KR101237384B1 - Apparatus and method for bemaforming in a wireless communication network - Google Patents

Abstract

The present invention obtains a first weight vector of a main beam formed for data transmission for beam-forming in a wireless communication network, and generates a second weight vector having orthogonality to the obtained first weight vector. After that, the generated second weight vector is applied to an arbitrary signal, and the signal to which the second weight vector is applied is transmitted together with the data to form a complementary beam.

Wireless communication network, beamforming, main beam, complementary beam, weight vector processing unit, power allocation unit

Description

Apparatus and method for forming a beam in a wireless communication network {APPARATUS AND METHOD FOR BEMAFORMING IN A WIRELESS COMMUNICATION NETWORK}

1 is a diagram schematically illustrating a structure of a wireless communication network to which a general beamforming technique is applied;

2 is a diagram schematically illustrating a structure of a wireless communication network to which a beamforming technique is applied according to an embodiment of the present invention;

3 is a view schematically showing the structure of a beam forming apparatus according to an embodiment of the present invention;

4 is a flow chart schematically showing a beam forming method according to an embodiment of the present invention;

5 is a graph schematically showing a beam pattern according to an embodiment of the present invention.

TECHNICAL FIELD The present invention relates to a wireless communication network, and more particularly, to an apparatus and method for beamforming in a wireless communication network.

A general communication network, for example, a local area network (LAN), is a collection of personal terminals, mainframes, and workstations connected to a communication line of 300 meters (m) or less. It is a high-speed communication network that connects the distance between terminals to the point where current or radio signals can be transmitted accurately, that is, to enable employees to most effectively use equipment installed in an institution's building. As a communication line applied to such a LAN, a wired network that directly transfers electrical signals was mainly used. Since then, due to the development of wireless protocols, the situation is gradually replaced by a wireless communication network using a wireless network that uses radio waves to transmit signals. In one such wireless communication network, a LAN using a wireless network is commonly referred to as a wireless local area network (WLAN), which is based on IEEE 802.11 proposed by the Institute of Electrical and Electronics Engineers (IEEE). The wireless LAN based on IEEE 802.11 has grown enormously over the last few years, and is expected to develop rapidly in the future thanks to the advantage of convenient network connection.

1 is a diagram schematically illustrating general wireless communication networks.

Referring to FIG. 1, a wireless communication network is a fixed node, that is, an access point (AP) 110 and a mobile node that receives a service from the access point 110, that is, terminals 111, 113, 115).

In this case, the access point 110 performs a function similar to that of a hub of an existing wired LAN. In addition, the access point 110 has a service area for communicating with a plurality of terminals including the terminals 111, 113, and 115.

Here, it is assumed that the access point 110 communicates with each of the terminals 111, 113, and 115 using an array antenna. The access point 110 generates a beam 120 by allocating power toward the terminal 111 to communicate with the terminal 111 to transmit data. In this case, the beam 120 generated by the access point 110 to communicate with the first terminal 111 is called a main beam, and the access point 110 is connected to the main beam through the main beam. Data is transmitted to the first terminal 111.

In addition, when the access point 110 communicates with the terminals 111, 113, and 115, a carrier measurement multiple access (CSMA: Carrier Sense Multiple Access (CSMA) hereinafter referred to as 'CSMA') communication is performed. Assume Therefore, each terminal attempts communication after confirming whether another terminal is communicating with the access point 110 through the shared channel for channel access with the access point 110. For example, when the second terminal 113 wants to communicate with the access point 110, energy of a carrier is used to check whether other terminals 111 and 115 are communicating. Measure Thus, when it is determined that the access point 110 is not currently communicating with the terminal, the second terminal 113 attempts to transmit data to the access point 110. However, when the access point 110 communicates with the first terminal 111, for example, the access point 111 reconfirms whether or not the access point 111 communicates after a predetermined time elapses.

However, the second terminal 113 may exist in a shaded area where it is not possible to determine whether the access point 110 is currently communicating with the first terminal 111. If the second terminal 113 exists in the shaded area as described above and cannot detect that the access point 110 is currently communicating with the first terminal 111, the second terminal 113. Will attempt to transmit data for communication with the access point 110.

Similarly, in addition to the second terminal 113, terminals existing in the shadow area where the access point 110 can not detect communication will also attempt to transmit the same data as the second terminal.

That is, as described above, terminals existing in the shaded area in the wireless communication network will attempt to connect to the access point 110 currently in communication. In this case, the terminals in the shaded area consume unnecessary power. In addition, as the terminals of the shadow area attempt to transmit to the access point 110, a collision occurs in the access point 110. As a result, the collision occurring in the access point causes the data throughput of the access point 110 to decrease.

As a result, in the wireless communication network using the CSMA scheme, there is a shaded area where communication of the access point cannot be confirmed. Due to the shaded area, unnecessary power consumption of the terminal and a reduction in data throughput of the access point, as described above, may occur. There was a problem that the overall system performance is reduced.

Accordingly, an object of the present invention is to propose a beam forming apparatus and method for guaranteeing overall system performance in a wireless communication network.

Another object of the present invention is to propose a beam forming apparatus and method for removing a shadow area in a wireless communication network.

It is another object of the present invention to propose a beam forming apparatus and method for reducing unnecessary power consumption of a terminal for communication with an access point in a wireless communication network.

Another object of the present invention is to propose a beam forming apparatus and method for preventing a collision due to terminals attempting to transmit from an access point in a wireless communication network.

In accordance with another aspect of the present invention, there is provided a beam forming method using an access point having an array antenna in a carrier measurement multiple access environment, including: forming a main beam using the array antenna; And forming a complementary beam to have a uniform radiation shape in the shaded area while being orthogonal to the main beam at a power sufficient to receive a signal by a terminal in the shaded area formed by the main beam.

An apparatus of the present invention for achieving the above object is a beam-forming apparatus provided in an access point in a wireless communication network based on a carrier measurement multiple access environment, the first weight vector for the main beam, A weight vector processor for generating a second weight vector for the complementary beam, and a power to which the signal is received by the terminal in the shadow area formed by the main beam and allocating power for the main beam; The main beam is formed by using a power allocating unit for allocating the first weight vector and the first weight vector generated for the array antenna and the main beam and the power allocated for the main beam and generating the array beam and the supplemental beam. Uniform radiation in the shadowed area orthogonal to the main beam using a second weight vector and the power allocated for the complementary beam So as to have a state and a transmission section which forms the complementary beam.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

In the present invention, a shadow area of a transmitter, for example, an access point (AP) is removed in a wireless communication network using a carrier measurement multiple access (CSMA: Carrier Sense Multiple Access (CSMA)) scheme. A beam forming apparatus and method are proposed.

Acquire a first weight vector of the main beam formed for the data transmission, generate a second weight vector having orthogonality to the acquired first weight vector, and then use the second weight vector to shade the shadow. An apparatus and method for forming a complementary beam for removing an area is proposed. Here, the main beam refers to a beam generated by allocating power to communicate with a receiver, that is, a mobile station (MS), using an array antenna in the transmitter, that is, the access point. In addition, the complementary beam is a beam generated in order to remove the shadow area in which the power of the main beam cannot be measured, that is, it is not possible to determine whether the access point is communicating with another terminal.

Meanwhile, in the wireless communication network of the present invention, it is assumed that the communication is performed using the CSMA method, and the CSMA method is carrier measurement multiple access / collision detection (CSMA / CD) and carrier measurement multiple access. All methods such as Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA), etc. are collectively referred to.

2 is a diagram schematically illustrating a structure of a wireless communication network according to an embodiment of the present invention.

Referring to FIG. 2, the wireless communication network includes a fixed node, that is, an access point 210, and a mobile node that receives a service from the access point 210, that is, terminals 211, 213, and 215. .

In this case, the access point 210 performs a function similar to that of a hub of an existing wired LAN. The access point 210 also has a service area for communicating with a plurality of terminals, including the terminals 211, 213, 215.

In the present invention, it is assumed that the access point 210 communicates with each of the terminals 211, 213, and 215 using at least one array antenna that forms a beam. The access point 210 generates a beam 230 by allocating power toward the terminal 211 to communicate with the terminal 211 to transmit data. In this case, the beam 230 generated by the access point 210 to communicate with the first terminal 211 is called a main beam, and the access point 210 is connected to the main beam through the main beam. Data is transmitted to the first terminal 211.

Each of the second terminal 213 or the third terminal 215 except the first terminal 211 confirms whether the access point 210 currently communicates with another terminal other than itself in order to communicate with the access point. do. That is, the second terminal 213 or the third terminal 215 measures the power of the carrier wave.

At this time, in the present invention, the supplementary beam 250 shown in the drawing of the access point 210 is proposed to remove the shadow area of the access point 210. Accordingly, the terminals existing in the cell of the access point 210 detect that the access point 210 communicates with another terminal through the complementary beam 250 and perform data transmission or access attempt to the access point. I never do that. Thus, a collision of 210 at the access point does not occur.

In the present invention, a portion of the transmission power used in the main beam is allocated to the supplemental beam. The main beam 230 of the access point allocates a portion of the transmission power of the existing main beam 240 that does not form a security beam, so that the main beam 230 of the present invention has a smaller size than the existing main beam 240.

In FIG. 2, for convenience of description, an example of an access point generating one main beam is described as a reference. However, even when one or more main beams are used, it is possible to generate a complementary beam perpendicular to each main beam.

Next, a structure of the access point 210 for generating the complementary beam 250 will be described in detail with reference to FIG. 2.

3 is a view schematically showing the structure of a beam forming apparatus according to an embodiment of the present invention. 3 illustrates the structure of the access point 210 that generates the supplemental beam 250 in detail.

Referring to FIG. 3, the access point forming the complementary beam includes a weight vector processor 311, multipliers 313 and 315, a power allocator 317, a mixer 319, and a transmitter 321.

The weight vector processor 311 calculates a weight vector of the main beam for the access point to communicate with the terminal, and calculates a second weight vector that maintains orthogonality with the weight vector of the main beam using the calculated weight vector of the main beam. Create

In general, the weight vector of the main beam is a complex pair of array response vectors, which is represented by Equation 1 below.

는 공액 복소수 전치(conjugate and transpose) 연산을 의미한다. 또한 상기 a는 배열응답벡터이다. 그러면 여기서 상기 배열응답벡터에 대해 간단히 설명하기로 한다. In Equation 1

Means conjugate conjugate and transpose operation. A is an array response vector. The array response vector will now be briefly described.

It is assumed that there is a specific terminal k in which the access point communicates with the access point via a predetermined number, N transmit antennas, connected to the transmitter for communication with the terminal. Here, the received signal of the terminal k is expressed by Equation 2.

은 k번째 단말기가 수신한 신호의 m 시간의 샘플 신호이고, 상기

는 N x 1의 크기를 가지며 l번째 다중경로에 의해 지연되는 단말기 k에 대한 채널값이고, 상기

는 상기 k에 대한 액세스 포인트에서의 송신 신호이고, 상기 n은 독립적인 백색잡음(white noise)이다. 여기서 상기

는 각

의 도래각(DOA: Direction of Arrival)을 가지며, 하기의 수학식 3과 같이 나타낼 수 있다. remind

Is a sample signal of m time of the signal received by the k-th terminal,

Is the channel value for terminal k having the size of N × 1 and delayed by the l-th multipath,

Is the transmission signal at the access point for k, and n is the independent white noise. Where above

Is each

It has a direction of arrival (DOA) and can be expressed as Equation 3 below.

Where g is the channel gain, and a is defined as Equation 4 below as an array response vector.

The array response vector is shown in Equation 4 as an example. The array response vector is a vector in which a phase shift due to propagation delay of radio waves is arranged for each element of each linear array antenna when a terminal transmits a signal to an access point using a linear array antenna.

Next, the access point shows a signal received by the terminal by applying a weight vector for generating the main beam in Equation 5 below.

The y (m) is a signal received by the terminal at an arbitrary time, that is, m time, by the access point applying a weight vector. And s (m) is a signal transmitted by the access point in the m time, and n (m) is noise for the signal transmitted in the m time. Where h is a channel vector and w is a weight vector for main beam formation.

Equation 1 and Equation 3 may be substituted into Equation 5 to represent Equation 6 below.

Here, Equation 6 represents received signals at the terminal when the access point transmits a signal formed by the main beam. Therefore, as shown in Equation 6, a signal received by the terminal by forming a main beam obtains a gain g.

In the present invention, the overall beamforming weight vector including the weight vectors of the main beam and the supplementary beam is shown in Equation 7 below.

는 주빔 형성을 위한 가중치 행렬이며,

는 보완빔 형성을 위한 가중치 행렬이다. remind

Is a weight matrix for main beam formation,

Is a weighting matrix for forming the complementary beam.

을 사용하여 상기 주빔과 직교하는 가중치 벡터를 생성한다. 이때 생성된 가중치 벡터가 본 발명의 보완빔에 적용되는 가중치 벡터이다. The weight vector processor 311 may include a weight vector of the main beam,

To generate a weight vector orthogonal to the main beam. The generated weight vector is a weight vector applied to the complementary beam of the present invention.

The weight vector processor 311 may obtain a weight vector of the main beam using an array response vector as shown in Equation (1). In this case, a method of calculating the weight vector of the main beam may use, for example, a minimum variance distortion response (MVDR) technique or a conventional beamforming (CB) technique. In addition to the above-described techniques, the weight vector of may be obtained using other techniques for obtaining the weight vector of the main beam.

Meanwhile, the weight vector processing unit 311 uses a Gram-Schmidt orthogonalization technique in order to obtain the weight vector of the complementary beam.

The access point of the present invention is capable of generating at least one main beam, and generates a weight vector according to each main beam. Therefore, assuming that the number of the main beams is K, K weight vectors of the main beams are generated.

Therefore, the number of weight vectors of the complementary beam is shown in Equation 8 below.

L = N-K

L is the number of weight vectors of the complementary beams, N is the number of linear array antennas, and K is the number of weight vectors of the main beams. Here, K may be the number of main beams, since each weight beam vector is obtained for each main beam. Accordingly, the weight vector processor 311 may obtain a weight vector of the main beam corresponding to the at least one main beam and generate a weight vector of the complementary beam orthogonal to the weight vector.

First, N-K linear independent vectors for using the Gram Schmidt orthogonalization method are shown in Equation 9 below.

는 임의의 상수이다. 상기 가중치 벡터 처리부(311)는 상기 그람-슈미츠 직교화 기법을 적용하기 위해서 각 주빔에 상응하는 주빔의 가중치 벡터들 중 첫 번째 주빔에 상응하는 가중치 벡터를 기준 벡터로 설정하면,

이 된다. 다시 말해, 상기 가중치 벡터 처리부(311)는 상기 기준 벡터를 주빔의 가중치 벡터 즉, K개의 주빔 형성을 위한 K개의 가중치 벡터중 첫 번째 가중치 벡터로 설정한다. 상기 기준 벡터에 직교하는 직교 벡터를 획득하는 수학식은 하기의 수학식 10에 나타내었다.Where above

Is any constant. When the weight vector processing unit 311 sets the weight vector corresponding to the first main beam among the weight vectors of the main beams corresponding to each main beam in order to apply the Gram-Schmids orthogonalization technique,

. In other words, the weight vector processor 311 sets the reference vector as the weight vector of the main beam, that is, the first weight vector among the K weight vectors for forming the K main beams. Equation for obtaining an orthogonal vector orthogonal to the reference vector is shown in Equation 10 below.

는 상기 수학식 10에서 생성한 N x 1 크기의 선형독립 벡터이고,

는 순차적으로 생성되는 N x 1 크기의 직교 벡터이다.remind

Is a linear independent vector of size N × 1 generated by Equation 10,

Is an orthogonal vector of size N × 1 that is generated sequentially.

Orthogonal vectors may be obtained sequentially using Equation 10, and the obtained orthogonal vectors are normalized to obtain N-K orthogonal weight vectors for forming N-K orthogonal beams. The orthogonal vector after performing the normalization is shown in Equation 10 below.

The beamforming matrix including the orthogonal vectors obtained using Equation 11 obtained through the normalization is shown in Equation 12 below.

Equation 12 is obtained by extending the acquired orthogonal vectors into a square matrix of N × N. A beam may be formed using the beamforming matrix of Equation 11 to form a complementary beam to have an omnidirection radiation pattern.

As described above, the weight vector processor 311 obtains a weight vector for forming N-K complementary beams using the weight vectors of the N main beams.

를 입력받고, 상기 가중치 벡터 처리부(311)에서 출력된 주빔 형성을 위한 가중치 벡터,

을 입력받는다. 다음으로, 상기 제 1 곱셈기(313)는 상기 송신 신호에 가중치 벡터를 곱하여 상기 전력 할당부(317)로 출력한다.On the other hand, the first multiplier 313 is a signal to be transmitted to the terminals in the access point,

Receives a weight vector for forming the main beam output from the weight vector processor 311,

Get input. Next, the first multiplier 313 multiplies the transmission signal by a weight vector and outputs the weighted vector to the power allocator 317.

를 입력받고, 상기 가중치 벡터 처리부(311)에서 출력된 보완빔 형성을 위한 가중치 벡터

를 입력받는다. 여기서 상기

는 상기 보완빔 형성을 위해서 임의로 송신하는 신호로서 미리 설정된 임의의 신호이다. 다음으로, 상기 제 2 곱셈기(315)는 상기 임의의 송신 신호에 보완빔 형성을 위한 가중치 벡터를 곱하여 상기 전력 할당부(317)로 출력한다.The second multiplier 315 is a random signal for forming the complementary beam

Is received, the weight vector for forming the complementary beam output from the weight vector processor 311

. Where above

Is an arbitrary signal that is arbitrarily transmitted for forming the complementary beam. Next, the second multiplier 315 multiplies the arbitrary transmission signal by a weight vector for forming a complementary beam, and outputs the weighted vector to the power allocator 317.

The power allocator 317 receives the output signals of the first multiplier 313 and the second multiplier 315, and outputs the output signals of the first multiplier 313 and the second multiplier 315. Allocate power. In order to form the complementary beam, the supplementary beam requires a power level higher than that of the noise signal, and the power allocator 317 allocates power to the supplementary beam to power level higher than that of the noise signal. To have. The power allocating unit 317 generates a supplementary beam by allocating a part of the power allocated to the existing main beam to the supplementary beam without additional power for generating the supplementary beam.

In general, the power level of the complementary beam should have a lower beam forming power level than a general transmission signal, and in order for the main beam to obtain the maximum gain, the supplemental beam should be formed with the minimum power capable of measuring carrier energy. For this purpose, power control of each beamforming vector is required. The power allocator 317 allocates the total transmission power to each beam, which is represented by Equation 13 below.

은 주빔과 보완빔에 나누어 할당하며, 보완빔의 전력 준위

와 주빔의 전력 준위

이 나타나 있다. 이에 상기 전체 빔에 할당된 전력을 1로 정규화하면, 상기 보완빔에 할당된 전력을

이고, 주빔에 할당되는 전력은 (1-

)

이 된다.Full power

Is divided into main beam and complementary beam, and the power level of complementary beam

And power levels of the main beam

Is shown. Accordingly, when the power allocated to the entire beam is normalized to 1, the power allocated to the supplementary beam is adjusted.

And the power allocated to the main beam is (1-

)

.

The power allocator 317 controls the power levels of the main beam and the complementary beam, respectively, and outputs the power to the mixer 319.

The mixer 319 mixes the signals output from the power allocator and outputs the mixed signals to the transmitter 321.

The transmitter 317 performs a wireless process such as modulating, up-converting the radio signal into a radio signal, and then transmits it through an antenna to form a beam.

는 하기의 수학식 14에 나타내었다.Signal output by the access point

Is shown in Equation 14 below.

에 가중치 벡터들(

,

)이 적용되 어 송신되어 상기 도 2에서 나타난 바와 같은 빔 패턴을 형성한다. The output signal of the access point at any time m is a signal for forming the complementary beam with the transmission signal s (m) of the access point.

Weights vectors

,

) Is applied to form a beam pattern as shown in FIG.

Next, an operation of the access point for generating the complementary beam will be described with reference to FIG. 4.

4 is a diagram schematically illustrating a beam forming method according to an embodiment of the present invention. 4 illustrates the operation of an access point generating a supplemental beam.

Referring to FIG. 4, in step 411, the access point obtains a first weight vector and proceeds to step 413. Here, the first weight vector may be obtained using an array response vector as a weight vector for forming the main beam.

In step 413, the access point generates a second weight vector orthogonal to the first weight vector using the first weight vector, and proceeds to step 415. Here, the second weight vector is a weight vector for generating a complementary beam, and the second weight vector is a vector generated by using a Gram-Schmids orthogonalization technique. Since generating the second weight vector using the Gram-Schmids orthogonalization technique has been described with reference to FIG. 3, a detailed description thereof will be omitted.

In step 415, the access point applies the second weight vector to an arbitrary transmission signal and proceeds to step 417. The arbitrary transmission signal is any transmission signal used for generating the complementary beam. Thus, the arbitrary transmission signal is not limited to a specific signal, but a signal transmitted from the access point to form a complementary beam. Thus, the arbitrary signal includes specific information for forming the complementary beam, but the information includes information that is meaningless as a signal transmitted for forming the supplementary beam.

은 0.01 정도의 값을 가지며, 전체 빔의 송신 전력이 1이라고 하면 1% 정도의 크기를 갖는다. 다시 말해, 전체 빔의 송신 전력에서 99%는 주빔에 할당하고, 1%는 보완빔에 할당하여도 상기 액세스 포인트에서 발생하는 음영지역을 제거할 수 있다. In step 417, the access point allocates power for beamforming to the transmission signal to which the second weight vector is applied, and proceeds to step 419. In the case of allocating the power, power is allocated such that the power level of the complementary beam has a power level higher than that of the noise signal. For example, the power level of the complementary beam may determine that the channel of the access point is in use even in a shaded area when the signal to noise ratio (SNR) has a value of -20 dB. At this time, in Equation 12

Has a value of about 0.01, and if the transmission power of the entire beam is 1, it has a size of about 1%. In other words, even if 99% of the transmission power of the entire beam is allocated to the main beam and 1% is allocated to the supplemental beam, the shadow area generated at the access point can be removed.

In step 419, the access point transmits a signal to which the second weight vector is allocated to form a complementary beam. In this case, the generated complementary beam forms a complementary beam having a uniform radiation pattern, that is, an omnidirectional radiation pattern, in an area excluding the main beam by using a second weight vector orthogonal to the first weight vector.

As described above, the number of the first weight vectors may be plural, and the second weight vector is generated in consideration of the number of the first weight vectors. The access point generates a number corresponding to a difference from the number of linear array antennas used in the access point and the number of the first weight vectors.

Next, a beam pattern according to the present invention will be described with reference to FIG. 5.

5 is a graph schematically showing a beam pattern according to an embodiment of the present invention.

Referring to FIG. 5, a beam pattern is illustrated by forming a complementary beam according to the present invention. In the present invention, in order to form the complementary beam, a multi-band orthogonal frequency division multiple access protocol (MBOA: Multi-Band OFDM Alliance) environment Experiments were performed at 3.1-3628 GHz, which is the first band, and the number of points of the Orthogonal Frequency Division Multiplexing (OFDM) is a graph obtained using 128. The vertical axis of the graph represents power (dB), and the horizontal axis represents azimuth.

= 0.01)로 가정하였다. In FIG. 5A, the number of transmit antennas is four and one main beam is formed. In (b), the number of transmitting antennas is 16, and three main beams are formed. The main beam forming method uses a conventional beamforming method, and a hamming window is used to obtain a sufficient depth. And the power level of the complementary beam is -20dB, that is, 1% of the total transmit power (

= 0.01).

In (a), the solid line represents the power level of the entire beam as the sum of the power levels of the main beam and the complementary beam. The dotted line indicates the power level of the complementary beam, and the dotted line indicates the power level of the main beam. As shown in the figure, it can be seen that the power level lost in the main beam is not significantly different at 30 degrees, which is the formation area of the main beam, when compared with the main beam when no complementary beam is formed.

In addition, it can be seen that interference by the complementary beam does not occur in the region where the main beam is formed. That is, in the present invention, as described above, by forming the complementary beam, the terminals in the shaded area detect the power of the supplementary beam to confirm the use of the channel, and thus, the terminal does not attempt to transmit data, thereby reducing the power consumption of the terminal. It is possible to.

In the case (b), 16 transmission antennas are used and three main beams are formed. The main beam angles are -50 degrees, 10 degrees and 50 degrees. At this time, the power level of the complementary beam is -20dB as in (a). Therefore, it can be seen that the power loss of the main beam is hardly different from the case of not forming the complementary beam. Here, it can be seen that the complementary beam does not generate interference by the supplementary beam in the main beam region.

In the present invention, at least one main beam is formed to form a complementary beam orthogonal to the main beam at an access point communicating with at least one or more terminals to remove the shadow area of the access point, thereby allowing the terminal to communicate with the access point. It is possible to judge accurately.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention generates a complementary beam having an omnidirectional radiation pattern in an area excluding the main beam area because the present invention has orthogonality to the main beam in a wireless communication network. Therefore, the wireless communication network of the present invention has the advantage that it is possible to remove the shadow area. In addition, the terminal has an advantage of not unnecessary power consumption for data transmission to the access point, and has the advantage that it is possible to reduce the collision at the access point. Thus, by using the complementary beam in the present invention has the advantage that it is possible to improve the overall system performance of the wireless communication network.

Claims (17)

A beamforming method by an access point having an array antenna in a carrier measurement multiple access environment, Forming a main beam using the array antenna; Forming a complementary beam using the array antenna so as to have a uniform radiation shape in the shaded area while being orthogonal to the main beam at a power sufficient to detect the reception of a signal by a terminal in the shaded area formed by the main beam; Beam forming method comprising. The method of claim 1, The power to the extent that the reception of the signal is detected by the terminal is a power enough to the terminal to receive the complementary beam at a power level higher than the power level of the received noise signal. The method of claim 1, The main beam is formed using the array antenna to obtain a first weight vector and transmit data by applying the obtained first weight vector, The complementary beam is formed using the array antenna to transmit an arbitrary signal by applying a second weight vector generated to be orthogonal to the first weight vector. The method of claim 3, wherein And the second weight vector is generated using a Gram-Schmidt orthogonalization technique. 5. The method of claim 4, The second weight vector is generated using the orthogonal vectors obtained by the following equation.

Is a linear independent vector of size N x 1,

Is an orthogonal vector of size N x 1 that is generated sequentially. delete delete delete A beam-forming apparatus provided in an access point in a wireless communication network based on a carrier measurement multiple access environment, A weight vector processor for generating a first weight vector for the main beam and a second weight vector for the complement beam; A power allocator for allocating power for the main beam and allocating power for the complementary beam to the extent that the reception of a signal is detected by a terminal in a shadow area formed by the main beam; The main beam is formed using the first weight vector generated for the array antenna and the main beam and the power allocated for the main beam, and the second weight vector and the supplementary beam generated for the array antenna and the supplemental beam. And a transmitter configured to form the complementary beam to have a uniform radiation shape in the shaded area while being orthogonal to the main beam by using the power allocated for the beamforming apparatus. The method of claim 9, The power to the extent that the reception of the signal is detected by the terminal is a power to the extent that the terminal can receive the complementary beam at a power level higher than the power level of the received noise signal. The method of claim 9, wherein the transmitting unit, The main beam is formed using the array antenna to obtain a first weight vector and transmit data by applying the obtained first weight vector, The complementary beam is formed using the array antenna to transmit an arbitrary signal by applying a second weight vector generated to be orthogonal to the first weight vector. The method of claim 11, And the weight vector processing unit generates the second weight vector using a Gram-Schmidt orthogonalization technique. 13. The method of claim 12, And the weight vector processing unit generates the second weight vector using orthogonal vectors obtained by the following equation.

Is a linear independent vector of size N x 1,

Is an orthogonal vector of size N x 1 that is generated sequentially. delete delete delete delete

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