KR102117750B1 - Method and system for setting cell coverage based on blockage-aware - Google Patents

Abstract

Provides a method and system for setting obstacle-based cell coverage. The present invention can prevent inter-beam interference emitted from a plurality of base stations by using the characteristics of millimeter waves that are easily blocked by obstacles, and improve the transmission speed. In addition, the base station around the building where multiple users are likely to be densely set the cell coverage only in the direction of the building, so that the load of each base station can be equally adjusted. In addition, by providing a method for determining the size of the cell coverage set by the base station selected in the obstacle direction among the plurality of base stations, it is possible to easily adjust the cell coverage of each base station.

Description

METHOD AND SYSTEM FOR SETTING CELL COVERAGE BASED ON BLOCKAGE-AWARE}

The present invention relates to a cell coverage setting method and system, and more particularly, to an obstacle recognition-based cell coverage setting method and system in a millimeter wave network.

Due to the development of mobile communication technology, various services are provided through mobile devices, but the demand for more various services and high service quality is increasing. Due to this, mobile data usage is rapidly increasing, and it is difficult to satisfy the required service quality with the frequency band used in the existing mobile communication system.

Accordingly, recently, a technique using a millimeter-wave in mobile communication technology has been studied. When a mobile communication system uses millimeter wave, a transmission speed increase of 1000 times can be obtained with a bandwidth of 20 to 100 times larger than that of a conventional mobile communication using a 6 GHz frequency.

However, the millimeter wave has a limitation that a signal is easily blocked by an obstacle such as a human body or a building due to a large attenuation due to path loss due to the characteristics of a high frequency signal. Due to this, there is a disadvantage that the coverage is narrow due to a short distance that an individual base station (BS) can provide a service to a user equipment (UE).

In order to overcome the shortcomings of the mobile communication system using the millimeter wave, a number of small base stations are recently installed, and each of the small base stations applies a beamforming technique to form a narrow beam main lobe, thereby forming a beam. Techniques for improving the reach of are being studied. That is, a method of supplementing the coverage of the small cell by increasing the directivity has been studied. However, such a technique may generate an area overlapping with a beam emitted from an adjacent small base station due to an increase in a beam's reach, and interference may occur. When inter-beam interference occurs, a signal to interference noise ratio (SINR) decreases and communication performance decreases.

If each base station recognizes the mutual state, it is possible to control such as forming a beam or changing a channel so as to avoid inter-beam interference, but for this, a very complex operation is performed with a backhaul capacity for a large amount of information exchange. Requested, there is a limit to apply to a small base station.

Korean Registered Patent No. 10-1675688 (Registered on Nov. 7, 2016)

An object of the present invention is to provide an obstacle recognition-based cell coverage setting method and system capable of preventing inter-beam interference and improving transmission speed by using the characteristics of millimeter waves that are easily blocked by obstacles.

Another object of the present invention is a method and system for establishing a cell coverage based on obstacle recognition that enables a base station adjacent to a building where multiple users are likely to be densely formed to emit and radiate a beam in the direction of the building, so as to equally control the load of each of the plurality of base stations. To provide.

Another object of the present invention is to select a base station to radiate a beam in the direction of the obstacle among a plurality of base stations according to the size of the obstacle and the state of the terminal around the obstacle obstacle recognition base that can determine the width of the beam to be emitted by the selected base station It is to provide a method and system for setting cell coverage.

Cell coverage setting method according to an embodiment of the present invention for achieving the above object in a mobile communication system including a plurality of base stations, using the pre-stored base station position and the location and size information of the obstacle, the plurality of base stations Determining a candidate directional base station included within a predetermined range from the obstacle, and at least one of the candidate directional base stations sets cell coverage in the obstacle direction and performs communication with the user terminal in the set cell coverage And selecting as a directional base station.

The step of determining the candidate directional base station includes setting a directional bias for designating a range to which a beam emitted from the directional base station is radiated among the entire length of the obstacle, and the directional bias from the obstacle among the plurality of base stations. And selecting at least one base station within a corresponding range as a candidate directional base station.

The selecting of the directional base station includes calculating SIR coverage indicating a probability of communication success of the user terminal when all of the at least one candidate directional base station operates as the directional base station, and the SIR coverage is equal to or greater than a preset threshold value. Calculating the optimal directional bias to maximize the transmission speed of the user terminal, calculating each of the candidate directional base stations with a steering angle corresponding to the optimal directional bias, and calculating the steering angle of each candidate directional base station If it is equal to or greater than the set minimum steering angle, it may include selecting the candidate directional base station as a directional base station and setting cell coverage according to the calculated steering angle.

The step of selecting the directional base station may include selecting the candidate directional base station again by changing the directional bias if the SIR coverage is less than a threshold, and if the calculated steering angle is less than the minimum steering angle of at least one candidate directional base station, The method may further include excluding a candidate directional base station having a minimum steering angle from the candidate base station.

A base station that is not selected as the directional base station among the plurality of base stations may be set as an omni-directional base station capable of beamforming in all directions regardless of an obstacle.

In the method of setting the cell coverage based on obstacle recognition in the mobile communication system, the at least one directional base station transmits the reference signal, and the directional base station that receives a pilot signal corresponding to the reference signal from the user terminal communicates with the user terminal. Communicating, receiving an inverse pilot signal transmitted from a user terminal that has not received the reference signal by an omni-directional base station excluding the at least one directional base station among the plurality of base stations, and transmitting the inverse pilot signal The directional base station may further include transmitting an acknowledgment signal to the user terminal, and communicating with the user terminal by an omni-directional base station receiving a pilot signal corresponding to the acknowledgment signal from the user terminal.

The obstacle recognition-based cell coverage setting system according to another embodiment of the present invention for achieving the above object is selected according to the pre-stored base station position and the position and size information of the obstacle among a plurality of base stations, and is arranged within a predetermined range from the obstacle , At least one directional base station that sets cell coverage in the obstacle direction and performs communication with a user terminal within the set cell coverage, and a cell coverage set by the directional base station as a base station excluding the directional base station among the plurality of base stations It may include at least one omni-directional base station for communicating with an external user terminal.

Therefore, the obstacle recognition-based cell coverage setting method and system of the present invention can prevent inter-beam interference emitted from multiple base stations and improve transmission speed by using the characteristics of millimeter waves that are easily blocked by obstacles. In addition, by allowing a base station around a building where multiple users are likely to be concentrated to set cell coverage only in the direction of the building, the load of each base station can be equally adjusted. In addition, among a plurality of base stations, it is possible to easily adjust the cell coverage of each base station by selecting a base station to set cell coverage in an obstacle direction and determining a size of the cell coverage set by the selected base station. In particular, it is possible to provide a cell coverage setting method for improving communication performance by reducing interference and improving transmission speed in an outdoor area of a city center where many buildings are concentrated.

1 and 2 are diagrams for explaining the concept of an obstacle recognition-based cell coverage setting method according to an embodiment of the present invention.
3 to 5 are diagrams illustrating a change in cell coverage according to selection of a directional base station in a method for setting a cell coverage based on obstacle recognition according to an embodiment of the present invention.
6 is a view for explaining the definition of directional bias according to an embodiment of the present invention.
7 shows an example of a directional base station selection area corresponding to a directional bias.
8 shows a method for setting a cell coverage based on obstacle recognition according to an embodiment of the present invention.
9 illustrates a method in which a directional base station and an omni-directional base station set according to an obstacle recognition-based cell coverage setting method according to an embodiment of the present invention communicate with a user terminal.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the contents described in the accompanying drawings, which illustrate preferred embodiments of the present invention.

Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the present invention with reference to the accompanying drawings. However, the present invention can be implemented in various different forms, and is not limited to the described embodiments. And, in order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless otherwise stated. In addition, terms such as "... part", "... group", "module", and "block" described in the specification mean a unit that processes at least one function or operation, which is hardware or software or hardware. And software.

1 and 2 are diagrams for explaining the concept of an obstacle recognition-based cell coverage setting method according to an embodiment of the present invention.

1 and 2 illustrate, for example, a case in which three user terminals UE1, UE2, and UE3 are located in cell coverage of two base stations BS1 and BS2.

The two base stations BS1 and BS2 each transmit a reference signal within within a predetermined cell coverage. Accordingly, each of the three user terminals (UE1, UE2, and UE3) receives a reference signal and determines a base station that has transmitted Reference Signals Received Power (RSRP) from the received reference signal to connect to the determined base station. To send. Then, the base station receiving the connection request message allocates resources such as a channel to the user terminal that has transmitted the connection request message, and then the user terminal to which the resource is allocated can communicate with the corresponding base station.

Referring to FIG. 1, when the first user terminal UE1 communicates through the first base station BS1, while the second user terminal UE2 communicates with the second base station, the first and first terminals Each of the two base stations BS1 and BS2 may form a beam in the direction of the user terminal to facilitate communication with the first and second user terminals UE1 and UE2. That is, the first base station BS1 may form a beam in the direction of the first user terminal UE1, and the second base station BS2 may form a beam in the direction of the second user terminal UE2.

In this case, as shown in FIG. 1, the beam emitted from the first base station BS1 may pass through the first user terminal UE1 and reach the second user terminal UE2. That is, in the position of the second user terminal UE2, the beam emitted from the first base station BS1 and the beam emitted from the second base station BS2 overlap each other, and signal interference occurs. Accordingly, the signal to interference noise ratio (SINR) of the second user terminal UE2 is greatly reduced.

However, as shown in Figure 2, if the cell coverage is limited so that the first base station (BS1) adjacent to the obstacle (Blockage) (BLK) is directed to only the obstacle direction, the first base station (BS1) and the second base station (BS2) An area where the emitted beams overlap each other is not generated, so that interference can be avoided. In addition, because the beam emitted from the first base station BS1 does not transmit the obstacle BLK according to the characteristics of the millimeter wave, interference with the beam emitted from the base station (not shown) disposed opposite the obstacle BLK also Can be avoided.

However, as shown in FIG. 2, when the cell coverage fixed in the obstacle direction of the first base station BS1 is set, the first base station BS1 can communicate with the third user terminal UE3, whereas the 1 Communication with the user terminal UE1 cannot be performed. Therefore, the first and second user terminals UE1 and UE2 must communicate with the second base station BS2, unlike in FIG. 1.

Considering that the reference signal received power (RSRP) with the first base station (BS1) in the first user terminal (UE1) is greater than the RSRP with the second base station (BS2), it may be determined to be inefficient. However, since interference due to the beams emitted from the first and second base stations BS1 and BS2 does not occur, SINR is greatly reduced, and as a result, not only the second user terminal UE2 but also the first user terminal UE1 is more stable. And can provide effective communication.

Meanwhile, as shown in FIG. 2, when the cell coverage of the first base station BS1 is fixed in an obstacle direction, the first base station BS1 is compared to the cell coverage of the second base station BS2 capable of beamforming in all directions. ), the size of the cell coverage becomes very small. That is, a difference in size of cell coverage corresponding to each of the base stations BS1 and BS2 may occur. However, in general, a relatively large number of users are located around obstacles such as buildings, while a relatively small number of users are located in other areas. Therefore, despite the difference in the size of the cell coverage corresponding to each base station (BS1, BS2), each base station (BS1, BS2) can have a rather equal load. That is, the load concentrated on the first base station BS1 can be reduced.

3 to 5 are diagrams illustrating a change in cell coverage according to selection of a directional base station in a method for setting a cell coverage based on obstacle recognition according to an embodiment of the present invention.

3 to 5, for convenience of description, only three base stations BS1 to BS3 are shown, but a plurality of base stations may be arranged.

FIG. 3 shows cell coverage when all base stations BS1 to BS3 operate as omni-directional base stations (O-BS) that communicate with user terminals in all directions, and FIG. 4 is a first base station Cell coverage when (BS1) operates as a directional base station (D-BS) that communicates with a user terminal in the direction of an obstacle. And Figure 5 shows the cell coverage when the first and second base stations (BS1, BS2) operates in conjunction with a directional base station (D-BS) that points the obstacle direction.

First, referring to FIG. 3, since all base stations BS1 to BS3 operate as omni-directional base stations (O-BS), each of a plurality of base stations BS1 to BS3 is a terminal within a cell coverage specified regardless of an obstacle BLK The communication is performed using beamforming. However, at this time, the formed beam may be radiated to the cell coverage of the other base station, which may cause interference with the beam emitted from the other base station.

3 illustrates a case in which the beam emitted from the first base station BS1 reaches the user terminal UE located in the cell coverage of the second base station BS2. In this case, some of the user terminals (UE) of the second base station (BS2) due to the inter-beam interference is significantly reduced SINR, the communication quality is significantly lowered.

In addition, many users are often located around obstacles such as buildings (BLK). In particular, in the case of the outdoors in the city, it is often the case that users are densely located around the building compared to roads or empty spaces. In the present invention, an area in which a large number of users are concentrated within a certain distance (dc) from an obstacle BLK is referred to as a user concentrated area (An), and other areas than a user non-concentrated area (User non- concentrated area) (Ar).

Accordingly, when an obstacle BLK such as a building is disposed in the cell coverage of a specific base station (the first base station BS1 in FIG. 3), the number of user terminals (UEs) that the base station must communicate with is very large compared to other base stations. That is, the load of a particular base station is significantly increased compared to other base stations.

Accordingly, in FIG. 4, the first base station BS1 among the three base stations BS1 to BS3 is selected as a directional base station (D-BS) that only directs the obstacle BLK direction, and the first base station BS1 is the obstacle BLK. Directing in the direction to configure the cell coverage. That is, the first base station BS1 forms the beam only in the direction of the obstacle BLK. Therefore, the first base station BS1 mainly communicates with the user terminal UE in the user concentration area An around the obstacle BLK, and the load is reduced.

In addition, as described above, since the millimeter wave may be blocked by the obstacle BLK, communication with the user terminal UE located in the user concentration area An on one side of the obstacle BLK is mainly performed. No interference is generated with respect to the user terminal UE located in the user concentration area An on the other side of the (BLK). Therefore, it reduces the load and does not generate interference with beams emitted from other base stations.

However, when the first base station BS1 configures the cell by pointing in the direction of the obstacle BLK, the size of the cell coverage of the first base station BS1 is smaller than that of FIG. 3, which causes the user terminal at a specific location to A network coverage hole that does not receive communication service may occur.

Accordingly, in the present invention, by allowing other base stations BS2 and BS3 to expand the cell coverage from the first base station BS1 to the reduced cell coverage, network coverage holes are prevented from occurring. A detailed method for preventing the occurrence of network coverage holes will be described later.

On the other hand, referring to FIG. 4 again, the first base station BS1 is a directional base station (D-BS), even though forming the cell coverage in the direction of the obstacle BLK, the user terminal in the cell coverage of the first base station BS1 ( The number of UEs is higher than that of other base stations (BS2, BS3). That is, it can be seen that the load of the first base station BS1 is still high.

Accordingly, in FIG. 5, not only the first base station BS1 but also the second base station BS2 is selected as a directional base station (D-BS) which is directed in the direction of the obstacle BLK. Therefore, both the first and second base stations BS1 and BS2 form cell coverage in the direction of the obstacle BLK as a directional base station (D-BS).

Since the first and second base stations BS1 and BS2 communicate with the user terminal UE located in the user concentration area An on one side of the obstacle BLK, the load of the first base station BS1 is further increased. It can be alleviated. That is, it is possible to perform load balancing (Load Balancing) to equally adjust the load of each base station.

In this case, as the first and second base stations BS1 and BS2 form the cell coverage in the user concentration area An on one side of the obstacle BLK, the cell coverage may overlap. That is, interference may occur due to overlapping beams. However, the first and second base stations BS1 and BS2 have fixed cell coverage as a directional base station (D-BS), and need not consider interference with other base stations, but only mutual interference. That is, the first and second base stations BS1 and BS2 do not require backhaul capacity or complicated calculation, and can recognize mutual states by exchanging small amounts of information. Therefore, it is possible to form a beam to prevent overlap of beams within overlapped cell coverage, or to prevent interference by adjusting a channel or time.

6 is a view for explaining the definition of directional bias according to an embodiment of the present invention.

In FIG. 6, the obstacle BLK is assumed to be a rectangular Boolean model having a length of dl and a width of dw (where dl> dw), and the base station or cell coverage control device is configured to determine the location of the base station and surrounding obstacles ( It is assumed that information on the location and size of BLK) has been previously acquired and stored as geographic information. In particular, it is assumed that the base station or the cell coverage control apparatus recognizes the positions of the two vertices ((a1, b1), (a2, b2) in FIG. 2) of the obstacle closest to each base station.

As described above, the millimeter wave is mostly blocked when an obstacle such as a building is present, but the beams emitted from the directional base station (D-BS) are not partially blocked at both ends of the obstacle BLK and interfere with cell coverage of other base stations. can do. This is not suitable for the purpose of the present invention to avoid inter-beam interference using an obstacle (BLK).

In addition, since the number of user terminals (UE) located in the user concentration area An around the obstacle cannot be determined, it is difficult to determine how many of the base stations are set as directional base stations (D-BS). In some cases, if too many base stations are set as directional base stations (D-BS), inter-beam interference interfering with adjacent user terminals may be increased.

Accordingly, the present invention provides a directional bias (β). The directional bias β is a value that adjusts the angle of cell coverage in the obstacle BLK direction of the directional base station D-BS, as shown in FIG. 6, the directional base station among the total length dl of the obstacle BLK Specifies the range (βdl) to which the beam emitted from (D-BS) is irradiated. Therefore, the directional bias β may be set to a real number having a value of 0 ≤ β ≤ 1 (β ∈ [0; 1]).

When the directional bias β is 0, since the directional base station D-BS does not set the cell coverage in the direction of the obstacle BLK, all base stations BS are set as omni-directional base stations (O-BS). On the other hand, if the directional bias β is 1, all the base stations BS within a predetermined range around the obstacle BLK are set as the directional base stations D-BS.

At this time, even if the directional bias β is 1, the base station within a predetermined range around the obstacle BLK, rather than all the base stations BS, is set as a directional base station (D-BS). It is because it has (θ).

)를 조절하여 빔의 폭을 조절할 수 있다. 그러나 기지국은 기지정된 최소 조향각(θ)보다 좁게 빔의 폭을 조절 할 수 없다. 이는 최소 조향각(θ)이 각 기지국의 안테나 종류와 크기 등과 같이 기지국의 구성에 연관되기 때문이다.The base station steers the beam at the time of beamforming (

) To adjust the width of the beam. However, the base station cannot adjust the width of the beam narrower than the predetermined minimum steering angle θ. This is because the minimum steering angle θ is related to the configuration of the base station such as the antenna type and size of each base station.

7 shows an example of a directional base station selection area corresponding to a directional bias.

)으로 빔을 포밍하게 되는 반면, 제2 기지국(BS2)은 좁은 조향각(

)으로 빔을 포밍해야 한다. 그리고 제2 기지국(BS2)의 지향성 바이어스(β)에 대응하는 조향각(

)이 최소 조향각(θ)이 보다 작으므로, 제2 기지국(BS2)은 조향각(

)으로 빔을 포밍할 수 없다. 따라서 제2 기지국(BS2)이 장애물(BS) 방향으로 빔을 방사하는 경우, 빔은 장애물(BLK)의 반대편까지 도달하게 되어 다른 기지국에서 방사된 빔에 대해 간섭을 유발하게 된다.6, the directional base station selection area of FIG. 7 will be described. 6, the first base station BS1 is located adjacent to the obstacle BLK, while the second base station BS2 is located spaced apart from the obstacle BLK. Therefore, even if the directional bias β is set such that the first base station BS1 and the second base station BS2 form cell coverage for the same length Bdl in the obstacle BLK, it is located adjacent to the obstacle BLK. The first base station BS1 has a relatively wide steering angle (

), while the second base station BS2 has a narrow steering angle (

) To form the beam. And the steering angle corresponding to the directional bias (β) of the second base station (BS2) (

), the minimum steering angle θ is smaller, so the second base station BS2 has a steering angle (

) To form the beam. Therefore, when the second base station BS2 emits a beam in the direction of the obstacle BS, the beam reaches the opposite side of the obstacle BLK, causing interference to the beam emitted from another base station.

)은 서로 상이하게 획득될 것이다.The problem of the minimum steering angle θ of the beam forming is related not only to the distance from the obstacle BLK, but also to the placement position and the placement angle of the obstacle. For example, when the base station is located at the center front and at the side at the same distance as the obstacle BLK, the steering angle corresponding to the directional bias β at each base station (

) Will be obtained differently from each other.

Therefore, the directional base station (D-BS) should be selected by the position and the minimum steering angle θ of each base station, the position and size of the obstacle BLK, and the obstacle placement angle.

)은 수학식 1로 계산될 수 있다.When the positions of both edges of the obstacle BLK are ((a1, b1), (a2, b2)) as shown in FIG. 6, and the position of the base station is (x, y), the directional bias (β) Corresponding steering angle (

) May be calculated by Equation 1.

7 shows a directional base station selection region (region of D-BS) corresponding to a directional bias (β) using an average LOS ball model (Line Of Sight ball model), in which the base stations in the directional base station selection region are directional It can be selected as a base station (D-BS), and other base stations are omni-directional base stations (O-DB).

로 계산될 수 있다. 그리고 지향성 기지국(D-BS)이 사용자 단말(UE)로 메인 로브 신호(main lobe signal)를 전송할 수 있는 메인 로브 신호 거리(Rβ)는

로 계산된다. 여기서, RL은 평균 LOS 거리를 나타낸다. 따라서 메인 로브 신호 거리(Rβ)는 평균 LOS 거리(RL)보다 작다(Rβ < RL).Here, the farthest directional base station (D-BS) uses a trigonometric function

Can be calculated as And the main lobe signal distance (Rβ) that the directional base station (D-BS) can transmit the main lobe signal to the user terminal (UE) is

Is calculated as Here, RL represents the average LOS distance. Therefore, the main lobe signal distance Rβ is smaller than the average LOS distance RL (Rβ <RL).

On the other hand, in the present invention, by optimizing the directional bias (β) to a value for maximizing the average transmission rate (average rate) within the range of 0 ≤ β ≤ 1, the directional base station (D) to maximize communication performance while reducing interference -BS).

In order to optimize the directional bias (β), the obstacle recognition-based cell coverage setting method according to an embodiment of the present invention first includes a signal to interference ratio SIR for each of the user-focused area (An) and the user-unfocused area (Ar). ) Calculate coverage (Sn(β), Sr(β)). SIR coverage is a value for the probability of communication success, and the formula for calculating SIR coverage is a well-known technique and will not be described in detail here.

Then, the SIR coverage of the user terminal UE is calculated by using Equation 2 using the SIR coverages Sn(β) and Sr(β) for each of the calculated user-focused area An and the user-non-concentrated area Ar. do.

Here, γc is a user concentration rate, and refers to a ratio of time at which the user terminal UE is located close to the obstacle BLK. The user concentration ratio γc is a value used to reflect the concentration phenomenon of the user terminal UE around the obstacle BLK, and the user terminal UE is located in the user concentration area An around the obstacle BLK The average time ratio may be calculated as a probability that the user terminal UE is located in the user concentration area An at any time. The user concentration ratio (γc) is a value that can be obtained by a known technique, and detailed description is omitted here. The user concentration ratio γc has a value between 0 ≤ γc ≤ 1, and when the user concentration ratio γc is 0 (γc = 0), the user terminal UE is always far from the obstacle BLK, and the user If the concentration rate (γc) is 1 (γc = 1), the user terminal (UE) is always located around the obstacle.

)를 수학식 3에 따라 계산하여 획득한다.And if the SIR coverage of the user terminal (UE) is greater than or equal to the threshold according to Equation 2, that is, if the probability of communication success of the user terminal (UE) is greater than or equal to the threshold, the optimal directivity bias for maximizing the average transmission rate (

) Is obtained by calculating according to equation (3).

Here, Nn and Nr represent the number of user terminals UE in the user-focused area An and the user-non-concentrated area Ar, respectively, and may be obtained in advance using a statistical method.

)가 획득되면, 선택된 모든 지향성 기지국(D-BS)이 최적 지향성 바이어스(

)에 대응하는 셀 커버리지에 따라 장애물(BLK) 방향으로 빔을 포밍하도록 한다. 이때, 지향성 기지국(D-BS) 중 적어도 하나의 최소 조향각(θ)가 최적 지향성 바이어스(

)에 대응하는 조향각보다 크다면, 해당 지향성 기지국(D-BS)은 전방향성 기지국(D-BS)로 전환되어야 하며, 최적 지향성 바이어스(

)를 다시 계산하여 획득한다.Optimal directivity bias according to equation (3)

) Is obtained, all selected directional base stations (D-BS) have the optimal directional bias (

) To form the beam in the direction of the obstacle BLK according to the cell coverage corresponding to. At this time, the minimum steering angle θ of at least one of the directional base stations (D-BS) is the optimal directional bias (

), the corresponding directional base station (D-BS) should be converted to an omni-directional base station (D-BS), and the optimal directional bias (

) Is calculated again.

Hereinafter, a method for setting cell coverage based on obstacle recognition according to an embodiment of the present invention will be described in detail.

8 shows a method for setting a cell coverage based on obstacle recognition according to an embodiment of the present invention.

의 거리 이내에 배치된 모든 기지국이 포함될 수 있으며, 지향성 바이어스(β)는 최대값인 1로 설정될 수 있다.Referring to FIG. 8, a method of selecting a directional base station first selects all base stations included in a predetermined directional base station selection area around an obstacle BLK as a candidate directional base station (S110). At this time, the directional base station selection area, as described in Figure 7, from the center position of the obstacle (BLK)

All base stations deployed within a distance of may be included, and the directional bias β may be set to a maximum value of 1.

In addition, information regarding the location of the base station and the obstacle and the size of the obstacle may be stored in the cell coverage setting device or each base station through geographic information as a backhaul.

)을 수학식 1에 따라 계산할 수 있다.Since the directional bias β is initialized to the maximum value of 1, all candidate directional base stations set cell coverage to correspond to the total obstacle length dl and the steering angle corresponding to the directional bias β.

) Can be calculated according to Equation 1.

Thereafter, the SIR coverage indicating the probability of communication success of the user terminal UE is calculated according to Equation 2 (S120). That is, under the condition that all candidate directional base stations set cell coverage in the direction of the obstacle BLK, the probability of communication success of the user terminal UE at any position is calculated. Here, the arbitrary position means the position of the user terminal (UE) in the area including the user concentration area (An) and the user non-concentration area (Ar).

Then, it is determined whether the calculated SIR coverage is greater than or equal to a preset threshold (S130).

If the SIR coverage is less than the threshold, the directional bias β value is changed (S140). At this time, the directional bias β value may be changed to decrease to a predetermined unit (eg, 0.1). Then, the candidate directional base station is selected again according to the changed directional bias β (S110).

)를 계산한다(S150). 최적 지향성 바이어스(

)가 계산되면, 각각의 후보 지향성 기지국은 계산된 최적 지향성 바이어스(

)에 대응하는 셀 커버리지를 설정하고, 이에 따른 조향각을 계산한다(S160). 그리고 계산된 조향각이 기설정된 최소 조향각(θ) 이상인지 판별한다(S170).However, if the SIR coverage is greater than or equal to the threshold, the optimal directivity bias according to Equation (3)

) Is calculated (S150 ). Optimal directional bias (

) Is calculated, each candidate directional base station calculates the optimal directional bias (

Cell coverage corresponding to) is set, and a steering angle is calculated accordingly (S160). Then, it is determined whether the calculated steering angle is greater than a predetermined minimum steering angle θ (S170).

)에 대응하는 셀 커버리지를 설정한다(S180).If the steering angle calculated by all candidate directional base stations is equal to or greater than the minimum steering angle (θ), all candidate directional base stations are determined as directional base stations, and the optimal directional bias (

Cell coverage corresponding to) is set (S180).

)를 만족하는 빔을 포밍할 수 없다. 즉 셀 커버리지를 설정할 수 없다. 따라서 후보 지향성 기지국에서 제외된다(S190). 그리고 나머지 후보 지향성 기지국을 기반으로 SIR 커버리지부터 다시 계산한다(S120).On the other hand, if the calculated steering angle is less than the minimum steering angle (θ), the corresponding base station is the optimal directional bias (

) Cannot be formed. That is, cell coverage cannot be set. Therefore, it is excluded from the candidate directional base station (S190). Then, SIR coverage is calculated again based on the remaining candidate directional base stations (S120).

As described above, the method of selecting the directional base station shown in FIG. 8 to set the cell coverage is performed through a separate cell coverage setting apparatus connected to a plurality of base stations through a backhaul, or each of the plurality of base stations is a candidate directional base station. It can be performed through a mutual exchange of information through a backhaul. In addition, the cell coverage setting device may be a communication system control server or a macro base station, but is not limited thereto.

)를 만족할 수 있는 지향성 기지국을 선택하고, 선택된 지향성 기지국이 장애물 방향으로 셀 커버리지를 설정할 수 있도록 함으로써, 빔간 간섭을 제거할 수 있을 뿐만 아니라, 평균 전송 속도를 높일 수 있어 통신 성능을 향상 시킬 수 있다.Therefore, the obstacle recognition-based cell coverage setting method illustrated in FIG. 8 includes SIR coverage and optimal directivity bias among candidate directional base stations within a predetermined range (

By selecting a directional base station that satisfies) and allowing the selected directional base station to set cell coverage in the direction of an obstacle, it is possible to remove inter-beam interference and increase the average transmission speed, thereby improving communication performance. .

9 illustrates a method in which a directional base station and an omni-directional base station set according to an obstacle recognition-based cell coverage setting method according to an embodiment of the present invention communicate with a user terminal.

)에 대응하여 설정된 셀 커버리지 내에서 기준 신호를 송신한다.When the directional base stations are selected by FIG. 8, and the cell coverage of each directional base station is set, as shown in FIG. 9, the selected directional base stations (D-BS) respectively transmit a reference signal (S210). At this time, each of the directional base stations (D-BS) is an optimal directional bias (BLK) direction (

), the reference signal is transmitted within the set cell coverage.

At least one user terminal UE located in the user concentration area An around the obstacle BLK determines whether a reference signal is received (S220 ). If a reference signal is received, a pilot signal is transmitted by selecting a directional base station (D-BS) that transmits a reference signal of maximum power among the received reference signals (S230). Accordingly, the directional base station (D-BS) receiving the pilot signal performs communication with the user terminal (UE) (S240).

On the other hand, if it is determined that the reference signal has not been received, the user terminal UE transmits an inverse pilot signal (S250). At this time, the user terminal (UE) may broadcast an inverse pilot signal in all directions. This is to prevent a network coverage hole from being generated by an obstacle BLK or a cell coverage of the directional base station (D-BS) is limited.

Then, the omni-directional base station (O-BS) receiving the inverse pilot signal transmits an acknowledgment signal corresponding to the inverse pilot signal, and the user terminal (UE) determines whether the acknowledgment signal is received from the omni-directional base station (O-BS). (S260).

If an acknowledgment is received, the user terminal UE selects an omni-directional base station (O-BS) that transmits the acknowledgment received at the maximum power among the received responses and transmits a pilot signal (S270). Then, the omni-directional base station (O-BS) receiving the pilot signal performs communication with the user terminal (UE) (S280).

However, if an acknowledgment signal is not received, the user terminal UE again determines whether a reference signal is received from the directional base station (D-BS) (S220).

Therefore, as shown in FIG. 9, a directional base station (D-BS) or an omni-directional base station (O-BS) can perform communication with a user terminal and prevent network coverage holes from being generated.

The method according to the present invention can be implemented as a computer program stored in a medium for execution on a computer. The computer readable medium herein can be any available medium that can be accessed by a computer, and can also include any computer storage medium. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, and ROM (readable) Dedicated memory), RAM (random access memory), CD (compact disk)-ROM, DVD (digital video disk)-ROM, magnetic tape, floppy disk, optical data storage, and the like.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely exemplary, and those skilled in the art will understand that various modifications and other equivalent embodiments are possible therefrom.

Therefore, the true technical protection scope of the present invention should be defined by the technical spirit of the appended claims.

UE: User terminal
D-BS: directional base station
O-BS: Omni-directional base station
BLK: Obstacle

Claims (11)

In a mobile communication system comprising a plurality of base stations,
Determining a candidate directional base station included within a predetermined range from the obstacle among the plurality of base stations by using the pre-stored base station location and the location and size information of the obstacle; And
At least one of the candidate directional base stations sets cell coverage in the obstacle direction, and selects a directional base station performing communication with a user terminal in the set cell coverage; Including,
The step of determining the candidate directional base station
Setting a directional bias for designating a range to which a beam emitted from the directional base station of the entire length of the obstacle is to be irradiated; And
Selecting at least one base station within a range corresponding to the directional bias from the obstacle among the plurality of base stations as a candidate directional base station; Obstacle recognition-based cell coverage setting method of a mobile communication system comprising a. delete The method of claim 1, wherein the directional bias
A method of setting cell coverage based on obstacle recognition in a mobile communication system, wherein the initial value is a real number having a value of 0 ≤ β ≤ 1. The method of claim 3, wherein selecting the candidate directional base station
From the obstacle in response to the directional bias

(Where θ is a minimum steering angle, β is a directional bias, and dl is a length of an obstacle.) A method of setting cell coverage based on obstacle recognition in a mobile communication system, characterized in that a base station within a distance is selected as the candidate directional base station. The method of claim 4, wherein the step of selecting as the directional base station
Calculating SIR coverage indicating a probability of communication success of the user terminal when all of the at least one candidate directional base station operates as the directional base station;
Calculating the optimal directional bias to maximize the transmission speed of the user terminal when the SIR coverage is equal to or greater than a preset threshold;
Each of the candidate directional base stations calculating a steering angle corresponding to the optimal directional bias; And
If the calculated steering angle is equal to or greater than a predetermined minimum steering angle of each candidate directional base station, selecting the candidate directional base station as a directional base station and setting cell coverage according to the calculated steering angle; Obstacle recognition-based cell coverage setting method of a mobile communication system comprising a. The method of claim 5, wherein the step of selecting as the directional base station
If the SIR coverage is below a threshold, changing the directional bias to select a candidate directional base station again; And
If the calculated steering angle is less than a minimum steering angle of at least one candidate directional base station, excluding a candidate directional base station having a minimum steering angle from the candidate directional base station; Obstacle recognition-based cell coverage setting method of a mobile communication system further comprising a. According to claim 5, The steering angle (

)silver
Equation

(Where θ is the minimum steering angle, β is the directional bias, (x, y) is the location of the base station, ((a1, b1), (a2, b2)) represents the position of both edges of the obstacle.)
Is calculated according to,
The SIR coverage (S)
Equation

(Wherein, Sn (β), Sr (β) represents the SIR coverage in each of the user concentration area (An) within the predetermined distance around the obstacle and the other non-concentration area (Ar), γc is the user terminal (UE ) Is the percentage of time that is located in the user concentration area (An).
Obstacle recognition based cell coverage setting method of a mobile communication system, characterized in that calculated by. The method of claim 7, wherein the optimal directional bias (

)
Equation

(Nn and Nr represent the number of user terminals (UE) in the user-focused area (An) and the user non-focused area (Ar), respectively.)
Obstacle recognition based cell coverage setting method of a mobile communication system, characterized in that calculated by. The method of claim 1, wherein the method for setting cell coverage based on obstacle recognition in the mobile communication system is
A method for setting cell coverage based on obstacle recognition in a mobile communication system, characterized in that a base station not selected as the directional base station among the plurality of base stations is set as an omni-directional base station capable of performing beamforming in all directions regardless of an obstacle. The method of claim 9, wherein the method for setting the cell coverage based on obstacle recognition in the mobile communication system is
The at least one directional base station transmitting a reference signal;
A directional base station receiving a pilot signal corresponding to the reference signal from the user terminal communicating with the user terminal;
Receiving an inverse pilot signal transmitted from a user terminal that does not receive the reference signal by an omni-directional base station excluding the at least one directional base station among the plurality of base stations;
Transmitting an acknowledgment signal to the user terminal by the omni-directional base station receiving the inverse pilot signal; And
An omni-directional base station receiving a pilot signal corresponding to the response signal from the user terminal communicating with the user terminal; Obstacle recognition-based cell coverage setting method of a mobile communication system further comprising a. It is selected according to the location and size information of a base station and an obstacle stored in advance among a plurality of base stations, is disposed within a predetermined range from an obstacle, sets cell coverage in the direction of the obstacle, and performs communication with a user terminal in the set cell coverage At least one directional base station; And
At least one omni-directional base station performing communication with a user terminal outside of cell coverage set by the directional base station, as a base station excluding the directional base station among the plurality of base stations; Including,
The directional base station
According to the base station position and the position and size information of the obstacle, the obstacle recognition-based cell coverage setting is arranged within a range corresponding to a directional bias set to designate a range in which the beam emitted from the base station is radiated out of the entire length of the obstacle system.

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