a specific terminal exists for every 8 System Frame Numbers (SFN), and the same paging frame is used for every 16 UE_IDs.

5 is a diagram illustrating a random access process in a case of switching from an RRC idle state to an RRC connected state according to the present embodiment.

When the terminal 310 in the RRC idle state switches to the RRC connection state and intends to use upload traffic, the terminal 310 transmits an uplink scheduling request (SR) to the base station 320 . The terminal 310 switches from the RRC idle state to the RRC connected state under the control of the base station 320 .

Similarly, when there is downlink traffic to be transmitted to the terminal 310 from the outside, the base station 320 transmits a paging signal to the terminal 310 at the 'paging time' for each terminal in the cell to set the terminal 310 to an RRC idle state. to the RRC connection state. The transition from the RRC idle state to the RRC connected state is performed using a random access process, and starts from the transmission of a random access preamble in the terminal 310, and the base station 320 and the terminal The RRC, which is the radio control channel of 310, is connected and ends. The entire process of random access in LTE is shown in FIG. 5 .

In the base station 320 , for normal data reception in the terminal 310 during the random access process, a 'random access margin' means a predetermined period from the reception of a random access preamble from the terminal 310 . margin) is set. The base station 320 transmits a 'common reference signal (CRS)' in the full-band transmission mode during the set 'random access margin' period. The time it takes to complete the random access process may vary depending on the distance between the corresponding terminal and the base station and the number of terminals simultaneously attempting RRC connection. In the random access process, there is no problem in adaptively transmitting a 'common reference signal (CRS)' by setting a sufficiently long value based on the statistics of the actual random access time required in the commercial network.

6 is a diagram illustrating an operation of an adaptive common reference signal (CRS) transmission scheme in an RRC connection state according to the present embodiment.

The base station 320 may adjust the transmission mode of the 'common reference signal (CRS)' in connection with the connected mode DRX (CDRX) operation in the case of a terminal in a connected state with the RRC. A case in which the base station 320 does not use the 'Short CDRX' and only the 'Long CDRX' (Long CDRX) will be described. The terminal wakes up (wake-up state) every 'Long DRX Cycle' and receives and monitors a signal from the base station 320 as much as the 'On Duration Timer'. The terminal can save power by turning off the RX of the terminal from the end of the 'On Period Timer' to the next 'Long DRX Cycle'. The terminal extends the period of the 'On Duration' by a non-continuous reception (DRX) inactivity timer (Inactivity Timer) if there is traffic from the base station 320 in a specific 'On Period Timer'. Similar to the RRC idle mode, in the section where the terminal turns off the receiver, even if the base station 320 transmits the 'common reference signal (CRS)' to the entire band, it is clear that it will not be used. A common reference signal (CRS)' is transmitted. In addition, in order to correct a malfunction according to the terminal implementation, the base station 320 allows to set the 'On Duration Margin' respectively before and after the On Duration, so that during the corresponding 'On Duration Margin' period, the entire bandwidth Transmits a 'common reference signal (CRS)' in mode. 5 is an embodiment of a technique for adaptively transmitting a 'common reference signal (CRS)' in the base station 320 for a terminal in a connection state with the RRC as described above (Long CDRX Cycle) ) = 40ms, On Duration Timer = 2 ms, CDRX Inactivity Timer = 10 ms). Of course, it can be expanded similarly even if a 'Short CDRX Cycle' is additionally used.

7 is a diagram illustrating subframe positions at which MIB and SIB are transmitted according to the present embodiment.

The base station 320 transmits a master information block (MIB) and a system information block (SIB) to deliver cell configuration information to the terminal 310 . When transmitting the MIB and SIB, the MIB exists only at 1.4 MHz in the middle, so it is irrelevant to the transmission mode adjustment of the 'common reference signal (CRS)', and in the case of other SIBs (eg, SIB 1 to SIB 13), the base station 320 Since the 'subframe' in which the corresponding SIB is transmitted can be accurately identified, the 'common reference signal (CRS)' is transmitted in the full-band mode in the 'subframe' in which the corresponding SIB is present.

7 is a diagram illustrating positions of 'radio frames' and 'subframes' in which MIBs and SIBs exist according to SFN (System Frame Number).

As shown in FIG. 7 , the MIB is transmitted every 'subframe' 0 of every 'wireless frame' from 'SFN 0'. In SIB 1, 5 'subframes' of every 8 'radio frames' (SFN Mod 8 = 0) are transmitted from 'SFN 0', and the same SIB 1 has a different RV (Redundancy Value) for every SFN Mod 2 = 0. is sent All other SIBs are transmitted at the period and position determined from SIB 1.

8 is a block diagram schematically showing a base station according to the present embodiment.

The base station 320 according to the present embodiment includes a frame checker 810 , a status checker 820 , and a mode determiner 830 . Components included in the base station 320 are not necessarily limited thereto.

Each component included in the base station 320 may be connected to a communication path connecting a software module or a hardware module inside the device, so that they can operate organically with each other. These components communicate using one or more communication buses or signal lines. Each component of the base station 320 shown in FIG. 8 means a unit for processing at least one function or operation, and may be implemented as a software module, a hardware module, or a combination of software and hardware.

The frame check unit 810 checks the current sub-frame. The frame check unit 810 checks the number of the sub-frame. The frame check unit 810 checks a number for every sub-frame. When the common reference signal (CRS) is transmitted to the terminal in the cell in the full-band mode or the narrow-band mode by the mode determiner 830, the frame check unit 810 determines the next sub-frame of the current sub-frame number F. Increase or decrease the value by 1 (F = F + 1).

The state check unit 820 checks whether the terminal in the cell is awake (wake-up state) in the current subframe.

Hereinafter, the operation of the status check unit 820 will be described in detail. If the SIB exists in the current subframe, the status check unit 820 checks that the terminal is awake (wake-up state). If the SIB does not exist in the current subframe F, the status check unit 820 sets the number of terminals in the cell to N (N = the number of terminals in the cell), and sets I in the cell to 1 (I = 1) do. The status check unit 820 checks whether the number of terminals in the cell (N) and the number of terminals (I) in the cell are the same value (I = N). If the number of terminals in the cell (N) and the number of terminals (I) in the cell are the same (I = N), the state check unit 820 determines that the terminal is not awake (wake-up state). .

When the paging time or paging margin for the terminal 310 is checked in the current subframe, the status check unit 820 checks that the terminal 310 is awake (wake-up state). In other words, when the number of terminals in the cell (N) and the number of terminals (I) in the cell are not the same (I ≠ N), the status check unit 820 determines the number of terminals (I) in the current subframe (F). Check whether paging timing or paging margin is checked. When the paging time or paging margin for the terminal I is checked in the current subframe F, the status check unit 820 checks that the terminal in the cell is awake (wake-up state).

The status check unit 820 confirms that the terminal 310 is awake (wake-up state) when the random access process for the terminal 310 is in progress or the random access margin is checked in the current subframe. In other words, when the number of terminals in the cell (N) and the number of terminals (I) in the cell are not the same (I ≠ N), the status check unit 720 determines the number of terminals (I) in the current subframe (F). It is checked whether a random access process is in progress or a random access margin is checked. The status check unit 820 confirms that the terminal in the cell is awake (wake-up state) when the random access process for the terminal I is in progress in the current subframe F or the random access margin is checked. .

The status check unit 820 determines that the terminal 310 is awake (wake-up state) when the on-section or on-section margin is checked in a non-continuous reception cycle (DRX Cycle) for the terminal 310 in the current subframe. Check it. In other words, when the paging time or paging margin for the terminal I is not confirmed in the current subframe F, the status check unit 820 is non-consecutive for the terminal I in the current subframe F. It is checked whether the on section or the on section margin is checked in the receive cycle (DRX Cycle).

When the on-interval or on-interval margin is checked in the non-continuous reception cycle for the terminal I in the current subframe F, the status check unit 820 determines that the terminal in the cell wakes up (wake-up). status) is checked.

If the on-interval or on-interval margin is not confirmed in the non-continuous reception cycle for the terminal I in the current subframe F, the base station 320 sets 1 to the terminal I value in the cell. It is set as an increase/decrease value (I = I + 1). After increasing or decreasing the value of I by 1, the status check unit 820 checks whether the number of terminals in the cell (N) and the number of terminals (I) in the cell are the same value (I = N). If the number of terminals in the cell (N) and the number of terminals (I) in the cell are the same (I = N), the state check unit 820 determines that the terminal is not awake (wake-up state). .

The mode determiner 830 transmits the common reference signal CRS to the terminal 310 in the full-band mode when the terminal 310 is awake (wake-up state).

Hereinafter, a process in which the mode determiner 830 operates in the full-band mode will be described in detail. The mode determiner 830 determines that the terminal is awake (wake-up state) when the state check unit 820 determines that the SIB is present in the current subframe, and transmits the common reference signal (CRS) to the full-band mode. It is transmitted to the terminal in the cell. The mode determiner 830 determines the common reference signal CRS in the full-band mode when the state checker 820 determines the paging timing or paging margin for the terminal I in the current subframe F. transmitted to the terminal in The mode determiner 830 determines that the state check unit 820 uses a common reference signal in the full-band mode when a random access process for the terminal I is in progress or a random access margin is checked in the current subframe F. (CRS) is transmitted to the terminal in the cell. When the state check unit 820 checks the on-interval or on-interval margin in the non-continuous reception cycle for the terminal I in the current subframe F, the mode determination unit 830 refers to the common all-band mode. A signal (CRS) is transmitted to the terminal in the cell.

The mode determiner 830 transmits the common reference signal CRS to the terminal 310 in the narrowband mode in the remaining time other than the time when the terminal 310 is awake (wake-up state).

Hereinafter, a process in which the mode determiner 830 operates in the narrowband mode will be described in detail. The mode determination unit 830 sends the common reference signal (CRS) to the terminal 310 when the status check unit 820 determines that the number of terminals in the cell (N) and the number of terminals in the cell (I) are the same (I = N). ) is transmitted in narrowband mode. The number of terminals in a cell (N) increases when a new terminal accesses the corresponding base station, and decreases when moving to an adjacent cell (ie, handover).

The mode determiner 830 improves the downlink transmission speed by matching the non-continuous access mode reception period between terminals within a cell.

9 is a flowchart for explaining a transmission mode selection algorithm of a common reference signal (CRS) in a base station according to the present embodiment.

In an actual cell, since the RRC access terminal and the RRC idle terminal coexist, the base station 320 examines all the above-mentioned conditions for each 'subframe', whether the SIB exists, and for each RRC state of each terminal. If the mode is not suitable for transmitting a 'common reference signal (CRS)', the full-band mode is used. The base station 320 transmits a 'common reference signal (CRS)' by selecting a narrowband mode when all conditions are satisfied. 9 is a flowchart of a transmission mode selection algorithm of a 'common reference signal (CRS)' in the base station 320 as described above.

In addition, in order to improve the performance of the base station 320 that adaptively transmits a 'common reference signal (CRS)' operating as described in FIG. 9, the following may be considered. Since the CDRX function can be operated separately for each terminal, when the CDRX cycle is different for each terminal, there is a problem in that the efficiency of adjusting the transmission mode of the 'common reference signal (CRS)' is lowered. Accordingly, a CDRX Alignment function that allows traffic to be transmitted and RX of terminals simultaneously turned off when a plurality of terminals exist in accordance with the CDRX cycle for each terminal in a cell may be considered.

The base station 320 checks the current subframe (S910). In step S910, the base station 320 checks the number (F) of the subframe. As a result, the base station 320 checks the number F for every subframe.

The base station 320 checks whether the SIB exists in the current subframe (S920). As a result of the check in step S920, if the SIB exists in the current subframe (F), the base station 320 checks that the terminal in the cell is awake (wake-up state) and transmits the common reference signal (CRS) to the cell in the full-band mode. It is transmitted to the terminal within (S922). After performing step S922, the base station 320 increases or decreases 1 (F = F + 1) to the value F, which is the current sub-frame number, in order to check the next sub-frame (S924). The base station 320 returns to step S910 after performing step S924.

As a result of the check in step S920, if the SIB does not exist in the current subframe F, the base station 320 sets the number of terminals in the cell to N (N = the number of terminals in the cell), and sets the terminal I in the cell to 1 Set (I = 1) (S930). The base station 320 checks whether the number of terminals in the cell (N) and the number of terminals (I) in the cell have the same value (I = N) (S932).

As a result of checking in step S932, if the number of terminals in the cell (N) and the terminal (I) in the cell are the same value (I = N), the base station 320 confirms that the terminal is not awake (wake-up state), A common reference signal (CRS) is transmitted to the terminal 310 in the narrowband mode (S934). After performing step S934, the base station 320 increases or decreases 1 (F = F + 1) to the value F, which is the current subframe number, in order to check the next subframe (S924).

As a result of checking in step S932, if the number of terminals in the cell (N) and the number of terminals (I) in the cell are not the same (I ≠ N), the base station 320 transmits the terminal I in the current subframe F. It is checked whether a paging time or a paging margin is checked (S940).

As a result of the check in step S940, if the paging time or paging margin for the terminal I is confirmed in the current subframe F, the base station 320 confirms that the terminal in the cell is awake (wake-up state), The common reference signal (CRS) is transmitted to the terminal in the cell in the band mode (S922).

As a result of the check in step S940, if the paging time or paging margin for the terminal I is not confirmed in the current subframe F, the base station 320 randomizes the terminal I in the current subframe F. It is checked whether an access process is in progress or a random access margin is checked ( S950 ). As a result of checking in step S950, if the random access process for the terminal I in the current subframe F is in progress or the random X margin is not confirmed, the base station 320 controls the terminal I in the current subframe F ), it is checked whether the on-section or the on-section margin is checked in the non-continuous reception cycle (DRX Cycle) (S960).

As a result of the check in step S960, if the on-interval or on-interval margin is confirmed in the non-continuous reception cycle for the terminal I in the current subframe F, the base station 320 indicates that the terminal in the cell is awake (wake-up state). ) and transmits the common reference signal (CRS) to the terminal in the cell in the full-band mode (S922). As a result of checking in step S650, if the on-interval or on-interval margin is not confirmed in the non-continuous reception cycle for the terminal I in the current subframe F, the base station 320 increases or decreases the terminal I value in the cell by 1 It is set to one value (I = I + 1) (S962). The base station 320 returns to step S932 after performing S962.

Although it is described that steps S910 to S962 are sequentially executed in FIG. 9 , the present invention is not limited thereto. In other words, since it may be applicable to changing and executing the steps described in FIG. 9 or executing one or more steps in parallel, FIG. 9 is not limited to a time-series order.

As described above, the method for selecting the transmission mode of the common reference signal (CRS) in the base station according to the present embodiment described in FIG. 9 may be implemented as a program and recorded in a computer-readable recording medium. A program for implementing a method of selecting a transmission mode of a common reference signal (CRS) in a base station according to the present embodiment is recorded and a computer-readable recording medium is any type in which data that can be read by a computer system is stored includes a recorder of

The above description is merely illustrative of the technical idea of this embodiment, and a person skilled in the art to which this embodiment belongs may make various modifications and variations without departing from the essential characteristics of the present embodiment. Accordingly, the present embodiments are intended to explain rather than limit the technical spirit of the present embodiment, and the scope of the technical spirit of the present embodiment is not limited by these embodiments. The protection scope of this embodiment should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present embodiment.

As described above, the present embodiment is applied to the field of controlling the transmission of the common reference signal (CRS) transmitted from the terminal for interference suppression, and the base station transmits the transmission mode of the common reference signal (CRS) according to the traffic situation of the cell. It is a useful invention that produces the effect of improving the downlink transmission speed by suppressing unnecessary interference by switching the

310: terminal 320: base station
810: frame check unit 820: status check unit
830: mode decision unit

Claims (6)

a sub-frame check unit for checking a current sub-frame (Sub-Fame);
a status check unit for checking whether the terminal in the cell is in a wake-up state in the current subframe; and
When the terminal is in the wake-up state, a cell-specific reference signal (CRS) is transmitted to the terminal in the full-band mode, and when the terminal is not in the wake-up state, the common reference signal (CRS) is transmitted to the terminal Including a mode determination unit to transmit in a narrowband mode,
The status check unit,
When the On Duration or On Duration Margin for the connected mode non-continuous reception (Connected Mode DRX, CDRX) of the terminal in the RRC connected (Connected) state is confirmed in the current subframe, the A base station, characterized in that it confirms that the terminal is in a wake-up state. According to claim 1,
The status check unit,
When a system information block (SIB) exists in the current subframe, the base station characterized in that it is confirmed that the terminal is in a wake-up state. According to claim 1,
The status check unit,
The base station, characterized in that when paging timing (Paging Occasion) or paging margin (Paging Margin) for the terminal is checked in the current subframe, it is confirmed that the terminal is in a wake-up state. According to claim 1,
The status check unit,
In the current subframe, when a random access process for the terminal is in progress or a random access margin is confirmed, the base station is characterized in that it is confirmed that the terminal is in a wakeup state. delete A method for a base station to adaptively transmit a common reference signal (CRS) for interference suppression,
a frame checking process of checking the current subframe;
a status checking process of checking whether the terminal in the cell is in a wake-up state in the current subframe; and
When the terminal is in the wake-up state, a common reference signal (CRS) is transmitted to the terminal in full-band mode based on the confirmation result of the status check process, and when the terminal is not in the wake-up state, the common reference signal is transmitted to the terminal Mode determination process to transmit signal (CRS) in narrowband mode
including,
The status check process is
When the On Duration or On Duration Margin for the connected mode discontinuous reception (Connected Mode DRX, CDRX) of the terminal in the RRC connected (Connected) state is confirmed in the current subframe, the An adaptive common reference signal (CRS) transmission method, characterized in that it is confirmed that the terminal is in a wake-up state.

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