KR20220094448A - Apparautus and Method for Downlink Scheduling in OFDM-based Multi-User MIMO System - Google Patents

Abstract

The present invention relates to a multi-user multi-input multi-output down-transmission scheduling device in a local area wireless network and a method thereof. According to an embodiment of the present invention, the OFDM-based multi-user multi-input multi-output down-transmission scheduling device comprises: a communication interface unit communicating with a plurality of peripheral terminals; and a control unit configured to adaptively select and transmit an antenna and a channel bandwidth based on a frame size and a transmission rate of a data stream to be transmitted to the plurality of terminals so as to allow transmission time of each spatial stream of the plurality of terminals to match within the maximum transmission time when the data stream is transmitted to the plurality of terminals through communication.

Description

OFDM-based multi-user multi-input multi-output downlink scheduling apparatus and method for driving the same

The present invention relates to an OFDM-based multi-user multiple-input multiple-output downlink scheduling apparatus and a method of driving the same, and more particularly, to channel aggregation in, for example, DL MU-MIMO (Downlink Multi-User Multiple Input Multiple Output) WLAN ( OFDM-based scheduling technique for channel aggregation that increases throughput efficiency by adaptively allocating spatial streams having different transmission times according to frame sizes and transmission rates to antennas and bandwidths It relates to a multi-user, multiple-input, multiple-output, downlink scheduling apparatus and a driving method of the same.

In general, in order to use DL MU-MIMO using a 40/80 channel band, one access point (AP) transmits a stream to a plurality of terminals (STA) through an aggregated channel. When all spatial streams are transmitted in the same bandwidth, the transmission time from the AP is determined by the spatial stream that takes the longest to transmit.

The IEEE 802.11ac standard introduces DL MU-MIMO technology. In order to use DL MU-MIMO in the 20 MHz channel band, the AP needs to obtain channel state information (CSI) from the STA before transmitting data. In order to obtain CSI, the AP initializes a sounding feedback sequence for DL MU-MIMO by transmitting (broadcasting) NDPA. The NDPA includes an STA that will first transmit a very high throughput (VHT) compressed beamforming (VCB) frame after receiving the NDP, and STAs to be polled thereafter. When the NDPA transmission from the AP is finished, the VHT NDP frame is transmitted from the AP after a short inter-frame interval (SIFS). Thereafter, the STA corresponding to the first STA information field of the NDPA transmits the VCB frame as a sounding feedback frame. After SIFS, the AP sequentially transmits a beamforming report poll (BRP) to the remaining STAs to receive VCBs from the STAs. When CSI is obtained from the STAs, the AP simultaneously transmits data to the STAs using the DL MU-MIMO technology. Thereafter, block responses (BAs) are sequentially received from the STAs.

Such existing 802.11ac performs DL MU-MIMO transmission without considering data size and modulation coding scheme (MCS). Therefore, when the transmission times of the spatial streams do not match, throughput efficiency may decrease. OFDM-based 802.11ac considers that the AP transmits one data frame through one spatial stream. Then, the data frame may be aggregated or fragmented if the destination is the same or if the data size is too large. Nevertheless, the transmission time of each data frame transmitted simultaneously over multiple spatial streams is generally not the same. In addition, the sequential transmission scheme of CSI and BA may act as a significant overhead for DL MU-MIMO. The total transmission time required for CSI and BA can be expressed as <Equation 1> and <Equation 2>.

In <Equation 1> and <Equation 2>, TNDPA, TNDP, TBRP, TVCB, and TBA are times required to send NDPA, NDP, BRP, VCB, and BA, respectively. x is the number of STAs simultaneously transmitted by the AP.

Of course, there have been many studies related to DL MU-MIMO in the prior art, but there is a problem in that none of the prior art considers OFDM-based channelization for DL MU-MIMO WLAN.

Korean Patent Publication No. 10-1335857 (2013.11.26) Korean Patent Publication No. 10-1965542 (2019.03.28) Korean Patent Publication No. 10-1726864 (2017.04.07) Korean Patent Publication No. 10-1554941 (2015.09.16) Korean Patent Publication No. 10-2015-0134520 (2015.12.02) Korean Patent Publication No. 10-2017-0139583 (2017.12.19) Korean Patent Publication No. 10-2020-0104272 (2020.09.03)

An embodiment of the present invention improves throughput efficiency by adaptively allocating spatial streams having different transmission times according to (data) frame sizes and transmission rates to antennas and bandwidths as a scheduling technique for channel aggregation in, for example, DL MU-MIMO WLANs. An object of the present invention is to provide an OFDM-based multi-user multiple input multiple output downlink scheduling apparatus and a driving method of the same.

An OFDM-based multi-user multiple input multiple output downlink transmission scheduling apparatus according to an embodiment of the present invention includes a communication interface unit that communicates with a plurality of peripheral terminals, and a plurality of terminals when transmitting data streams to a plurality of terminals through the communication. Based on the frame size and transmission rate of the data stream to be transmitted to the terminal, an antenna and a channel bandwidth are adaptively selected and transmitted to match the transmission time of each spatial stream of the plurality of terminals within the maximum transmission time includes a control unit.

The controller may transmit a data stream to the plurality of terminals by dynamically changing a preset number of antennas and channel bandwidths according to time changes based on a frame size and a transmission rate of the data stream.

When the transmission rates are the same, the controller allocates a maximum channel bandwidth to a data stream occupying a maximum transmission time to be transmitted to one of the plurality of terminals, and then allocates the remaining channel bandwidth to data streams of the remaining terminals to transmit the data stream. .

The controller may process a null data packet (NDP) for checking channel state information (CIS) for the plurality of terminals before transmitting each spatial stream to the plurality of terminals.

The controller may transmit beamforming report poll (BRP) frames for receiving frame responses through channel bandwidths respectively allocated to the remaining terminals before transmitting each spatial stream.

The control unit may process the data stream according to a communication standard of IEEE 802.11ac.

In addition, the driving method of an OFDM-based multi-user multiple input multiple output downlink transmission scheduling apparatus according to an embodiment of the present invention includes the steps of: a communication interface unit communicating with a plurality of peripheral terminals; When transmitting a data stream to a terminal, an antenna and a channel bandwidth are adaptively selected and transmitted based on the frame size and transmission rate of the data stream to be transmitted to the plurality of terminals, and the transmission time of each spatial stream of the plurality of terminals is set as the maximum transmission time matching into

The driving method may further include transmitting the data stream to the plurality of terminals by dynamically changing a preset number of antennas and channel bandwidths according to time changes based on the frame size and transmission rate of the data stream. have.

In the driving method, when the transmission rates are the same, a maximum channel bandwidth is allocated to a data stream occupying a maximum transmission time to be transmitted to one of the plurality of terminals, and then the remaining channel bandwidth is allocated to data streams of the remaining terminals to transmit the data stream. It may include further steps.

The driving method may further include processing a null data packet (NDP) for checking channel state information (CIS) for the plurality of terminals before transmitting each spatial stream to the plurality of terminals. .

The processing of the NDP may include transmitting each BRP frame for receiving a frame response through a channel bandwidth allocated to the remaining terminals, respectively, before transmitting each spatial stream.

The communicating may include processing the data stream according to a communication standard of IEEE 802.11ac.

According to an embodiment of the present invention, throughput (or data rate) efficiency for DL MU-MIMO can be improved by adaptively allocating spatial streams to a channel width according to a data size and, for example, an MCS.

In addition, according to an embodiment of the present invention, the AP exchanges CSI and BA with STAs before and after DL MU-MIMO transmission in WLAN, and then overhead due to the control frame can be reduced.

Furthermore, according to an embodiment of the present invention, simultaneous transmission between STAs having strong spatial interference is possible.

1 is a diagram showing a wireless network system according to an embodiment of the present invention;
2 is a diagram for explaining a modified NDPA according to an embodiment of the present invention;
3 is a diagram illustrating an example of performing DL MU-MIMO transmission using an 80 MHz channel bandwidth;
4 is a block diagram illustrating a detailed structure of the wireless LAN device of FIG. 1, and
5 is a flowchart illustrating a driving process of a wireless LAN device according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

1 is a diagram showing a wireless network system according to an embodiment of the present invention, FIG. 2 is a diagram for explaining a modified NDPA according to an embodiment of the present invention, and FIG. 3 is a DL MU- using an 80 MHz channel bandwidth. It is a diagram illustrating an example of performing MIMO transmission.

As shown in Fig. 1, the wireless network system 90 according to the embodiment of the present invention includes a plurality of terminal devices 100, a communication network 110, and some or all of the service providing devices that provide content and the like. , where the communication network 110 may include a wireless LAN device 111 .

Here, "including some or all" means that some components such as a service providing device are omitted to configure the wireless network system 90, or a part or all of the service providing device is a network device constituting the communication network 110 (Example: wireless switching device, etc.) It means that it can be integrated and configured, and it will be described as including all in order to help a sufficient understanding of the invention.

The plurality of terminals 100 includes a user terminal device that communicates with a wireless LAN device 111 such as an access point (AP). A user terminal device is also commonly referred to as a station (STA). The plurality of terminals 100 is a user terminal device, and includes a mobile-based user device such as a laptop computer, a tablet PC, and a smart phone capable of wireless communication. Wireless communication (WLAN) can be performed. As short-distance wireless communication, various communications such as Wi-Fi, Zigbee, Bluetooth, and infrared communication may be possible. The plurality of terminals 100 according to an embodiment of the present invention perform communication according to the IEEE 802.11 standard used in a computer wireless network for a small area called a wireless LAN, that is, Wi-Fi, among others. More precisely, 802.11ac communication for VHT can be performed.

IEEE 802.11ac is one of the revised 802.11 wireless computer networking standards to provide a high-speed local area network (LAN). It supports high bandwidth (80MHz~160MHz) at 5GHz frequency, and supports bandwidth up to 40MHz for compatibility with 802.11n at the same 5GHz frequency. On January 20, 2011, the draft technical specification 0.1 was finalized by the IEEE 802.11 TGac (Task Group for ac). The standard was finalized in late 2012, and the final 802.11 committee was approved in January 2014. According to research data, devices with the 802.11ac specification are expected to become common in 2015 and spread to more than 1 billion devices worldwide. Theoretically, according to this standard, the WLAN speed of multiple terminals is at least 1 Gbit/s, and the maximum single link speed is at least 500 Mbit/s. This is achieved by extending the air interface concepts adopted in 802.11n, including wider radio frequency bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256 QAM). .

As such, IEEE 802.11ac aims to provide gigabit or higher speed in the 5 GHz band. 802.11ac Task Group (TG) has presented DL MU-MIMO and channel aggregation as key technologies for implementing VHT. DL MU-MIMO is a technology that enables one AP to simultaneously transmit different streams to other STAs using the same channel. At that time, the AP having N antennas is capable of transmitting a total of N spatial streams. MU-MIMO can significantly improve network throughput (or transmission rate) performance without collision in WLAN.

As a form of 802.11n evolution, 802.11ac supports 40, 80, 160 MHz and non-contiguous 160 MHz channelization. 40/80 MHz is mandatory and 160 MHz is optional. The 802.11ac STA has two access methods to use the 80 MHz channel band. It is a static 80 MHz and 20/40/80 MHz channel band access scheme. In the static 80 MHz band channel access scheme, the 802.11ac STA attempts channel access until all secondary channels are idle (or idle). On the other hand, in the dynamic 20/40/80 MHz band channel access scheme, even if a part of the secondary channel is busy (or in operation), the STA transmits data through a narrower channel consisting of a 20 or 40 MHz band. This is possible.

The plurality of terminals 100 according to an embodiment of the present invention communicate with the wireless LAN device 111 to transmit data through an uplink and download data through a downlink. When receiving data through downlink, the plurality of terminals 100 receive data according to scheduling for channel aggregation in a DL MU-MIMO WLAN (WLAN) according to an embodiment of the present invention. In other words, in the embodiment of the present invention, spatial streams having different transmission times according to frame sizes and transmission rates (or modulation and coding schemes (MCS)) are adaptively allocated to antennas and bandwidths, thereby DL MU-MIMO increase throughput efficiency for This will be dealt with in more detail later.

The wireless LAN device 111 according to an embodiment of the present invention may be one component constituting the communication network 110 . In other words, it can be seen that the communication network 110 plays the role of an intermediary so that the plurality of terminals 100 can access an external device, for example, a service server that provides various services, and use the service through, for example, the wired or wireless Internet. The communication network 110 includes both wired and wireless communication networks. For example, as the communication network 110 , a wired or wireless Internet network may be used or interlocked. Here, the wired network includes an Internet network such as a cable network or a public telephone network (PSTN), and the wireless communication network includes CDMA, WCDMA, GSM, Evolved Packet Core (EPC), Long Term Evolution (LTE), Wibro network, etc. is meant to include Of course, the communication network 110 according to the embodiment of the present invention is not limited thereto, and may be used, for example, in a cloud computing network under a cloud computing environment, a 5G network, and the like. For example, when the communication network 110 is a wired communication network, the access point in the communication network 110 can connect to a switching center of a telephone company, etc., but in the case of a wireless communication network, it connects to a SGSN or GGSN (Gateway GPRS Support Node) operated by a communication company to access data or by accessing various repeaters such as a Base Transmissive Station (BTS), NodeB, and e-NodeB to process data.

The communication network 110 includes an access point (AP) such as the wireless LAN device 111 according to an embodiment of the present invention. Here, the access point includes a small base station, such as a femto or pico base station, which is often installed in a building. Femto or pico base stations are classified according to the maximum number of accessable terminals 100, etc., in terms of the classification of small base stations. Of course, the access point may include a short-distance communication module for performing short-distance communication such as Zigbee and Wi-Fi with the terminal 100 and the like. The access point may use TCP/IP or Real-Time Streaming Protocol (RTSP) for wireless communication. Here, short-distance communication may be performed in various standards such as Bluetooth, Zigbee, infrared, radio frequency (RF) such as ultra high frequency (UHF) and very high frequency (VHF), and ultra-wideband communication (UWB) in addition to Wi-Fi. Accordingly, the access point can extract the location of the data packet, designate the best communication path for the extracted location, and forward the data packet to the next device, for example, an external device such as a service server, along the designated communication path. The access point may share several lines in a general network environment, and includes, for example, a router, a repeater, and a repeater.

The wireless LAN device 111 according to an embodiment of the present invention may operate as a multi-user multiple input multiple output downlink (DL MU-MIMO) scheduling device in a local area wireless network, for example, as an access point (AP). Wireless LAN communication may be performed with the terminal 100 according to the IEEE 802.11 standard. More precisely, MU-MIMO communication is performed according to the IEEE 802.11ac standard. Here, MU-MIMO means multi-user (MU), multiple input (MI), and multiple output (MO) antennas.

More specifically, in the embodiment of the present invention, a downlink MU-MIMO WLAN environment in which one AP simultaneously transmits streams to multiple STAs in a channel bandwidth of 40, 80, and 160 MHz is considered. It is assumed that the AP has N antennas and the STA has one antenna. Under the above assumptions, the procedure according to the embodiment of the present invention may be performed as follows.

First, as a first step, an AP such as the WLAN device 111 performs a pre-stored (or preset) scheduling algorithm to determine a channel bandwidth required for transmission to each STA.

In more detail, the AP calculates the transmission time of the i-th data frame according to the channel bandwidth index j (step 1-1). This can be expressed as in <Equation 3>.

L _i is the size of the payload of the i-th data frame, and R _i is the data (transmission) rate of the i-th data frame when the channel bandwidth is 20 MHz. B _j is the ratio of Ri to the channel bandwidth index j. The data rate is determined by the MCS. The channel bandwidths are 20, 40, 80, and 160 MHz, and the channel bandwidth index j is 1, 2, 3, and 4. B _j becomes 1, 2.077, 4.5, and 9 according to the bandwidth of 20, 40, 80, and 160 MHz, respectively. The data rates for 40, 80, and 160 MHz are not exactly multiples of 20 MHz due to the presence of guardbands. Therefore, RiBi means a data rate for the channel bandwidth corresponding to the channel index j when the i-th data frame is transmitted.

In addition, the AP finds the I-th data frame occupying the maximum transmission time to the maximum channel bandwidth J (steps 1-2). At that time, the transmission time of the DL MU-MIMO may be expressed as Equation (4).

I indicates the data frame with the maximum transmission time, and M is the number of data frames. When multiple data frames are stored in the AP, M is determined by 1+2 ^J-1 (N-1) and N is the number of antennas of the AP.

을 만족하는 i번째 데이터 프레임을 위한 채널 대역폭 j를 찾는다(1-3 단계).Furthermore, the AP determines whether there is an i-th data frame to be transmitted with a channel bandwidth j smaller than the maximum available channel bandwidth J.

A channel bandwidth j for the i-th data frame that satisfies

Next, the AP calculates the maximum k that satisfies <Equation 5> (steps 1-4).

k is the maximum number of data frames that the AP can transmit at the same time, excluding the data frame with the longest transmission time. j _i is the channel bandwidth index j for the i-th data frame. In this case, the AP having N antennas may simultaneously transmit k+1 data frames (I-th data frame and k data frames) within T _I,J time.

In step 2, the AP transmits the modified NDPA through a primary channel to initialize the sounding feedback sequence. The modified NDPA is shown in FIG. 2 . As shown in FIG. 2 , the modified NDPA includes one or more STA Info fields including channel index information required for MU-MIMO downlink transmission. After the modified NDPA is transmitted and a short interframe interval (SIFS) time elapses, VHT NDPs are transmitted through each 20 MHz channel bandwidth. The STA corresponding to the first STA Info field of the NDPA transmits VCB frames, that is, VHT compressed beamforming frames, to the AP through each 20 MHz channel bandwidth. The AP transmits a beamforming report poll (BRP) frame necessary to receive VCB frame responses from the intended STAs. At this time, the AP uniquely transmits the NDP and the BRP through the channel bandwidth required for each polled STA. As a result, this method has the effect of reducing overhead information required to obtain channel information.

In step 3, after obtaining channel information from all STAs, the AP transmits data to each STA through a corresponding channel.

In step 4, after each STA finishes receiving data, each STA transmits block ACKs (BAs) in the order in which VCBs are transmitted through the allocated bandwidth.

3 shows an example of performing DL MU-MIMO transmission using an 80 MHz channel bandwidth in the above proposed scheme. It is assumed that one AP has a stream to transmit to three STAs. And, each stream has a different data size and the same MCS. First, the AP determines a transmission band for each stream to be transmitted through a proposed method, for example, an algorithm. In FIG. 3 , the data size to be transmitted to STA3 is the largest, and the data size to be transmitted to STA1 and STA2 is smaller than B _J-1 /B _J of the data size to be transmitted to STA3. Therefore, the AP recognizes that data for STA1 and STA2 can be transmitted through a 40 MHz channel band within a time for transmitting to STA3. Thereafter, the AP transmits (broadcasts) the NDPA through the 20 MHz channel band and the NDP through all the channel bands to obtain channel state information (CSI) from the STAs. STA3 in the first STA Info field of NDPA becomes the first responder. The AP simultaneously polls STA1 and STA2 through another 40 MHz channel bandwidth. After obtaining CSI from each STA, the AP starts DL MU-MIMO transmission through the corresponding channel bandwidth. Here, the AP sends a data frame to STA1 through secondary channels 2 and 3, to STA2 through primary and secondary channels 1, and to STA3 through an 80 MHz channel bandwidth. send them Finally, each STA transmits the BA in the same order as that of the VCB and in the same channel bandwidth.

Meanwhile, the external device includes a content server that provides various types of services. Representatively, a portal server that provides a portal service corresponds to this. In addition, various companies may provide various contents through homepages or the like on the web.

4 is a block diagram illustrating a detailed structure of the wireless LAN device of FIG. 1 .

As shown in FIG. 4 , the wireless LAN device 111 of FIG. 1 according to an embodiment of the present invention can operate as a multi-user multi-input multi-output downlink transmission scheduling device in a local area wireless network (WLAN). Some or all of the interface unit 400 , the control unit 410 , the scheduling unit 420 , and the storage unit 430 are included.

Here, “including some or all” means that some components such as the storage unit 430 are omitted, or some components such as the scheduling unit 420 are integrated into other components such as the control unit 410 . As meanings that can be configured and configured, it will be described as including all in order to help a sufficient understanding of the invention.

The communication interface unit 400 communicates with the plurality of terminals 100 of FIG. 1 . Communication according to the IEEE 802.11ac standard according to an embodiment of the present invention may be performed. In other words, the communication interface unit 400 processes NDP to know the channel state information (CSI) of each terminal 100 before transmitting each spatial stream to each terminal 100 . For example, the communication interface unit 400 may transmit NDPA to each terminal 100 to obtain CSI, initialize a sounding feedback sequence, and the like.

The control unit 410 performs overall control operations of the communication interface unit 400 , the scheduling unit 420 , and the storage unit 430 of FIG. 4 . Representatively, the control unit 410 performs a scheduling operation according to an embodiment of the present invention in conjunction with the scheduling unit 420 . In other words, when a data frame of a specific time is transmitted to a plurality of terminals 100, that is, when performing a multi-user multiple input multiple output downlink operation, the maximum channel bandwidth is allocated to the data frame with the longest transmission time, and , each spatial stream is processed in a manner of allocating data frames to be transmitted to the remaining terminals 100 based on this. Through this, the transmission times of the remaining terminals 100 are matched within the transmission time of the data frame of the maximum length transmitted every time. More precisely, it can be considered to be included within the corresponding maximum transmission time.

The scheduling unit 420 transmits to a plurality of terminals 100 when performing IEEE 802.11ac communication with the terminal 100 of multiple users using an antenna capable of multiple input and multiple output according to an embodiment of the present invention. The data frame is scheduled for transmission, that is, the stream is transmitted by adaptively allocating an antenna and a channel bandwidth based on the size and transmission rate (eg, MCS, etc.) of the data frame according to a preset scheduling program. Here, adaptive means changing according to the environment in which it is placed. Incidentally, it may mean that the state is continuously changed according to time change and the stream is transmitted dynamically. Although this may be slightly different depending on the number of antennas (eg, 4 or 8, etc.) or the number of channel bandwidths for transmitting each spatial stream, it is not significantly different in terms of performing an adaptive operation.

More specifically, the scheduling unit 420 performs the operations described above with reference to FIGS. 2 and 3 . When a spatial stream is transmitted to the terminals 100 in each space, an internal program, that is, a preset algorithm, may be executed under the control of the controller 410 to determine a channel bandwidth required for transmission to each terminal 100 . In addition, the operations of steps 1-1 to 4 described above may be performed. It is preferable that the scheduling unit 420 according to an embodiment of the present invention perform communication according to the IEEE 802.11ac standard. However, in this process, the modified NDPA as shown in FIG. 2 may be transmitted. In this way, it is possible to reduce overhead information.

In addition, the scheduling unit 420 transmits a data stream to each terminal 100 after processing the NDP operation for obtaining CSI. In addition, after each terminal 100 has finished receiving data, it can be checked whether BAs are transmitted in the order in which VCBs are transmitted, for example, through a channel band allocated to each terminal 100 . Accordingly, when the data stream transmission at a specific time is completed, the above operation may be repeated to transmit the data stream at the next time. Of course, in this process, the maximum transmission time of the data frame transmitted to the plurality of terminals 100 at a specific time may be different, and in this way, the scheduling unit 420 is adaptive to spatial streams having different transmission times according to the frame size. It is possible to increase throughput efficiency for DL MU-MIMO by allocating an antenna and a bandwidth.

The storage unit 430 may store and output data or information processed under the control of the control unit 410 . The data stream for transmission to the plurality of terminals 100 in the storage 430 may be temporarily stored and then output under the control of the controller 410 to be transmitted to the plurality of terminals 100 .

In addition to the above, the communication interface unit 400, the control unit 410, the scheduling unit 420, and the storage unit 430 according to an embodiment of the present invention may perform various operations, and other details will be sufficiently described above. So, I would like to substitute those contents.

Meanwhile, as another embodiment of the present invention, the control unit 410 may include a CPU and a memory, and may be formed as a single chip. The CPU includes a control circuit, an arithmetic unit (ALU), a command interpreter and a registry, and the memory may include a RAM. The control circuit performs a control operation, the operation unit performs an operation operation of binary bit information, and the instruction interpretation unit converts a high-level language into a machine language and a machine language into a high-level language, including an interpreter or compiler. , the registry may be involved in software data storage. According to the above configuration, for example, at the beginning of the operation of the wireless LAN device 111 of FIG. 1 , the program stored in the scheduling unit 420 is copied, loaded into a memory, that is, a RAM, and then executed, thereby speeding up data operation processing. can be increased quickly.

5 is a flowchart illustrating a driving process of a wireless LAN device according to an embodiment of the present invention.

Referring to FIG. 5 together with FIG. 1 for convenience of explanation, the wireless LAN device 111 according to an embodiment of the present invention is an OFDM-based multi-user multiple input multiple output downlink transmission scheduling device, and includes a plurality of peripheral terminals (STAs). It communicates with (100) (S500).

In addition, when transmitting a data stream to the plurality of terminals 100 by communication, the wireless LAN device 111 adaptively includes an antenna and a channel bandwidth based on the frame size and transmission rate of the data stream to be transmitted to the plurality of terminals 100 . is selected and transmitted to match the transmission time of each spatial stream of a plurality of terminals 1000 within the maximum transmission time (S510).

Here, adaptive may mean that the selected antenna channel bandwidth is dynamically changed according to time change (eg, t1, t2, ... , t(n-1), tn). Of course, the changed criterion may mean the size of a frame, for example, the length of data stored in a payload part in a data packet, and the transmission rate may include MCS and the like. Of course, in the embodiment of the present invention, since the data transmission rate per second may be the same, an adaptive data transmission operation may be performed only for the size of the data frame. Stream also implies a meaning when data is transmitted in real time or seamlessly.

For example, when three terminals 100 receive a data stream, the maximum channel bandwidth is first allocated to the terminal 100 receiving the stream of the maximum frame size, and then, each according to the size of the data frame of the remaining terminals. of channel bandwidth can be allocated. Accordingly, the terminal 100 to which the maximum channel bandwidth is allocated may be changed, and the maximum transmission time may also be changed. The remaining terminals 100 transmit within the transmission time of the terminal 100 to which the maximum bandwidth is allocated.

In addition to the above, the wireless LAN device 111 according to an embodiment of the present invention can perform various operations as an OFDM-based multi-user multiple input multiple output downlink transmission scheduling device. I want to replace them with

On the other hand, even though it has been described that all components constituting the embodiment of the present invention are combined or operated in combination, the present invention is not necessarily limited to this embodiment. That is, within the scope of the object of the present invention, all the components may operate by selectively combining one or more. In addition, although all the components may be implemented as one independent hardware, some or all of the components are selectively combined to perform some or all of the functions of the combined hardware in one or a plurality of hardware program modules It may be implemented as a computer program having Codes and code segments constituting the computer program can be easily inferred by those skilled in the art of the present invention. Such a computer program is stored in a computer-readable non-transitory computer readable media, read and executed by the computer, thereby implementing an embodiment of the present invention.

Here, the non-transitory readable recording medium refers to a medium that stores data semi-permanently and can be read by a device, not a medium that stores data for a short moment, such as a register, cache, memory, etc. . Specifically, the above-described programs may be provided by being stored in a non-transitory readable recording medium such as a CD, DVD, hard disk, Blu-ray disk, USB, memory card, ROM, and the like.

In the above, preferred embodiments of the present invention have been illustrated and described, but the present invention is not limited to the specific embodiments described above, and it is common in the technical field to which the present invention pertains without departing from the gist of the present invention as claimed in the claims. Various modifications may be made by those having the knowledge of, of course, and these modifications should not be individually understood from the technical spirit or perspective of the present invention.

100: terminal 110: communication network
111: wireless LAN device 400: communication interface unit
410: control unit 420: scheduling unit
430: storage

Claims (12)

A multi-user multiple input multiple output downlink (DL MU-MIMO) scheduling device comprising:
a communication interface unit communicating with a plurality of peripheral terminals; and
When a data stream is transmitted to a plurality of terminals by the communication, an antenna and a channel bandwidth are adaptively selected and transmitted based on a frame size and a transmission rate of a data stream to be transmitted to the plurality of terminals, and each of the plurality of terminals is transmitted. A control unit that matches the transmission time of the spatial stream within the maximum transmission time;
OFDM-based multi-user multi-input multi-output downlink scheduling apparatus including According to claim 1,
The control unit is configured to dynamically change a preset number of antennas and channel bandwidths according to time changes based on a frame size and a transmission rate of the data stream to transmit data streams to the plurality of terminals. Multiple output downlink scheduling device. According to claim 1,
The control unit transmits the data stream by allocating a maximum channel bandwidth to a data stream occupying a maximum transmission time to be transmitted to one of the plurality of terminals when the transmission rates are the same, and then allocating the remaining channel bandwidth to data streams of the remaining terminals Based multi-user, multi-input, multi-output, downlink scheduling device. 4. The method of claim 3,
The control unit, OFDM-based multi-user multi-input multiplexing, processes a null data packet (NDP) for checking channel state information (CIS) for the plurality of terminals before transmitting each spatial stream to the plurality of terminals Output Downlink Scheduling Device. 5. The method of claim 4,
The control unit transmits OFDM-based multi-user multi-input multi-output downlink transmission for each transmitting a beamforming report poll (BRP) frame for receiving a frame response through a channel bandwidth allocated to each of the remaining terminals before transmitting each spatial stream. scheduling device. According to claim 1,
The control unit is an OFDM-based multi-user multiple-input multiple-output downlink transmission scheduling apparatus for processing the data stream according to a communication standard of IEEE 802.11ac. A method of driving a multi-user multiple input multiple output downlink (DL MU-MIMO) scheduling device, the method comprising:
The communication interface unit, the step of communicating with a plurality of peripheral terminals; and
When the control unit transmits the data stream to the plurality of terminals through the communication, the controller adaptively selects and transmits an antenna and a channel bandwidth based on the frame size and transmission rate of the data stream to be transmitted to the plurality of terminals, and transmits each of the plurality of terminals. matching the transmission time of the spatial stream within the maximum transmission time;
A method of driving an OFDM-based multi-user, multiple-input, multiple-output, downlink transmission scheduling apparatus comprising: 8. The method of claim 7,
Transmitting the data stream to the plurality of terminals by dynamically changing a preset number of antennas and channel bandwidth according to time change based on the frame size and transmission rate of the data stream; A driving method of a multiple input multiple output downlink scheduling device. 8. The method of claim 7,
When the transmission rates are the same, allocating a maximum channel bandwidth to a data stream occupying a maximum transmission time to be transmitted to one of the plurality of terminals, and then allocating the remaining channel bandwidth to data streams of the remaining terminals to transmit the data stream; further comprising A method of driving an OFDM-based multi-user multi-input multi-output downlink transmission scheduling device. 10. The method of claim 9,
Before transmitting each spatial stream to the plurality of terminals, processing a null data packet (NDP) for checking channel state information (CIS) for the plurality of terminals; A method of driving an input multiple output downlink scheduling device. 11. The method of claim 10,
The step of processing the NDP,
Method of driving an OFDM-based multi-user multiple input multiple output downlink scheduling apparatus comprising transmitting each BRP frame for receiving a frame response through a channel bandwidth allocated to each of the remaining terminals before transmitting each spatial stream . 8. The method of claim 7,
The communicating step is
A method of driving an OFDM-based multi-user, multiple-input, multiple-output downlink transmission scheduling apparatus that processes the data stream according to the IEEE 802.11ac communication standard.

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