KR101873552B1 - Method and Apparatus for Interference Control in Heterogeneous Networks - Google Patents

Abstract

A cell interference control apparatus is disclosed. The apparatus includes a neighboring cell receiving unit for determining a first index of a beam corresponding to a signal received from a neighboring cell and a second index of a beam corresponding to a signal received from a user equipment And an interference manager for performing interference control that may occur between the neighboring cell and the UE based on the comparison result.

Description

TECHNICAL FIELD The present invention relates to an apparatus and method for controlling interference in a HetNet environment,

The present invention relates to interference management of a device having multiple antennas in a wireless communication environment in which macro cells and small cells are mixed.

The existing wireless communication environment consists of macrocells with high transmission power and wide coverage. In recent years, small cells having the same frequency as the macro cell and having a transmission power of less than 10 W per antenna and a relatively narrow coverage are supplementing the shaded area of the base station corresponding to the macro cell in a home, company, or public place Respectively. In recent years, there has been a tendency to use small-sized base stations so as to develop the concept of eliminating shaded areas, to prevent network overload and to provide transmission capacity independently.

Small cells are located within macro cell coverage, and many small cells exist adjacent to each other in the urban environment where the population is large. In such an environment, interference occurs because signals transmitted to peripheral base stations affect small cell coverage. Without interference management, the transmission capacity of small cells can be limited.

The present invention relates to a device for facilitating interference management in a small cell when a small cell is equipped with a network monitoring mode (NMM) function, which is a function of periodically receiving peripheral cell signals located nearby and acquiring information on neighboring cells, Method.

A cell interference control apparatus according to an exemplary embodiment of the present invention includes a neighbor cell receiver for determining a first index of a beam corresponding to a signal received from a neighbor cell, 2 index and the first index, and performs an interference control that may occur between the neighboring cell and the UE based on the comparison result.

Also, a method for controlling a cell interference of an interference control apparatus according to an embodiment of the present invention includes: receiving a signal from a neighboring cell; determining a first index of a beam corresponding to a signal received from the neighboring cell among the plurality of beams; Determining a second index of a beam corresponding to a signal received from the UE, comparing the first index with the second index, and comparing the first index with the second index based on the result of the comparison, And performing an interference control that may occur.

When a small cell is equipped with a network monitoring mode (NMM) function, which is a function of periodically receiving peripheral cell signals located nearby and acquiring information on neighboring cells, the frequency, timing, RSRP Received Power, Direction Information, Master Information Block (MIB), and System Information Block (SIB) messages as information for interference management, thereby facilitating interference management in small cells.

1 shows a network environment in which a macro cell and a small cell according to the present invention are arranged together.
2A shows an example of the direction of a signal transmitted by a macro cell and a plurality of other small cells surrounding one small cell according to the present invention.
2B shows another example of the direction of a signal transmitted by a macro cell and a plurality of other small cells surrounding a small cell according to the present invention.
3 shows an apparatus for acquiring information on neighboring cells according to the present invention.
Figure 4 shows a specific example of an apparatus according to the invention.
5 shows a flow diagram of an operation for receiving neighboring cell information in an apparatus according to the present invention.
6 shows a flow chart of operations for performing interference management in an apparatus according to the present invention.

Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Note that, in the drawings, the same components are denoted by the same reference symbols as possible. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted. In other words, it should be noted that only parts necessary for understanding the operation according to the embodiment of the present invention will be described, and descriptions of other parts will be omitted so as not to disturb the gist of the present invention.

1 shows a network environment in which a macro cell and a small cell according to the present invention are arranged together.

Referring to FIG. 1, a plurality of small cells # 1 to # 4 are located within a coverage of a macro cell. Typically, the coverage of a macrocell is about 35 km in radius, and is circular around the base station of the macrocell on the plane. However, in actuality, it may be a polygonal (usually hexagonal) shape depending on the divisional adjustment according to the intensity of the radio wave with the adjacent cell. The coverage of the macro cell shown in FIG. 1 is an exemplary one for convenience of explanation.

The coverage of the macrocell may include a plurality of small cells (small cells). A small cell may correspond to a small base station having a relatively low transmission power and a narrow coverage, unlike a macro cell having a high transmission power and a wide coverage. In general, a base station device having an output power of 10 W or less per antenna, a pico cell, a femto cell, or a micro cell may be included in a small cell referred to in this document.

The embodiments described in this document can be applied in a situation where various small / large numbers of small cells are mixed in the coverage of the macro cell described above, for example, in a HetNet (Heterogeneous Network) environment.

In the following description, a cell and a base station may be used in combination. For example, the description of a specific cell can be understood as a base station, a base station device, or a base station system that manages a specific cell.

2A shows an example of the direction of a signal transmitted by a macro cell and a plurality of other small cells surrounding one small cell according to the present invention. 2B shows another example of the direction of a signal transmitted by a macro cell and a plurality of other small cells surrounding a small cell.

Referring to FIG. 2A, directions of signals of macro cells and small cells # 1 to # 3 received by small cell # 4 are shown. For example, in the case where the small cell # 4 can determine the direction of the signal in 12 directions (10 degrees per direction) in the range between -60 degrees and +60 degrees, the macro cell, the small cell # 1 (# 4), the sixth (# 5), the seventh (# 6), and the twelfth (# 11) directions, respectively, of the small cell # 2 and the small cell # . Thus, signals of neighboring cells that can be received by the small cell can be appropriately distributed apart.

However, in the example of FIG. 2B, it may happen that signals of peripheral cells are driven in a specific direction. For example, signals from the macro cell, the small cell # 1, the small cell # 2, and the small cell # 3 can be received concentrating on the fifth (# 4) and the sixth (# 5). Since the small cell and the macro cell use signals of the same frequency band, the interference of the signal may occur to a large extent in the case of FIG. 2B as compared with the case of FIG. In other words, direction information of a received signal that can be received by a small cell can play an important role in interference management.

3 shows an apparatus for acquiring information on neighboring cells according to the present invention. The apparatus 300 shown in FIG. 3 can be understood as a system / apparatus provided in a base station or a base station corresponding to one cell.

Referring to FIG. 3, the apparatus 300 may perform an NMM function to periodically receive surrounding cell signals located nearby to acquire information on neighboring cells. The apparatus 300 may include multiple antennas (e.g., P antennas from ANT 1 to ANT P), an RF / IF receiver 310, a neighboring cell receiver 320, and a neighboring cell information manager 330.

The apparatus 300 may include a plurality of antennas, e.g., ANT 1 to ANT P. Each of the antennas can be utilized to find an index of an antenna beam that is oriented in a specific direction. For example, if the device 300 includes P antennas and the spacing of each antenna is d, the device 300 divides 12 spaces between -60 degrees and +60 degrees into 12 beams, It is possible to judge the direction of the received signal by judging from which of the 12 beams the received signal has the largest power. The array response vector representing the beam in each direction can be expressed as follows when constituting B beams between -60 degrees and +60 degrees.

here,

In addition, the apparatus 300 may include an RF / IF receiving unit 210 for receiving an RF (Radio Frequency) signal received from an antenna and converting the RF signal into a base band. The RF / IF receiver 210 may convert the RF signal to an intermediate frequency (IF) and then convert the IF signal to a low frequency baseband signal in order to improve sensitivity or stability . The RF / IF receiver 210 can be understood simply as an " RF receiver " in various embodiments, and a configuration for converting a carrier wave into an IF can be omitted. Also, in some embodiments, an " antenna " may include circuitry, modules, amplifiers, filters, etc. for transmitting and receiving signals through the antenna radiator and emitter. In other words, the antennas ANT1 to ANT P and the RF / IF receiver 310 may be collectively referred to as an "antenna" or an "RF receiver".

The apparatus 300 may include a neighboring cell receiving unit 320. The neighboring cell receiving unit 320 may receive information about a cell located around a cell managed by the device 300 (or managed by the base station corresponding to the device 300) and / or a macro cell to which the device managed by the device 300 belongs. As used herein, the term " surrounding cell " may be understood to include other cells located in the vicinity of the cell and macrocells including the cell. The neighboring cell receiving unit 320 may determine a beam corresponding to a signal received from neighboring cells based on information provided from the RF / IF receiving unit 310. For example, it is possible to determine through which of the N beams the signal received from any one of the plurality of antennas included in the apparatus 300 corresponds to which beam (which beam is the strongest signal) through the neighboring cell receiving unit 320 have. The detailed configuration of the neighboring cell receiving unit 320 will be described with reference to FIG.

The device 300 may further include a neighboring cell information management unit 330. The neighboring cell information management unit 330 may be referred to simply as a " management unit " or as an " information management unit ", an " interference management unit " In various embodiments, the device 300 may include a separate hardware configuration based on the functionality being performed. For example, the device 300 may include an information management unit for managing information on neighboring cells and an interference management unit for managing interference that may occur between neighboring cells and UEs (User Equipments) have. However, in other embodiments, the device 300 may include a control / control module that can integrate or perform all of its functions. In this document, for convenience of description, the peripheral cell information management unit 330 performs the various management / control functions described above, but the configuration of the device 300 is not limited thereto.

Figure 4 shows a specific example of an apparatus according to the invention.

Referring to FIG. 4, the apparatus 400 may include an RF receiver 410, a neighboring cell receiver 420, and a manager 430. Device 400 may correspond to device 300 described above with reference to FIG. For example, the RF receiving unit 410 may correspond to the RF / IF receiving unit 310, the neighboring cell receiving unit 420 may correspond to the neighboring cell receiving unit 320, and the managing unit 430 may correspond to the neighboring cell information managing unit 330. Hereinafter, the description of the configuration that can be associated with the above-described configuration may be omitted.

The neighboring cell receiving unit 420 includes a receiving controller 421, a cell searching unit 422, an OFDM demodulator (Orthogonal Frequency Division Multiplexing Modulator) 423, a CRS channel-specific reference signal channel estimating unit 424, an RSRP / A signal received power / direction estimation unit 425, and a data / control channel demodulator 426.

The reception controller 421 can take charge of the overall control of the peripheral cell receiver 420. Also, the reception controller 421 can control signal reception using an antenna connected to the RF receiver 410 or the RF receiver 410. The cell searcher 422 can perform cell search based on the control of the reception controller 421. [ The OFDM demodulator 423 and the CRS channel estimator 424 may receive the CRS to determine whether there is meaningful (valid) neighboring cell information from the cell search result of the cell searcher 422. The RSRP / direction estimator 425 can calculate the RSRP and estimate the reception direction using the estimation result of the CRS channel estimator 424. In addition, the data / control channel demodulator 426 may receive MIB (Master Information Block) and SI (System Information) messages when the RSRP exceeds the threshold value.

Hereinafter, a method of receiving neighboring cell information using the apparatus 400 of FIG. 4 will be described with reference to FIG.

5 shows an operation for receiving neighbor cell information in an apparatus according to the present invention. 5 is an example corresponding to a LTE (Long Term Evolution) based wireless communication system.

When the neighbor cell reception mode is started in operation 501, the device 400 can provide configuration information for reception of a neighboring cell to the reception controller 421 in operation 503. [ For example, the management unit 430 controls the reception controller 421 to control the frequency of the RF receiver 410, the AGC level (Automatic Gain Control level), the initial timing of the cell receiver 420, the threshold value TH1 ), An RSRP threshold value TH2, and the like.

The receiving controller 421 can set the RF receiving unit 410 using the acquired setting information (e.g., frequency, AGC level). In operation 505, the reception controller 421 may start the cell search by driving the cell searcher 422 when the setting of the RF receiver 410 is completed. The cell searcher 422 may receive a Primary Synchronization Signal (PSS) / Secondary Synchronization Signal (SSS) and acquire a PCI (Physical Cell ID), a frequency, a timing, and a correlation value of neighbor cells as a result of the cell search .

If it is determined in operation 507 that the correlation value is greater than the cell search threshold value TH1 set in the management unit 430, the apparatus 400 should receive the CRS to measure the RSRP for neighbor cells. At operation 509, the receive controller 421 may set the frequency / timing of the RF receiver 410 to receive the CRS. In operation 511, the apparatus 400 may receive the CRS through the OFDM demodulator 423 and estimate the CRS channel of the neighboring cell in the CRS channel estimator 424 in accordance with the timing set in operation 509. RSRP / direction estimator 425 may calculate the RSRP of the neighboring cell in operation 513 based on the CRS channel estimation result of operation 511 and estimate the direction of the signal of the neighboring cell.

There may be a method of estimating a direction by obtaining a correlation matrix of a received signal such as MUSIC (MULTI SIIGNAL CLASSIFICATION), ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique), Root-MUSIC, However, according to the present invention, since the spreading angle of the reception angle is large in the surrounding reflector and the indoor environment, the direction estimation can be performed by finding the index of the antenna beam oriented in a specific direction rather than searching for the correct reception angle. For example, as described above with reference to FIG. 3, the apparatus 400 divides a certain angle range into a first number of spaces by using multiple antennas, defines an index corresponding to a first number of beams, You can judge whether you are bringing in big power. For example, if the first number is n, each beam has an index corresponding to 0 to n-1 or 1 to n, and the apparatus 400 determines which beam index the signal received from the neighboring cell corresponds to can do. Specifically, the RSRP / direction estimator 425 calculates a received signal-to-noise ratio (SNR) by multiplying the channel estimation result of operation 511 by the array response vector of each beam described in FIG. 3, The largest beam may report to the receive controller 421 the index of the beam representing the direction information.

If RSRP computed in RSRP / direction estimator 425 exceeds a certain threshold TH2 at operation 515, then at operation 517 device 400 may receive MIB and SI messages via data / control channel demodulator 426. [ During operation 517, channel estimation via CRS channel estimator 424 and direction estimation of neighboring cells via RSRP / direction estimator 425 may continue to be performed at operation 519. In operation 521, when the MIB / SI message is successfully received, the data / control channel demodulator 426 transmits the MIB / SIB message, frequency, timing, RSRP, and direction information (beam index) of the neighbor cell to the management unit 430 As shown in FIG. At operation 525, the neighbor cell reception mode may be terminated.

If the cell search correlation value is less than the cell search threshold at operation 507, the RSRP is less than the RSRP threshold at operation 515, and the MIB / SI message fails to receive at operation 521, , Timing, AGC level, and the like.

6 shows an operation for performing interference management in an apparatus according to the present invention. The apparatus 300, the apparatus 400, or various deformable interference management systems can perform interference management operations through frequency, timing, RSRP, direction (beam index), MIB / SI message, etc. for neighboring cells provided from the neighboring cell receiving unit 420 have. For example, FIG. 6 is an illustration of a process of an interference management operation using a beam index.

In operation 601, the interference management mode may be started. At operation 603, the device 400 may obtain neighbor cell direction information. For example, the state in which the operation 603 is performed may correspond to a state in which the device 400 acquires the neighboring cell direction information through the process of FIG. For example, of the twelve indices between 0 and 11, the macro cell may correspond to index 4, the first small cell 2, the second small cell 3, and the third small cell 9 index.

A UE coupled to a cell managed by the device 400 transmits a demodulation reference signal or a sounding reference signal for channel estimation in an uplink while attempting to access or access the uplink. In operation 605, the apparatus 400 may use this reference signal to determine the beam index of the signal received from the UE, similar to the manner in which the neighboring cell receiver 420 performs in the above-described process.

If the beam index corresponding to an arbitrary cell is a first index and the beam index corresponding to the UE is a second index, the apparatus 400 determines whether the first index and the second index are smaller than the reference value M in operation 607 . In other words, the apparatus 400 can determine the possibility of occurrence of relatively severe signal interference based on whether the signal received from the neighboring cell and the signal received from the UE are close to a certain standard. For example, if the index of the beam corresponding to an arbitrary cell is 3, and the beam index corresponding to the UE is any one of 2 to 4, the apparatus 400 may determine that interference will occur to a large extent . The reference value M varies depending on the angle separated from the space. When the space between -60 degrees and +60 degrees is divided into 12 spaces as described above, M can be set to a value less than 3. If M is 3, in this example, up to 30 degrees of spreading of the signal can be considered.

In operation 607, if the first index and the second index are located within a specified range M, the apparatus 400 may perform interference control using at least one of operations 611, 615, or 617. For example, at operation 609, the device 400 may determine whether neighboring cells and resources can be allocated and allocated to the UE. If divisional allocation is possible, the device 400 may allocate resources to neighboring cells and UEs at operation 611. [ After operation 611 is performed, the apparatus 400 may proceed to operation 613 to perform additional interference control or terminate the interference control.

At operation 613, the device 400 may determine whether the UE supports Interference Rejection Combining (IRC). Device 400 may send an indication (message) to the UE to perform an IRC at operation 615 if the UE supports IRC. Similarly, after operation 613 is performed, the apparatus 400 may proceed to operation 617 to limit the transmission capacity of the UE, or to terminate the interference control.

In this specification, elements represented as means for performing a specific function encompass any way of performing a particular function, and these elements may be implemented as a combination of circuit elements performing a specific function, or software for performing a specific function May include any form of software, including firmware, microcode, etc., coupled with suitable circuitry to perform.

Reference throughout this specification to " one embodiment " of the principles of the invention and various modifications of such expression in connection with this embodiment means that a particular feature, structure, characteristic or the like is included in at least one embodiment of the principles of the invention it means. Thus, the appearances of the phrase " in one embodiment " and any other variation disclosed throughout this specification are not necessarily all referring to the same embodiment.

It is to be understood that all embodiments and conditional statements disclosed herein are intended to assist one skilled in the art to understand the principles and concepts of the present invention to those skilled in the art, It will be understood that the invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (15)

A cell interference control apparatus comprising:
A method of determining a first index corresponding to a beam from which a signal is received from neighboring cells among a plurality of indexes corresponding to the plurality of beams, Cell receiver, and
Comparing a first index corresponding to a beam from which a signal is received from a user equipment (UE) among the plurality of indexes with the first index, and generating interference and an interference management unit that performs interference control. The method according to claim 1,
Wherein the interference management unit is configured to perform the interference control when the first index and the second index are located within a specified range as a result of the comparison. The method according to claim 1,
Wherein the interference management unit is configured to perform the interference control by dividing and allocating resources to the neighboring cell and the UE. The method according to claim 1,
Wherein the interference management unit is configured to check whether the UE is a UE supporting IRC (Interference Rejection Combining), and to transmit a message for performing IRC to the UE. The method according to claim 1,
And the interference management unit is configured to control the transmission capacity of the UE to perform the interference control. The method according to claim 1,
Wherein a plurality of beams having respective indices are set to be arranged at regular intervals within a specified angular range. The method according to claim 1,
Wherein the neighboring cell receiving unit is configured to determine an index corresponding to a beam having the largest power of a signal received from the neighboring cell as the first index. The method according to claim 1,
And an RF / IF receiver for converting a signal received from the antenna into a baseband signal. The method according to claim 1,
Wherein the neighboring cell receiving unit is configured to receive a cell-specific reference (CRS) from the neighbor cell and calculate a reference signal received power (RSRP) to determine the first index. The method of claim 9,
Wherein the neighboring cell receiving unit is configured to receive at least one of a MIB (Master Information Block) or SI (System Information) when the RSRP exceeds a specified threshold value. Receiving signals from neighboring cells,
Determining a first index corresponding to a beam from which a signal is received from a neighboring cell among a plurality of indexes corresponding to the plurality of beams by dividing a range of a predetermined angle at which a signal is received into a plurality of beams and dividing the beam into a plurality of beams, ,
Determining a second index corresponding to a beam from which a signal is received from a user equipment (UE) among the plurality of indexes,
Comparing the first index and the second index, and
And performing an interference control that may occur between the neighboring cell and the UE based on the comparison result. The method of claim 11,
The operation of performing the interference control includes:
And dividing and allocating resources to the neighboring cell and the UE. The method of claim 11,
The operation of performing the interference control includes:
Determining whether the UE is a UE supporting Interference Rejection Combining (IRC), and transmitting a message for performing IRC to the UE. The method of claim 11,
The operation of performing the interference control includes:
And controlling transmission capacity of the UE. The method of claim 11,
Wherein the determining of the first index comprises:
Estimating a CRS channel received from the neighboring cell,
And calculating an RSRP of the neighboring cell based on the estimated CRS channel result.

Images