KR102164972B1 - Method and apparatus for opportunistic interference alignment in multi-user multi-input multi-output transmission - Google Patents

Abstract

Disclosed is a method and apparatus for opportunistic interference alignment in MU-MIMO transmission. The opportunistic indirect alignment method includes broadcasting a random beam, receiving feedback information determined based on the random beam from a terminal device, and at least one terminal device to transmit data from among the terminal devices based on the feedback information. Selecting, adjusting transmission power based on the feedback information; And transmitting data to the at least one selected terminal device based on the adjusted transmission power.

Description

Opportunistic interference alignment method and apparatus in MU-MIMO transmission {METHOD AND APPARATUS FOR OPPORTUNISTIC INTERFERENCE ALIGNMENT IN MULTI-USER MULTI-INPUT MULTI-OUTPUT TRANSMISSION}

The following description relates to an opportunistic interference alignment method and transmission power control technology in WLAN.

LAN (Local Area Network), a local area network, is largely divided into wired LAN and wireless LAN. Wireless LAN is a method of performing communication on a network using radio waves without using a cable. The emergence of wireless LAN has emerged as an alternative to solve the difficulties of installation, maintenance, and movement due to cabling, and the necessity is increasing due to the increase of mobile users.

The configuration of the wireless LAN consists of an access point ("AP") and a terminal device (Station, STA). The AP is a device that transmits radio waves so that wireless LAN users within the transmission distance can access the Internet and use the network, and acts as a base station of a mobile phone or a hub of a wired network. In the wireless high-speed Internet service provided by ISP (Internet Service Provider), AP equipment is already installed in the service area.

The terminal must be equipped with a wireless LAN card or the like in order to perform wireless network communication, and may include a PC (including a laptop), a cellular phone, or a PDA.

The most widely used wireless LAN standard today is IEEE 802.11, and the IEEE 802.11 standard defines regulations on the physical layer and medium access control constituting the wireless LAN.

The media access control layer makes efficient use of media capacity by defining an order and rules to be followed when a terminal or device using a shared media uses/accesses the media.

The basic building block of the IEEE 802.11 network is a basic service set (hereinafter referred to as "BSS"). The IEEE 802.11 network includes an independent BSS, in which terminals within the BSS communicate directly with each other, and an infrastructure network (Infrastructure BSS) and BSS in which an AP intervenes in the process of communicating with terminals within and outside the BSS. There is an extended service set that extends the service area by connecting the BSS.

In general, an IEEE 802.11-based wireless LAN system accesses a medium based on a CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) method, and each AP (Access Point) operates independently of each other. In other words, the wireless LAN system does not allocate a channel by a separate device, and each AP independently selects a channel by an operator or a channel allocation algorithm when the AP is powered on. Therefore, in a situation where many wireless LAN systems exist, there is a high possibility that the channels used by each BSS will overlap. When the channels overlap, interference occurs between adjacent BSSs.

If WLAN communication devices belonging to the same BSS are communicating according to the rules and radiating radio waves irrespective of the rules at a short distance where radio wave emitting devices that do not belong to the same BSS can sufficiently affect, WLAN communication devices will interfere with communication. You will receive.

In the existing interference environment WLAN network, a method of avoiding mutual interference by using CSMA was applied. However, in the CSMA protocol, degrees-of-freedom (DoF) of the entire network is limited to the number of antennas of the AP.

An opportunistic transmission method according to an embodiment includes: broadcasting a random beam; Receiving feedback information determined based on the random beam from a terminal device; Selecting at least one terminal device to transmit data from among the terminal devices based on the feedback information; Adjusting transmission power based on the feedback information; And transmitting data to the at least one selected terminal device based on the adjusted transmission power.

The opportunistic transmission method according to an embodiment may include transmitting a message indicating the start of MU-MIMO communication when selection of a terminal device for all subchannels or all streams is completed.

An opportunistic transmission method according to another embodiment includes the steps of dividing an entire frequency band into a plurality of subchannels; Broadcasting a random beam for each subchannel; Receiving feedback information determined based on the random beam from a plurality of terminal devices; And selecting at least one terminal device to transmit data from among the terminal devices based on the feedback information for each sub-channel.

An opportunistic transmission method according to another embodiment includes: when receiving a random beam from an access point, generating feedback information based on the random beam; Setting a waiting time based on the signal-to-interference noise ratio included in the feedback information; And when feedback information is not received from another terminal device included in the service range of the access point during the waiting time, transmitting the generated feedback information to the access point.

The opportunistic transmission method according to another embodiment may further include resetting the waiting time to infinity when feedback information is received from the other terminal device during the waiting time.

In the opportunistic transmission method according to another embodiment, when a message indicating that the access point has received feedback information from at least one terminal device is received from the access point during the waiting time, the waiting time is infinite. It may further include the step of resetting to.

An access point according to an embodiment includes: a communication unit for broadcasting a random beam and receiving feedback information determined based on the random beam from a terminal device; A terminal device selection unit for selecting at least one terminal device to transmit data from among the terminal devices based on the feedback information; And a transmission power adjusting unit that adjusts transmission power based on the feedback information.

The access point according to an embodiment may further include a frequency band dividing unit for dividing the entire frequency band into a plurality of sub-channels, and the terminal device selection unit may further include the terminal device based on the feedback information for each sub-channel. Among them, at least one terminal device to transmit data may be selected.

A terminal device according to an embodiment includes: a feedback information generator configured to generate feedback information based on the random beam when receiving a random beam from an access point; A waiting time setting unit for setting a waiting time based on the signal-to-interference noise ratio included in the feedback information; And a communication unit that transmits the generated feedback information to the access point when feedback information is not received from another terminal device included in the service range of the access point during the waiting time.

1 is a diagram illustrating an example of an interference environment of a wireless LAN according to an embodiment.
2 is a diagram showing a detailed configuration of an access point according to an embodiment.
3 is a diagram showing a detailed configuration of a terminal device according to an embodiment.
4 is a diagram showing a channel use range of IEEE 802.11ac according to an embodiment.
5 is a flowchart illustrating the overall operation of a method for opportunistic interference alignment according to an embodiment.
6 is a diagram illustrating a protocol for opportunistic interference alignment according to an embodiment.
7 is a diagram illustrating a method of transmitting a clear to send (CTS) message including feedback according to an embodiment.
8 is a flowchart illustrating an operation of an opportunistic interference alignment method performed by an access point according to an embodiment.
9 is a flowchart illustrating an operation of an opportunistic interference alignment method performed in a terminal device according to an embodiment.
10 is a diagram for explaining a method of controlling transmission power based on SINR according to an embodiment.
11 is a diagram for describing a method for controlling transmission power based on LIF according to an embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description to be disclosed hereinafter together with the accompanying drawings is intended to describe exemplary embodiments of the present invention, and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the invention may be practiced without these specific details.

The following embodiments are a combination of components and features of the present invention in a predetermined form. Each component or feature may be considered optional unless otherwise explicitly stated. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, some components and/or features may be combined to constitute an embodiment of the present invention. The order of operations described in the embodiments of the present invention may be changed. Some configurations or features of one embodiment may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

Specific terms used in the following description are provided to aid understanding of the present invention, and the use of these specific terms may be changed in other forms without departing from the technical spirit of the present invention.

In some cases, in order to avoid obscuring the concept of the present invention, well-known structures and devices are omitted, or are shown in block diagram form centering on core functions of each structure and device. In addition, the same components will be described with the same reference numerals throughout the present specification.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the IEEE 802 system, 3GPP system, 3GPP LTE and LTE-A (LTE-Advanced) system, and 3GPP2 system, which are radio access systems. That is, among the embodiments of the present invention, steps or parts not described in order to clearly reveal the technical idea of the present invention may be supported by the above documents. In addition, all terms disclosed in this document can be described by the standard document.

The following technologies are CDMA (Code Division Multiple Access), FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access), SC-FDMA (Single Carrier Frequency Division Multiple Access), etc. It can be used in a variety of wireless access systems. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with radio technologies such as Global System for Mobile communications (GSM)/General Packet Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented with a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and E-UTRA (Evolved UTRA). For clarity, the following description focuses on the IEEE 802.11 system, but the technical idea of the present invention is not limited thereto.

When using Interference Alignment (IA) in WLAN, degrees-of-freedom (DoF) over the entire network is achieved by mapping the interfering signals received by each receiving end of the interfering network into a space having a limited dimension. It can be increased in proportion to the number of interfering access points (APs), and finally, the sum-rate of the network environment can be increased.

Interference alignment can be implemented using various aspects of diversity. In the Opportunistic Interference Alignment (OIA) method of interference alignment, the use of multiuser diversity is used to provide a transmission opportunity to the terminal devices with the best interference alignment among many terminal devices. Thus, the DoF of the entire network can be improved. Opportunistic interference alignment is a method of aligning and transmitting a signal of a terminal device having a high priority so that an interference signal of a terminal device having a low priority does not affect the signal. In the case of opportunistic interference alignment, since only the terminal devices with the best interference alignment need to be found, interference alignment can be implemented with only a small feedback overhead according to a protocol design method.

Hereinafter, for convenience of explanation, the following items are assumed. However, the scope of the present invention should not be construed as limited by the following assumptions.

(i) It is assumed that the channel between an access point (AP) and a terminal device (or a station (STA)) is the same for an uplink and a downlink. That is, it is assumed that there is channel reciprocity.

(ii) It is assumed that each terminal device having a transmission opportunity can receive one symbol stream service from the AP at the same time. The terminal device may correspond to the user.

(iii) The terminal device checks information on a transmission vector space designated by the AP, and calculates an expected Signal to Interference plus Noise Ratio (SINR) using the information on the transmission vector space. I assume you can. In addition, it is assumed that the terminal device can calculate a leakage of interference (LIF) due to interference from other APs and inter-user interference (IUI) in the same AP network. The transmission vector space may include information on a signal vector used by the access point for transmission. The LIF may indicate how deep the channels between terminal devices are in a deep fade. The AP may control signal transmission power of the MU-MIMO system using SINR information and LIF information of the terminal device.

(iv) Since feedback information is temporally separated and transmitted in an interfering network, it is assumed that each AP can receive both the feedback information of the network to which it belongs and other interfering networks.

(v) It is assumed that the noise variance follows Equation 1 below.

는 AP 네트워크 g에 속한 단말 장치 a에서의 노이즈 벡터(noise vector)를 나타낸다. E는 에너지를 나타내고, H는 채널 매트릭스(channel matrix)를 나타낸다.In Equation 1,

Denotes a noise vector in the terminal device a belonging to the AP network g. E denotes energy, and H denotes a channel matrix.

1 is a diagram illustrating an example of an interference environment of a wireless LAN according to an embodiment.

In the wireless transmission environment shown in FIG. 1, it is assumed that the number of APs is 2, the number of terminal devices (STAs) per AP network is 3, the number of antennas of each AP is 4, and the number of antennas of the terminal devices is 3.

Each AP has multiple antennas, and a terminal device may have multiple antennas. In WLAN, multiple terminal devices can access each AP network, and each terminal device can receive a downlink message symbol through an AP of the AP network to which it belongs.

Each terminal device may use a plurality of antennas (multi-antenna) in the process of receiving a message symbol in order to reduce the effect of interference by other AP networks. The terminal device can reduce the influence of interference in a symbol decoding process by using a plurality of antennas.

In a wireless interference channel environment, a plurality of terminal devices may transmit and receive each other and receive not only a desired signal but also an interference signal. In a radio interference channel environment, when an AP transmits signals to terminal devices of an AP network to which it belongs, a signal received from each terminal device may be expressed as Equation 2 below.

는 AP 네트워크 g의 단말 장치

에서 수신한 신호 벡터를 나타내고,

는 단말 장치

와 AP

간의 무선 채널 매트릭스,

는 AP 네트워크 g에서의 s 번째 심볼 스트림을 위한 전송 벡터(transmission vector),

는 AP 네트워크 g에 속하는 단말 장치

에서의 백색 가우시안 잡음(white Gaussian noise)를 나타낸다. 여기서,

는 AP 네트워크 g에서 s 번째 심볼 스트림에 대해 수신 기회를 얻은 단말 장치를 나타낸다.In Equation 2,

The terminal device of the AP network g

Represents the signal vector received at,

The terminal device

And AP

Wireless channel matrix between,

Is a transmission vector for the s-th symbol stream in the AP network g,

Is a terminal device belonging to the AP network g

Represents white Gaussian noise at. here,

Represents a terminal device that has obtained a reception opportunity for the s-th symbol stream in the AP network g.

Interference Environment When message symbol transmission of each AP network occurs at the same time in a multi-AP network, throughput of the entire network may decrease due to interference. Appropriate interference coordination is required to prevent degradation of throughput due to interference.

In the case of downlink MU-MIMO-based interference coordination using opportunistic interference alignment (OIA), a decrease in throughput due to interference can be prevented by selecting a terminal device that is affected by the least interference from other AP networks in each AP. In opportunistic interference alignment, when the terminal device receives information on a transmission vector space from all APs, the terminal device calculates an expected SINR value for each message symbol stream using the information on the received transmission vector space. You can decide. In this case, the SINR value that the terminal device can expect for each symbol stream may be expressed as Equation 3 below.

는 AP 네트워크 g에 속한 단말 장치 a에서 s 번째 메시지 심볼 스트림을 디코딩할 경우의 SINR을 나타낸다.

는 AP 네트워크 g의 단말 장치 a에서 s 번째 심볼 스트림에 의해 메시지를 전송 받을 경우 사용할 수 있는 수신 벡터(receive vector)를 나타낸다.

는 Zero-Forcing 또는 MMSE(minimum mean square error)에 기초하여 각 단말 장치에서 계산될 수 있다.

는 AP 네트워크 g에 속한 단말 장치 a에서의 노이즈 벡터를 나타내고,

는 AP 네트워크 g에 속한 단말 장치 l과 AP

간의 채널 매트릭스를 나타낸다.

는 AP 네트워크 g에 속한 단말 장치 l과 AP g 간의 채널 매트릭스를 나타내고,

는 AP 네트워크 g에 속한 단말 장치 a와 AP g 간의 채널 매트릭스를 나타낸다.

는 AP 네트워크 k에서의 l 번째 MU-MIMO 전송을 위해 각 단말 장치에 전송되는 초기 벡터를 나타내고,

은 AP 네트워크 g에서의 l 번째 MU-MIMO 전송을 위해 각 단말 장치에 전송되는 초기 벡터를 나타낸다.

는 AP 네트워크 g에서의 s 번째 MU-MIMO 전송을 위해 각 단말 장치에 전송되는 초기 벡터를 나타낸다.In Equation 3

Denotes SINR when the terminal device a belonging to the AP network g decodes the s-th message symbol stream.

Denotes a reception vector that can be used when the terminal device a of the AP network g receives a message through the s-th symbol stream.

May be calculated in each terminal device based on Zero-Forcing or MMSE (minimum mean square error).

Denotes a noise vector in the terminal device a belonging to the AP network g,

Is the terminal device l and AP belonging to the AP network g

It represents the channel matrix between.

Denotes a channel matrix between the terminal device l and the AP g belonging to the AP network g,

Represents a channel matrix between the terminal device a and the AP g belonging to the AP network g.

Represents an initial vector transmitted to each terminal device for the l th MU-MIMO transmission in AP network k,

Represents an initial vector transmitted to each terminal device for the l th MU-MIMO transmission in the AP network g.

Represents an initial vector transmitted to each terminal device for the s-th MU-MIMO transmission in the AP network g.

The power affected by the LIF in each terminal device may be estimated based on Equation 4 below.

는 AP 네트워크 g에 속한 단말 장치 a에서 s 번째 심볼 스트림을 디코딩할 경우, 다른 AP 네트워크로부터의 간섭 및 IUI(inter-user interference)의 디코딩 후의 잔여 전력을 나타낸다.

는 AP 네트워크 g의 단말 장치 a에서 s 번째 심볼 스트림에 의해 메시지를 전송 받을 경우 사용할 수 있는 수신 벡터를 나타낸다.

는 AP 네트워크 g에 속한 단말 장치 l과 AP

간의 채널 매트릭스를 나타내고,

는 AP 네트워크 g에 속한 단말 장치 l과 AP g 간의 채널 매트릭스를 나타낸다.

는 AP 네트워크 k에서의 l 번째 MU-MIMO 전송을 위해 각 단말 장치에 전송되는 초기 벡터를 나타내고,

은 AP 네트워크 g에서의 l 번째 MU-MIMO 전송을 위해 각 단말 장치에 전송되는 초기 벡터를 나타낸다In Equation 4,

Denotes interference from other AP networks and residual power after decoding of inter-user interference (IUI) when the terminal device a belonging to the AP network g decodes the s-th symbol stream.

Denotes a reception vector that can be used when the terminal device a of the AP network g receives a message through the s-th symbol stream.

Is the terminal device l and AP belonging to the AP network g

Represents the channel matrix between,

Denotes a channel matrix between the terminal device l and the AP g belonging to the AP network g.

Represents an initial vector transmitted to each terminal device for the l th MU-MIMO transmission in AP network k,

Represents the initial vector transmitted to each terminal device for the l th MU-MIMO transmission in the AP network g

In the opportunistic interference alignment-based protocol, a terminal device having the highest SINR obtains an opportunity to receive a message symbol, thereby minimizing the influence of interference between each AP network. In this case, each AP may select a terminal device using SINR information of the terminal device, and may perform power control using SINR and LIF. Higher transmission efficiency can be obtained by performing power control.

2 is a diagram showing a detailed configuration of an access point 210 according to an embodiment.

The access point 210 may increase a transmission rate by using opportunistic interference alignment in a MU-MIMO system in which a plurality of terminal devices interfere with each other. The access point 210 may broadcast a random beam and opportunistically select a terminal device to communicate with the access point 210 from among a plurality of terminal devices.

Referring to FIG. 2, the access point 210 may include a communication unit 230, a terminal device selection unit 240, and a transmission power adjustment unit 250.

The communication unit 230 may broadcast a random beam. For example, the communication unit 230 may randomly select a transmission vector space and broadcast information on the selected transmission vector space to a plurality of terminal devices. The communication unit 230 may randomly generate unit vectors orthogonal to each other, and may broadcast the generated unit vectors to a plurality of terminal devices. The communication unit 230 may select and broadcast a set of random orthogonal random beams.

The communication unit 230 may receive feedback information from a terminal device. The terminal device may determine feedback information based on the random beam received from the access point 210. The feedback information may include information on at least one of a signal-to-interference noise ratio and an interference leakage calculated by the terminal device. The interference leakage may include information on interference by other terminal devices in the service area of the access point 210 and interference by other access points.

When receiving feedback information from a terminal device, the communication unit 230 may transmit an acknowledgment (ACK) message indicating that the feedback information has been received. After receiving the CTS message related to the feedback information from the terminal device, the communication unit 230 may transmit an ACK message for a corresponding subchannel or stream.

The terminal device selection unit 240 may select at least one terminal device to transmit data from among a plurality of terminal devices based on feedback information received from the terminal device. The terminal device selection unit 240 may select a terminal device to receive data for each subchannel or each stream based on the feedback information.

The terminal device selection unit 240 may select a terminal device that receives the least interference from another network. The terminal device selection unit 240 may select at least one terminal device to transmit data from among the terminal devices based on the magnitude of the signal-to-interference noise ratio included in the feedback information. For example, the terminal device selection unit 240 may select a terminal device having the highest signal-to-interference noise ratio among signal-to-interference noise ratios of the terminal devices. The terminal device selection unit 240 may select a terminal device that transmits the CTS message fastest for each beam as a terminal device to transmit data. When receiving the CTS message, the communication unit 230 may transmit an ACK message so that other terminal devices do not transmit a CTS message for a corresponding beam.

The transmission power adjustment unit 250 may adjust transmission power based on the feedback information in order to obtain higher transmission efficiency. The transmission power controller 250 may adjust the transmission power by using at least one of a signal-to-interference noise ratio and an interference leakage included in the feedback information.

According to an embodiment, the transmission power controller 250 may adjust the transmission power based on the signal-to-interference noise ratio received from the terminal device. The transmission power controller 250 may control transmission power for each stream in consideration of fairness of signal-to-interference noise ratios of terminal devices. The transmission power adjustment unit 250 may reduce transmission power based on the lowest signal-to-interference noise ratio among the signal-to-interference noise ratios of at least one terminal device selected by the terminal device selection unit 240.

According to another embodiment, the transmission power controller 250 may adjust the transmission power based on the interference leakage value. The transmission power adjustment unit 250 determines an average interference leakage value based on the interference leakage values of a plurality of terminal devices, and the interference leakage value and the determined average interference of at least one terminal device selected by the terminal device selection unit 240 The transmit power can be adjusted based on the leakage value. The transmission power controller 250 may know the effect of interference in the entire network by using the interference leakage value received from the terminal devices. The transmission power controller 250 may know the relative effect of the interference leakage received by terminal devices for each stream based on the average interference leakage value.

According to another embodiment, the transmission power controller 250 may adjust the transmission power by using both the signal-to-interference noise ratio and interference leakage information. The transmission power control unit 250 is based on the lowest signal-to-interference noise ratio among the signal-to-interference noise ratios of at least one terminal device selected by the terminal device selection unit 240 and an average interference leakage value determined based on the interference leakage values of the terminal devices. Thus, the transmission power can be adjusted.

The communication unit 230 may broadcast information on the selected terminal device. The communication unit 230 may transmit data to at least one terminal device selected by the terminal device selection unit 240 on the basis of the transmission power adjusted by the transmission power adjustment unit 250. The communication unit 230 may broadcast information on the terminal device selected by the terminal device selection unit 240 when negotiation of the control message for the entire frequency band or stream is terminated.

When the selection of the terminal device for all sub-channels or all streams is completed, the communication unit 230 may transmit a message indicating the start of multi-user multi-input multi-output (MU-MIMO) communication. The communication unit 230 may transmit a message indicating the start of MU-MIMO communication, including information on a terminal device selected for each beam.

According to another embodiment, the access point 210 may further include a frequency band division unit 220.

The frequency band divider 220 may divide the entire frequency band into a plurality of sub-channels. In this case, the communication unit 230 may broadcast a random beam for each sub-channel. In addition, the terminal device selection unit 240 may select at least one terminal device to transmit data from among the terminal devices based on feedback information for each sub-channel.

3 is a diagram showing a detailed configuration of a terminal device 310 according to an embodiment.

Referring to FIG. 3, the terminal device 310 may include a feedback information generation unit 320, a waiting time setting unit 330, and a communication unit 340.

The communication unit 340 may receive a random beam from an access point. The communication unit 340 may receive information on a transmission vector space or information on an arbitrary orthogonal random beam from the access point.

The feedback information generator 320 may generate feedback information based on a random beam received from an access point. The feedback information generator 320 may determine an expected signal-to-interference noise ratio for each stream. For example, the feedback information generator 320 may determine a signal-to-interference noise ratio based on an orthogonal random beam received from an access point.

The feedback information generator 320 may check information on a transmission vector space designated by an access point, and determine an expected signal-to-interference noise ratio using the information on the transmission vector space. The feedback information generator 320 may determine an expected signal-to-interference noise ratio for each message symbol stream by using information on the transmission vector space received from all access points.

The feedback information generator 320 may determine an interference leakage (LIF) due to interference from another access point and interference from other terminal devices within a service range of the same access point. The feedback information generator 320 may determine an expected amount of interference leakage during signal decoding. The feedback information generator 320 may generate information on a signal-to-interference noise ratio and interference leakage as feedback information.

The waiting time setting unit 330 may set the waiting time based on the signal-to-interference noise ratio included in the feedback information. For example, the waiting time setting unit 330 may set the waiting time to be in inverse proportion to the magnitude of the signal-to-interference noise ratio.

According to an embodiment, when receiving feedback information from another terminal device during the waiting time, the waiting time setting unit 330 may reset the waiting time to infinity. According to another embodiment, when receiving a message indicating that the access point has received feedback information from at least one terminal device during the waiting time, the waiting time setting unit 330 may reset the waiting time to infinity. have.

When the communication unit 340 receives a CTS message related to feedback information from other terminal devices included in the same network or an ACK message indicating that feedback information has been received from an access point, the corresponding subchannel accesses the CTS message during the transmission time. Do not send to the point.

The terminal device 310 may determine whether it is possible to obtain a transmission opportunity for each subchannel or stream through a CTS message related to feedback information from other terminal devices or an ACK message indicating that feedback information has been received from an access point. . The terminal device 310 may prevent flooding of a control message by not transmitting a CTS message to an access point for a stream that has already been negotiated.

When the communication unit 340 does not receive feedback information from another terminal device included in the service range of the access point during the waiting time set by the waiting time setting unit 330, the feedback generated by the feedback information generation unit 320 Information can be transmitted to the access point. The communication unit 340 may transmit a clear-to-send (CTS) message and feedback information to the access point. The communication unit 340 may transmit feedback information for each sub-channel or stream. The communication unit 340 may distinguish and transmit the CTS message for each sub-channel or stream. When transmitting the CTS message, the communication unit 340 may transmit information on a beam index, a signal-to-interference noise ratio, and interference leakage as feedback information.

The access point may select a terminal device to transmit data based on the signal-to-interference noise ratio information received from the terminal device 310. The access point may adjust the transmit power based on the signal-to-interference noise ratio and feedback information about interference leakage. The access point may transmit data to the selected terminal device based on the adjusted transmit power.

4 is a diagram showing a channel use range of IEEE 802.11ac according to an embodiment.

In the case of IEEE 802.11ac, up to 160 MHz can be used, and it may be inefficient due to frequency selectivity for one terminal device to simultaneously use all channels due to a wide bandwidth. Therefore, it is preferable that the AP divides the entire band into several sub-channels and performs OIA-based adjustment. There are two main advantages when OIA is adjusted by dividing the entire frequency band for each sub-channel.

First, the effect of multiuser diversity can be obtained. When the entire frequency band is secured and used by only one terminal device, in general, there may be a frequency section in which deep fading occurs in a channel between the terminal device and an AP communicating with the terminal device. In the frequency section where deep fading occurs, it may be difficult to expect an overall throughput improvement due to low SINR. In addition, a frequency section in which deep fading occurs may cause a strong interference level in a specific frequency band in terms of an interfering link. In this case, throughput may be degraded in a specific frequency band due to interference transmitted from other networks. In implementing the opportunistic interference alignment protocol (OIA protocol), when the terminal device selection is performed for each sub-channel by dividing it into sub-channels, the possibility of preventing a deep fading effect or a strong interference effect is increased depending on the number of terminal devices. , This can lead to an increase in the throughput of the overall network.

Second, it has the advantage that it is easy to perform opportunistic interference alignment adjustment (OIA coordination) at the same time while protecting the communication of IEEE 802.11a in terms of backward compatibility. In the case of performing opportunistic interference alignment adjustment by dividing the entire frequency band into several subchannels, it is easy to adjust the opportunistic interference alignment without any restrictions in a subchannel that is not used by terminal devices of IEEE 802.11a.

In the subchannel where the existing IEEE 802.11a terminal device communicates, the existing IEEE 802.11a terminal device and the IEEE 802.11ac terminal device coexist with each other through the RTS (request to send)-CTS (clear to send) exchange method, thereby affecting interference. Can be avoided.

5 is a flowchart illustrating the overall operation of a method for opportunistic interference alignment according to an embodiment. 5 is a flowchart illustrating an operation of an opportunistic interference alignment method in downlink (DL) MU-MIMO transmission.

In step 510, the access point may randomly determine a transmission vector space and broadcast the determined transmission vector space to terminal devices.

In step 520, the terminal device may calculate the expected SINR and LIF for each stream, and calculate an optimal reception vector.

In step 530, the terminal device may transmit a CTS message including SINR and LIF to the access point. The waiting time for feedback may be determined by the inverse of SINR.

In step 540, the access point may receive a CTS message from the terminal device and select a terminal device having optimal performance based on the SINR. For example, the access point may select a terminal device having the highest SINR.

In step 550, the access point may calculate a power adjustment condition based on at least one of SINR and LIF. The access point may perform power adjustment based on feedback information such as SINR and LIF received from the terminal device. Through power adjustment, a higher throughput can be obtained compared to the transmitted power.

In step 560, the access point may broadcast information on the terminal device selected in step 540 to the terminal device.

In step 570, the access point may transmit the message symbol to the terminal device selected in step 540 using MU-MIMO.

6 is a diagram illustrating a protocol for opportunistic interference alignment according to an embodiment.

In step 610, the AP may broadcast a transmission vector space to terminal devices. The AP must designate a signal vector that it uses for data transmission.

In step 620, the terminal devices may calculate an optimal reception vector and calculate SINR and LIF for each stream. Terminal devices may calculate an expected level of remaining interference after combining the reception vectors for each stream.

인 경우, 해당 스트림에 대한 피드백을 포함하는 CTS 메시지를 전송하기 위해 AP의 시스템 파라미터의 브로드캐스트 이후의 대기 시간은

에 의해 계산될 수 있다. 여기서, T_c는 미리 설정된 상수이다.

의 시간 동안 같은 네트워크에 속한 다른 단말 장치들이 스트림 s에 대한 피드백을 전송하지 않을 경우, 단말 장치 a는 해당 스트림에 대해 피드백을 전송할 수 있다. AP는 CTS 메시지를 받은 이후에, 해당 서브 채널 및 스트림에 대한 ACK(acknowledgement) 메시지 또는 CTS 메시지를 다른 단말 장치로부터 수신하는 경우, 해당 서브 채널에 대해서는 해당 통신 구간 동안 CTS 메시지를 송신하지 않는다. In step 630, the terminal devices may feed back the SINR and LIF for each stream to the AP. The time the terminal device waits to transmit the control message may be in inverse proportion to the level of the SINR. For example, the SINR corresponding to the subchannel f and stream s of the terminal device a belonging to the AP network g

In the case of, the waiting time after the broadcast of the system parameters of the AP in order to transmit the CTS message including the feedback for the corresponding stream is

Can be calculated by Here, T _c is a preset constant.

If other terminal devices belonging to the same network do not transmit the feedback for the stream s during the time of, the terminal device a may transmit the feedback for the corresponding stream. After receiving the CTS message, when the AP receives an acknowledgment (ACK) message or a CTS message for the corresponding subchannel and stream from another terminal device, the AP does not transmit the CTS message for the corresponding subchannel during the corresponding communication period.

In step 640, the AP may select a terminal device based on the SINR for each stream. The AP may select a terminal device that can receive data service for each subchannel and symbol stream according to the SINR level of the terminal device.

In an interference coordination process using opportunistic interference alignment, since the AP only needs to identify terminal devices having a low LIF level, it is not necessary to receive LIF values from all terminal devices. In the process of control message negotiation for data transmission, if the terminal device with the highest SINR has the highest priority in transmitting CTS messages and feedback, the terminal device with the high SINR transmits the feedback within the fastest time. I can. Accordingly, when feedback for a corresponding stream is prohibited to other terminal devices after one feedback is transmitted for one sub-channel and stream, it is possible to naturally reduce a feedback duration and overhead. The AP can reduce control message overhead for opportunistic interference alignment through CTS scheduling using the SINR level.

In step 650, the AP may adjust the transmit power. The AP may control the transmission power based on the level of SINR and LIF. In order to allocate a reception opportunity to a terminal device for each subchannel and stream, the CTS message needs to be transmitted separately for each subchannel and stream. The AP may improve throughput versus transmit power by controlling the transmit power based on the level of SINR and LIF, which may lead to an increase in battery life of the terminal device. In addition, the reduced transmission power can reduce the influence of interference to other networks that are not subjected to interference coordination.

In step 660, the AP may broadcast information on the terminal device selected in step 640. When negotiation of control messages for the entire frequency band and stream is finished, the AP may broadcast information on users selected for opportunistic transmission. Terminal devices may receive message symbols from the AP through corresponding subchannels and streams.

In step 670, the AP may transmit the message symbol to the terminal device selected in step 640 using MU-MIMO.

7 is a diagram illustrating a method of transmitting a clear to send (CTS) message including feedback according to an embodiment.

7 shows a transmission process of a CTS message for each stream when there are a plurality of terminal devices (or stations, STAs). Each station can determine a waiting time of expectation before transmitting a CTS message for each stream with a common constant and in inverse proportion to the initial SINR. If one station transmits the CTS message at the earliest time for the corresponding stream, it can be determined that the SINR of the corresponding station is the highest, and it can be considered that interference alignment is best performed in the transmission vector spaces determined by each AP. . Accordingly, when one station transmits a CTS message for one stream, stations on the same network do not additionally transmit a CTS message to the AP.

8 is a flowchart illustrating an operation of an opportunistic interference alignment method performed by an access point according to an embodiment.

In step 810, the AP may broadcast a random beam. The AP may randomly select a transmission vector space and broadcast the selected transmission vector space. The AP may randomly generate unit vectors orthogonal to each other, and may broadcast the generated unit vectors to a plurality of terminal devices. The AP may broadcast a vector space for randomly transmitting messages to terminal devices. The AP may select and broadcast a set of random orthogonal random beams.

According to another embodiment, the AP may divide the entire frequency band into a plurality of subchannels before broadcasting the random beam. Thereafter, the AP broadcasts a random beam for each subchannel and may select a terminal device for each subchannel.

In step 820, the AP may wait until it receives feedback information (or CTS message) from terminal devices.

In step 830, the AP may determine whether the received CTS message is transmitted to the target itself. The AP may receive a CTS message including feedback information for each sub-channel and stream.

If the received CTS message targets itself, in step 840, the AP selects a terminal device for opportunistic transmission and may transmit an ACK signal. In addition, when receiving feedback information from the terminal device, the AP may transmit an ACK message indicating that the feedback information has been received. The AP may select a terminal device for each stream using feedback information received from the terminal devices. The AP may select a terminal device to receive data for each sub-channel or each stream based on the feedback information.

The AP may select a terminal device that receives the least interference from other networks. The AP may select at least one terminal device to transmit data from among the terminal devices based on the magnitude of the signal-to-interference noise ratio included in the feedback information. For example, the AP may select a terminal device having the highest signal-to-interference noise ratio among the signal-to-interference noise ratios of the terminal devices.

In step 850, the AP may determine whether a terminal device has been selected for all streams.

When the terminal device is selected for all streams, in step 860, the AP may adjust the transmission power for each stream. The AP may adjust transmission power using at least one of a signal-to-interference noise ratio and interference leakage included in the feedback information.

For example, the AP may reduce the transmission power based on the lowest signal-to-interference noise ratio among the signal-to-interference noise ratios of at least one terminal device selected by the terminal device selection unit. As another example, the AP determines an average interference leakage value based on the interference leakage values of a plurality of terminal devices, and transmits based on the interference leakage value and the determined average interference leakage value of at least one terminal device selected by the terminal device selection unit. Power can be adjusted. As another example, the AP may adjust the transmission power using both the signal-to-interference noise ratio and interference leakage information.

In step 870, the AP may broadcast information on the selected terminal device. After the control message negotiation step, the AP broadcasts information on the selected terminal devices, so that the AP may notify the terminal device that all control message negotiations have ended and that it has entered the communication phase. When the selection of the terminal device for all subchannels or all streams is completed, the AP may transmit a message indicating the start of MU-MIMO communication.

In step 880, the AP may transmit a message using MU-MIMO. The AP may transmit data to the selected terminal device based on the adjusted transmit power.

9 is a flowchart illustrating an operation of an opportunistic interference alignment method performed by a terminal device according to an embodiment.

In step 910, the terminal device may wait until a random beam is received from the AP. The terminal device may wait until the AP receives transmission vector spatial information designated by the AP or information on a random orthogonal random beam.

In step 920, the terminal device may generate feedback information based on the received random beam. For example, the terminal device may calculate the waiting time, SINR, and LIFs for each stream. The terminal device may determine an expected signal-to-interference noise ratio for each stream. For example, the terminal device may determine a signal-to-interference noise ratio based on an orthogonal random beam received from an access point.

The terminal device may check information on a transmission vector space designated by the access point and determine an expected signal-to-interference noise ratio using the information on the transmission vector space. The terminal device may determine an expected signal-to-interference noise ratio for each message symbol stream using information on the transmission vector space received from all access points.

The terminal device may determine an interference leak (LIF) due to interference from another access point and interference from another terminal device within a service range of the same access point. The terminal device may determine an expected amount of interference leakage during signal decoding. The terminal device may generate information on a signal-to-interference noise ratio and interference leakage as feedback information.

In step 930, the terminal device may set a waiting time based on the SINR. For example, the terminal device may set the waiting time in inverse proportion to the magnitude of the signal-to-interference noise ratio.

In step 940, the terminal device may wait for a waiting time for each stream.

In step 945, the terminal device may determine whether or not a CTS message related to the feedback information has been received from another terminal device.

When the terminal device receives the CTS message, in step 950, the terminal device may determine whether the received CTS message is transmitted from another terminal device within the same network. The terminal device may identify whether a transmission opportunity for each sub-channel and stream can be obtained through an ACK message of an AP or a CTS message of another terminal device.

If the received CTS message is transmitted from another terminal device in the same network, in step 960, the terminal device may reset the waiting time for the corresponding stream to infinity. The terminal device can prevent flooding of a control message by not sending a CTS message for a stream that has already been negotiated (a waiting time for a corresponding stream is set to infinite).

Returning to step 945, when the terminal device has not received the CTS message, in step 965, the terminal device may determine whether or not a broadcast message has been received from the AP.

When receiving a broadcast message from the AP, in step 980, the terminal device receives the MU-MIMO signal from the AP, and when the received MU-MIMO signal is intended for itself, the terminal device receives the received MU-MIMO signal. Can be decoded.

Returning to step 965, when the terminal device has not received a broadcast message from the AP, in step 970, the terminal device may transmit a CTS message for a corresponding subchannel to the AP. The CTS message may include feedback information determined by the terminal device.

The AP can adjust the transmission power using only limited feedback information. The AP may adjust the transmission power using only SINR information of the terminal devices or information on the amount of residual LIF after interference cancellation at the terminal device end. FIG. 10 is a diagram for explaining that the AP adjusts transmission power using SINR information of terminal devices, and FIG. 11 is a diagram for explaining that the AP adjusts transmission power using information on the amount of residual LIF.

10 is a diagram for explaining a method of controlling transmission power based on SINR according to an embodiment.

In the case of the SINR-based transmission power control method, the AP may control the transmission power for each stream in consideration of the SINR fairness of terminal devices. When each AP selects terminal devices for each stream, each of the selected terminal devices has different SINR values. In this case, when power adjustment is performed using a given SINR value, a higher throughput compared to the transmission power can be obtained.

Each selected terminal device has a different SINR value, and in order to consider the fairness of the terminal device, the power of each terminal device is reduced based on the lowest SINR among the selected terminal devices.

For example, the access point may adjust the transmission power based on Equation 5 below.

는 AP 네트워크 g에서 s 번째 스트림에 대해 결정된 SINR 기반 전송 전력 조절 컴포넌트이다.

는 선택된 단말 장치들의 SINR 최대값들 중 가장 작은 값을 나타내고,

는 AP 네트워크 g에서 s 번째 스트림에 대해 선택된 단말 장치의 SINR 최대 값을 나타낸다.In Equation 5,

Is an SINR-based transmit power adjustment component determined for the s-th stream in the AP network g.

Represents the smallest value among SINR maximum values of the selected terminal devices,

Represents the maximum SINR value of the terminal device selected for the s-th stream in the AP network g.

과 같이 주어지고, SINR 값이 높을수록 데이터 레이트의 감소가 작아질 수 있다. 즉, 높은 SINR 영역의 단말 장치에서 일어나는 데이터 레이트의 감소가 낮은 SINR 영역의 단말 장치에서 일어나는 데이터 레이트 증가에 비해 작아지게 되고, 최종적으로는 전체 네트워크의 처리량이 증가할 수 있다.By reducing the power transmitted to each terminal device, the level of interference can be reduced. Accordingly, terminal devices having a low SINR can greatly increase the throughput that can be achieved due to the effect of reduced interference. On the other hand, terminal devices having a high SINR may slightly reduce the data rate due to reduced transmission power. However, the typical achievable throughput is

And the higher the SINR value, the smaller the decrease in the data rate may be. That is, the decrease in the data rate occurring in the terminal device in the high SINR region becomes smaller than the increase in the data rate occurring in the terminal device in the low SINR region, and finally, the throughput of the entire network may increase.

11 is a diagram for describing a method for controlling transmission power based on LIF according to an embodiment.

In the case of the LIF-based transmission power control method, the AP analyzes the LIF of each terminal device and, based on this, reduces the transmission power for a stream having a large interference effect, thereby improving overall throughput.

11 shows the interference effect of each terminal device. The influence of the LIF received by each terminal device can be expressed as Equation 6 below.

는 AP 네트워크 g에 속한 단말 장치 d와 AP g 간의 채널 매트릭스를 나타내고,

는 AP 네트워크 g에 속한 단말 장치 d와 AP k 간의 채널 매트릭스를 나타낸다.

는 AP 네트워크 g에서 스트림 s에 대해 선택된 단말 장치를 나타낸다

Denotes a channel matrix between the terminal device d and the AP g belonging to the AP network g,

Represents a channel matrix between the terminal device d and the AP k belonging to the AP network g.

Represents the terminal device selected for stream s in the AP network g

Using Equation 6, each terminal device can calculate the LIF level that it receives. Each terminal device may include and transmit LIF level information calculated when transmitting the CTS message to the AP as feedback information. The AP may identify the degree of interference in the entire network by using the LIF level information received from each terminal device. The value of the averaged LIF level can be expressed as Equation 7 below.

는 네트워크에서 단말 장치들의 간섭 누출 값에 기초하여 결정된 평균 간섭 누출 값이다. K는 전체 네트워크에서 AP의 개수를 나타내고, S는 각 AP당 MU-MIMO 스트림의 개수를 나타낸다.

는 AP 네트워크 g에서 스트림 s에 대해 선택된 단말 장치를 나타낸다.

Is an average interference leakage value determined based on interference leakage values of terminal devices in the network. K represents the number of APs in the entire network, and S represents the number of MU-MIMO streams per AP.

Denotes a terminal device selected for stream s in AP network g.

When the LIF value averaged over the whole is obtained, the relative influence of the LIF received by users for each stream can be known. The AP may perform power adjustment for each stream based on the relative effect of the LIF according to Equation 8 below.

는 AP 네트워크 g에서 스트림 s에 대해 결정된 LIF 기반 전송 전력 조절 컴포넌트이다.

는 네트워크에서 단말 장치들의 간섭 누출 값에 기초하여 결정된 평균 간섭 누출 값이다.

Is an LIF-based transmit power adjustment component determined for stream s in AP network g.

Is an average interference leakage value determined based on interference leakage values of terminal devices in the network.

In Equation 8, when the LIF value of the terminal device is greater than the average value (average interference leakage value) of the LIF for the entire network, it can be understood that the corresponding stream relatively less interferes with transmission of other streams. When the LIF value of the terminal device is larger than the average value of the LIF for the entire network, the AP may reduce power reduction or not perform power reduction for the corresponding stream.

Conversely, when the LIF value of the terminal device is less than the average value of the LIF for the entire network, it can be understood that the corresponding stream has a relatively large influence on transmission of other streams. Accordingly, when the LIF value of the terminal device is less than the average LIF value for the entire network, the AP can adjust the balance of the overall interference influence by increasing the degree of power reduction. Network throughput may be improved by the AP adjusting the transmission power based on the LIF value of the terminal device.

When the SINR-based transmission power control method and the LIF-based transmission power control method are combined, it can be expressed as Equation 9 below.

는 AP 네트워크 g에서 스트림 s에 대해 조절된 전송 전력을 나타내고,

는 조절되기 전의 원래(original) 전송 전력을 나타낸다.

는 AP 네트워크 g에서 s 번째 스트림에 대해 결정된 SINR 기반 전송 전력 조절 컴포넌트이고,

는 AP 네트워크 g에서 스트림 s에 대해 결정된 LIF 기반 전송 전력 조절 컴포넌트이다.

는 선택된 단말 장치들의 SINR 최대값들 중 가장 작은 값을 나타내고,

는 AP 네트워크 g에서 s 번째 스트림에 대해 선택된 단말 장치의 SINR 최대 값을 나타낸다.

는 네트워크에서 단말 장치들의 간섭 누출 값에 기초하여 결정된 평균 간섭 누출 값이다.

Denotes the adjusted transmit power for stream s in the AP network g,

Denotes the original transmit power before being adjusted.

Is the SINR-based transmission power adjustment component determined for the s-th stream in the AP network g,

Is an LIF-based transmit power adjustment component determined for stream s in AP network g.

Represents the smallest value among SINR maximum values of the selected terminal devices,

Represents the maximum SINR value of the terminal device selected for the s-th stream in the AP network g.

Is an average interference leakage value determined based on interference leakage values of terminal devices in the network.

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

As described above, although the embodiments have been described by the limited embodiments and drawings, various modifications and variations are possible from the above description by those of ordinary skill in the art. For example, the described techniques are performed in a different order from the described method, and/or components such as a system, structure, device, circuit, etc. described are combined or combined in a form different from the described method, or other components Alternatively, even if substituted or substituted by an equivalent, an appropriate result can be achieved.

Therefore, other implementations, other embodiments, and claims and equivalents fall within the scope of the claims to be described later.

Claims (27)

In the opportunistic interference alignment method performed by an access point,
Broadcasting a random beam;
Receiving feedback information determined based on the random beam from a terminal device;
Selecting at least one terminal device to transmit data from among the terminal devices based on the feedback information;
Adjusting transmission power based on the feedback information; And
And transmitting data to the selected at least one terminal device based on the adjusted transmission power,
The terminal device,
A waiting time is set based on a Signal to Interference plus Noise Ratio (SINR) included in the feedback information, and during the waiting time, the access point indicates that the access point has received feedback information from another terminal device. When receiving a message indicating, to reset the waiting time to infinity,
Opportunistic interference alignment method. The method of claim 1,
The adjusting step,
Adjusting the transmission power using at least one of a Signal to Interference plus Noise Ratio (SINR) and a Leakage of Interference (LIF) included in the feedback information
Opportunistic interference alignment method comprising a. The method of claim 2,
The adjusting step,
Reducing transmission power based on the lowest signal-to-interference noise ratio among the signal-to-interference noise ratios of the selected at least one terminal device
Opportunistic interference alignment method comprising a. The method of claim 2,
The adjusting step,
Determining an average interference leakage value based on the interference leakage values of the terminal devices; And
Adjusting transmission power based on the interference leakage value and the average interference leakage value of the selected at least one terminal device
Opportunistic interference alignment method comprising a. The method of claim 2,
The adjusting step,
Adjusting the transmission power based on the lowest signal-to-interference noise ratio among the signal-to-interference noise ratios of the selected at least one terminal device and an average interference leakage value determined based on the interference leakage values of the terminal devices
Opportunistic interference alignment method comprising a. The method of claim 1,
The selecting step,
Selecting at least one terminal device to transmit data from among the terminal devices based on the magnitude of the signal-to-interference noise ratio included in the feedback information
Opportunistic interference alignment method comprising a. The method of claim 1,
The selecting step,
Selecting a terminal device to receive data for each sub-channel or each stream based on the feedback information
Opportunistic interference alignment method comprising a. The method of claim 1,
Broadcasting information on the selected terminal device
Opportunistic interference alignment method further comprising. The method of claim 1,
Broadcasting the random beam,
Randomly selecting a transmission vector space; And
Broadcasting information on the selected transmission vector space to a plurality of terminal devices
Opportunistic interference alignment method comprising a. The method of claim 2,
The interference leakage,
Opportunistic interference alignment method including information on interference by other terminal devices and interference by other access points in the service area of the access point. The method of claim 1,
When receiving feedback information from a terminal device, transmitting an acknowledgment (ACK) message indicating that the feedback information has been received
Opportunistic interference alignment method further comprising. The method of claim 1,
Transmitting a message indicating the start of multi-user multi-input multi-output (MU-MIMO) communication when selection of a terminal device for all sub-channels or all streams is completed
Opportunistic interference alignment method further comprising. In the opportunistic interference alignment method performed by an access point,
Dividing the entire frequency band into a plurality of sub-channels;
Broadcasting a random beam for each subchannel;
Receiving feedback information determined based on the random beam from a plurality of terminal devices; And
Selecting at least one terminal device to transmit data from among the terminal devices based on the feedback information for each sub-channel
Including,
The terminal device,
A waiting time is set based on a Signal to Interference plus Noise Ratio (SINR) included in the feedback information, and during the waiting time, the access point indicates that the access point has received feedback information from another terminal device. When receiving a message indicating, to reset the waiting time to infinity,
Opportunistic interference alignment method. In the opportunistic interference alignment method performed by a terminal device,
When receiving a random beam from an access point, generating feedback information based on the random beam;
Setting a waiting time based on the signal-to-interference noise ratio included in the feedback information; And
Transmitting the generated feedback information to the access point when feedback information is not received from another terminal device included in the service range of the access point during the waiting time; And
When receiving feedback information from the other terminal device during the waiting time or when receiving a message indicating that the access point has received feedback information from at least one terminal device from the access point during the waiting time, the waiting time To set to infinity
Opportunistic interference alignment method comprising a. delete delete delete The method of claim 14,
The access point,
Opportunistic interference alignment method, characterized in that the transmission power is adjusted based on the feedback information on the signal-to-interference noise ratio and interference leakage. The method of claim 14,
The transmitting step,
Opportunistic interference alignment method, characterized in that the feedback information is transmitted for each sub-channel or stream. A communication unit that broadcasts a random beam and receives feedback information determined based on the random beam from a terminal device;
A terminal device selection unit for selecting at least one terminal device to transmit data from among the terminal devices based on the feedback information; And
A transmission power adjustment unit that adjusts transmission power based on the feedback information
Including,
The terminal device,
A waiting time is set based on a Signal to Interference plus Noise Ratio (SINR) included in the feedback information, indicating that the access point has received feedback information from another terminal device from the access point during the waiting time. When receiving a message, reset the waiting time to infinity,
Access point. The method of claim 20,
The transmission power control unit,
And adjusting transmission power using at least one of a signal-to-interference noise ratio and interference leakage included in the feedback information. The method of claim 20,
The communication unit,
And transmitting data to the selected at least one terminal device based on the adjusted transmission power. The method of claim 20,
Frequency band division unit that divides the entire frequency band into a plurality of sub-channels
Including more,
And the terminal device selection unit selects at least one terminal device to transmit data from among the terminal devices based on the feedback information for each of the sub-channels. When receiving a random beam from an access point, a feedback information generator for generating feedback information based on the random beam;
A waiting time setting unit for setting a waiting time based on the signal-to-interference noise ratio included in the feedback information; And
Communication unit for transmitting the generated feedback information to the access point when feedback information is not received from another terminal device included in the service range of the access point during the waiting time
Including,
The waiting time setting unit,
A waiting time is set based on a Signal to Interference plus Noise Ratio (SINR) included in the feedback information, and during the waiting time, the access point indicates that the access point has received feedback information from another terminal device. Resetting the waiting time to infinity when receiving a message indicating
Terminal device. The method of claim 24,
The waiting time setting unit,
And setting the waiting time in inverse proportion to the magnitude of the signal-to-interference noise ratio. delete delete

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