KR102047335B1 - Wireless communication system including communication apparatus and method of communicating data thereof - Google Patents

Abstract

A data transmission method is disclosed. The data transfer method adjusts the data transfer rate when the number of retransmissions of one data transfer unit data reaches a preset number during data transfer at a preset default data transfer rate, and transmits the data transfer unit at the adjusted data transfer rate. If the transmission is successful, the data transmission rate is adjusted to the default data transmission rate; and if the at least one of the retransmission rate and the number of transmission failures calculated during the data transmission satisfies a predetermined threshold condition, the data transmission rate is reduced. do. Accordingly, the data transmission method can efficiently transmit data within limited resources.

Description

Wireless communication system and data communication method including communication device {WIRELESS COMMUNICATION SYSTEM INCLUDING COMMUNICATION APPARATUS AND METHOD OF COMMUNICATING DATA THEREOF}

The present invention relates to a wireless communication system and a data communication method including a communication device, and more particularly, to a wireless communication system and a data communication method including a communication device for communication using a link adaptation scheme.

Recently, with the development of information and communication technology, various wireless communication technologies have been developed. Among them, Wireless Local Area Network (WLAN) uses portable terminals such as smartphones, tablet PCs, laptop computers, portable multimedia players, etc. within a certain distance centered on where access point (AP) is installed. It is a technology that allows you to connect to the Internet wirelessly.

The IEEE, the standardization body, is doing a lot of standardization work on WLAN technology. The use of technical standards is up to IEEE 802.11n, and transmission rates up to 600 Mbps are possible. In addition, the initial radio wave reach was only within 10m, but recently increased to 50-200m. More specifically, IEEE 802.11n is made by adding a frame aggregation technology of a physical layer and a MAC layer with a multiple input and multiple output (MIMO) and 40 MHz channel bandwidth over the existing 802.11 standard.

However, higher bit rates can transmit more data, but provide lower throughput on lost links. In general, lower bit rates have a lower loss probability. Communication systems require data transmission at an efficient and appropriate transmission rate. One such efficient data transmission method is link adaptation. Link adaptation is a process for increasing data throughput using the highest possible rate using a particular modulation and coding scheme at a given link quality.

As a method of link adaptation, there are ARF (AutoRate Fallback) and RBAR (Receiver Based Auto Rate) based on Request-To-Send / Clear-To-Send (RTS / CTS). However, the ARF method is heuristic and has a disadvantage in that it cannot respond quickly to changes in radio channel conditions. The RBAR method has a lot of changes to the IEEE 802.11 standard, and has a disadvantage in that the consumption of radio resources is large. Accordingly, there is a need for a technology capable of efficiently transmitting data and appropriately responding to instantaneous changes in channels.

1: JP Patent Application Publication No. 2010-232819 (2010.10.14.) 2: KR Patent Publication No. 10-2012-0091021 (2012.08.17.)

SUMMARY OF THE INVENTION The present invention has been made in accordance with the above-described needs, and includes link adaptation combining long-term link adaptation reflecting channel tendency and short-term link adaptation corresponding to instantaneous change of channel. It is an object of the present invention to provide a wireless communication system and a data communication method including a communication device applying a scheme.

According to an embodiment for achieving the above object of the present invention, in the data transmission method, when the number of retransmissions of one data transmission unit data reaches a predetermined number of times while performing data transmission at a preset basic data transmission rate, the data transmission rate If the transmission is successful by transmitting the data transmission unit at the adjusted data transmission rate, readjusting the data transmission rate to the basic data transmission rate and at least the retransmission rate and the number of transmission failures calculated during the data transmission. Reducing one of the basic data transmission rates if one meets a predetermined threshold condition.

Meanwhile, in the adjusting of the basic data transmission rate, when the preset recovery condition is satisfied, the basic data transmission rate may be adjusted.

The recovery condition may be at least one of a preset retransmission rate and a preset period.

According to an embodiment of the present invention, a wireless communication device includes a communication unit for communicating with an external node, a storage unit for storing a preset speed adjustment condition, a communication state with the external node, and the speed adjustment condition. And a control unit for adjusting a communication speed with respect to the external node, wherein the control unit has a threshold number of times that the number of retransmissions of one data transmission unit is stored in the storage unit while performing data transmission at a preset default data transmission rate. If the data transmission rate is adjusted, the data transmission unit is transmitted at the adjusted data transmission rate, and if the transmission is successful, the data transmission rate is adjusted to the basic data transmission rate, and the retransmission rate and transmission failure calculated during the data transmission are adjusted. At least one of a number of times a threshold condition stored in the storage unit When satisfied reduces the basic data rate.

The controller may adjust the basic data transmission rate when a preset recovery condition is satisfied.

The recovery condition may be at least one of a preset retransmission rate and a preset period.

According to an embodiment for achieving the above object of the present invention, a communication system includes a plurality of user terminal devices and an AP for communicating with each of the plurality of user terminal devices, and adjusting a communication speed according to each communication state. The AP may adjust the data transmission rate when the number of retransmissions of one data transmission unit reaches a preset number during data transmission at a preset basic data transmission rate for each of the plurality of user terminal devices. If the data transmission unit is transmitted at a data transmission rate and the transmission is successful, the data transmission rate is readjusted to the basic data transmission rate, and at least one of the retransmission rate and the number of transmission failures calculated during the data transmission is set to a preset threshold condition. If satisfied, the base data transmission rate is reduced.

The AP may adjust the basic data transmission rate if a preset recovery condition is met.

The recovery condition may be at least one of a preset retransmission rate and a preset period.

Meanwhile, at least one of the threshold condition and the recovery condition may be separately set according to each terminal device.

As described above, according to various embodiments of the present disclosure, the wireless communication apparatus may efficiently and appropriately transmit data in response to a tendency of a channel and a momentary change of a channel in a predetermined period.

1 is a diagram illustrating a data frame format according to an embodiment of the present invention.
2 to 3 illustrate a link adaptation scheme according to an embodiment of the present invention.
4 is a flowchart illustrating a data transmission method according to an embodiment of the present invention.
5 is a block diagram showing the configuration of a wireless communication device according to an embodiment of the present invention.
6 illustrates a communication system according to an embodiment of the present invention.
7 is a timing diagram illustrating a communication system to which a link adaptation scheme is applied according to an embodiment of the present invention.
8 illustrates a link adaptation scheme in a communication system according to an embodiment of the present invention.
9 is a flowchart of a link adaptation scheme according to an embodiment of the present invention.

Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

1 is a diagram illustrating a data frame format according to an embodiment of the present invention.

Referring to (1) of FIG. 1, a frame format of a MAC Protocol Data Unit (MPDU) is illustrated. A protocol data unit (PDU) refers to information transmitted in a unit between peer entities of a network and may include control information such as an address, data, and the like. In a layer system, a data unit designated by a protocol of a specific layer may mean a data unit composed of data and protocol control information available in a corresponding layer.

The MPDU is a message exchanged between MAC entities in a communication system based on a layered Open Systems Interconnection (OSI) model. In a system, the MPDU may be larger than the MAC Service Data Unit (MSDU). At this time, the MPDU may include a plurality of MSDUs as a result of packet aggregation. In addition, the MPDU in the system may be smaller than the MSDU. At this time, the MSDU may generate a plurality of MPDUs as a result of packet division.

According to an embodiment, the MPDU may include a MAC header, a variable frame body field, and a frame check sequence (FCS) field. The MAC header may include a frame control field, a duration / ID field, an address field, and a sequence control field. The MAC header and FCS field may consist of 28 bytes in total.

The frame control field may consist of 2 bytes and may include a protocol version and information for identifying the type of frame used. The duration / ID field may consist of two bytes and include network allocation vector (NAV) information, contention free period (CFP) information, association ID (AID) information, and the like. Can be. The address fields may consist of six bytes each. The Address 1 field is used for the receiver, the Address 2 field is used for the sender, and the Address 3 field is used for filtering by the receiver. The address 4 field may be used for a data frame of a wireless distribution system (WDS) distributed from one access point (AP) to another access point (AP). Thus, the Address 4 field can optionally be used.

The sequence control field may consist of 2 bytes. The sequence control field can be used for defragmentation and discarding copy frames. The frame body may include transmission data. 802.11 may transmit a frame of payload of up to 2304 bytes. The FCS may consist of 4 bytes. FCS may be referred to as Cyclic Redundancy Check (CRC). The FCS may check the integrity of the received frame.

Referring to Fig. 1 (2), the frame format of the ACK frame is shown. The ACK frame may consist of a MAC header and an FCS field. The MAC header may be composed of a frame control field of 2 bytes, a duration field of 2 bytes, and a receiver address field of 6 bytes. The FCS field may consist of 4 bytes.

The data may be transmitted after a physical layer convergence procedure (PLCP) preamble and a PCLP header are added to the MPDU to generate a PLCP protocol data unit (PPDU).

The above-described MPDU may be one data unit and may be transmitted using link adaptation (LA). The following describes how to apply link adaptation.

2 to 3 are diagrams illustrating a link adaptation scheme according to an embodiment of the present invention.

Referring to FIG. 2, a long-term LA module 11 and a short-term LA module 13 are shown. Long-term LA means LA reflecting the trend of the channel for a certain period. For example, the predetermined period may be set based on the number of thousands to tens of thousands of MPDUs, or may be set in units of time such as tens of milliseconds (ms) or several seconds. Short-term LA may be applied to each MPDU transmission in order to respond to a momentary change of the channel. Alternatively, the short-term LA may be set as several tens of microseconds (us) or hundreds of microseconds (us).

There is no clear guideline for how or when to apply LA. Whether or not the LA estimates the current channel, raises or lowers the rate, and how to determine the LA application period is important. False rate increase or decrease by LA results in lower throughput. According to the 802.11 link type, most of the channel characteristics of WLAN have a characteristic of lowering a transmission success rate when attempting an MCS higher than an appropriate Modulation and Coding Scheme (MCS), and thus lowering a yield. In particular, in the case of an incorrectly determined transmission rate, a failure in MPDU transmission may occur, resulting in a severe yield drop depending on traffic characteristics. MCS means a step of transmission rate defined according to certain criteria. IEEE 802.11n defines a number of designs and their transmission rates according to standards. An example of the maximum transmission rate for each mode is shown in the following table.

MCS
Index
Spatial
Streams Modula-
tion
Type
Coding
Rate Data Rate Mb / s 20 MHz Chnnel 40 MHz Channel 800 ns GI 400 ns GI 800 ns GI 400 ns GI 0 One BPSK 1/2 6.50 7.20 13.50 15.00 One One QPSK 1/2 13.00 14.40 27.00 30.00 2 One QPSK 3/4 19.50 21.70 40.50 45.00 3 One 16-QAM 1/2 26.00 28.90 54.00 60.00 4 One 16-QAM 3/4 39.00 43.30 81.00 90.00 ... 31 4 64-QAM 5/6 260.00 288.90 540.00 600.00

For example, in TCP traffic, when consecutive transmission failures occur, the congestion control mechanism operates to reduce the transmission window size, resulting in a drop in yield even though the channel is in good condition. In addition, since wireless communication requires high performance at low CPU clock and bus clock due to the characteristics of a low power on SoC (Systme On Chip), a short period of LA requires an additional algorithm execution process for LA. Can act as an element

Accordingly, the period in which the LA is applied is implemented separately from the module 11 corresponding to the long-term channel change and the module 13 corresponding to the short-term channel change. The long-term LA module 11 and the short-term LA module 13 may be implemented in hardware or software, respectively. Preferably, the long-term LA module 11 may be implemented in software, and the short-term LA module 13 may be implemented in hardware. The LA module implemented in software is advantageous in terms of resources, because the software requires the computing power of the CPU, and it may be advantageous in terms of resources, and may reflect trends rather than instantaneous channel changes.

The long-term LA module 11 is useful to reflect the trend of the channel but is insufficient to cope with instantaneous changes. Therefore, the short-term LA module 13 that can cope with the instantaneous change of the channel is implemented separately. Since the short-term LA module 13 implemented in hardware performs a hardware-defined operation without any part to be processed by software, the short-term LA module 13 may be processed without using the computational power of the CPU. Therefore, processing delay by software does not occur. For example, if a low-power SoC system needs to process more than 10,000 MPDUs per second, then using software code for short-term LA operations can handle context switching, bus arbitrating, and so on. Delays may occur. Therefore, the short-term LA module 13 implemented in hardware can effectively improve throughput while responding to channel changes and saving resources. The combination of the software-implemented long-term LA module 11 and hardware-implemented short-term LA module 13 can achieve effective performance within limited resources.

3 is a diagram illustrating link adaptation by combining a long-term LA and a short-term LA according to an embodiment of the present invention. As described in FIG. 2, the transmission rate of the MCS and the transmission rate may not be exactly the same, but the present invention will be described with the same concept as the transmission rate. Prior to describing the table illustrated in FIG. 3, the MCS determination method of each of the long-term LA and the short-term LA will be described.

The MCS determination of the long-term LA may use a retransmission rate or a transmission failure count. That is, at least one of a preset retransmission rate or a transmission failure count may be a threshold condition. For example, the first threshold condition may be set as 20% retransmission rate, the second threshold condition is 30% retransmission rate. In this case, when the retransmission rate is 20% for a predetermined period, the long-term LA module 11 lowers the MCS by a predetermined level. During the same period, when the retransmission rate reaches 30%, the MCS is additionally lowered by a predetermined level.

The threshold condition may be set by combining both the retransmission rate and the number of transmission failures. For example, the threshold condition may be set as 10% retransmission rate and 3 times of transmission failures. In this case, the long-term LA module 11 lowers the MCS when both the retransmission rate 10% and the number of transmission failures are satisfied three times. Alternatively, the threshold condition may be set as 10% retransmission rate or 3 times of transmission failures.

In addition, the long-term LA module 11 increases the data transmission rate when a preset recovery condition is reached. The recovery condition may be at least one of a preset retransmission rate or a preset period. For example, the first recovery condition may be set to 25% retransmission rate and the second recovery condition to 15% retransmission rate. In this case, when the retransmission rate reaches 30% or more and the data transmission succeeds continuously and the retransmission rate reaches 25%, the wireless communication device raises the MCS by a predetermined level. When the predetermined period ends and a new period begins, the wireless communication device may recover the MCS of the initially set basic data transmission rate and perform data transmission of the next period.

The MCS determination of the short-term LA may use the number of retransmissions of the MPDU. For example, the level 1 of the short-term LA may be set as 3 times of retransmissions, and the level 2 of the short-term LA may be set as 5 times of retransmissions. Similar to the MCS determination method of the long-term LA, the MCS of the short-term LA is set to a preset level when a corresponding level condition is satisfied. However, when the short-term LA transmission of one MPDU is successful, the short-term LA recovers the original MCS and transmits the next MPDU. For example, when the number of retransmissions of the MPDU is three, the short-term LA module 13 attempts to transmit again by lowering the level than the basic MCS. If the transmission is successful, the short-term LA module 13 recovers to the basic MCS and attempts to transmit the next MPDU.

3 shows a table combining the long-term LA and the short-term LA. Currently, the long-term LA module 11 is set to MCS 12. When the number of retransmissions is zero, the short-term LA module 13 sets the short-term LA level 1 (MCS 12), and the wireless communication device transmits an MPDU. When the number of retransmissions is three times while transmitting the second MPDU, the short-term LA module 13 sets the short-term LA level 2 (MCS 11), and the wireless communication device transmits the second MPDU. If the second MPDU transmission is successful, the short-term LA module 13 restores the transmission rate to MCS 12, which is the default transmission rate set in the long-term LA module 11. When the number of retransmissions is three times while transmitting the third MPDU, the short-term LA module 13 sets the short-term LA level 2 (MCS 11). If the third MPDU transmission continues to fail and the number of retransmissions is five, the short-term LA module 13 sets the short-term LA level 3 (MCS 10). If the third MPDU transmission is successful, the short-term LA module 13 restores the transmission rate to MCS 12, which is the default transmission rate.

The link adaptation for transmitting data by combining the above-mentioned long-term LA and short-term LA will be described in detail with reference to a flowchart.

4 is a flowchart illustrating a data transmission method according to an embodiment of the present invention.

Referring to FIG. 4, the wireless communication device transmits data at a preset data transmission rate (S410). The preset data transmission rate may be indicated by a preset MCS index. The transmitted data may be in MPDU units. The wireless communication device determines whether a data transmission error has occurred (S420). The data transmission error may be determined using an ACK frame transmitted from the receiver. For example, when the wireless communication device does not receive any ACK frame from the receiver or receives the ACK frame but is not normal data, the wireless communication device determines that the transmission error. If a data transmission error does not occur, the wireless communication device maintains a basic data transmission speed (S480).

If a data transmission error occurs, the wireless communication device attempts to retransmit at the currently set data transmission rate (S430). The wireless communication device determines whether data transmission is successful (S440). If the data transmission fails, the short-term LA module 13 determines whether the number of retransmissions is a preset number (S450). If the number of retransmissions is not the preset number, the short-term LA module 13 maintains the current setting data transmission rate. If the number of retransmissions is a preset number, the short-term LA module 13 adjusts the preset data transmission rate corresponding to the preset number of retransmissions (S460). The wireless communication device attempts retransmission at the adjusted data transmission rate (S430).

If the data transmission is successful, the long-term LA module 11 determines whether at least one of the retransmission rate or the number of transmission failures is a predetermined threshold condition (S470). If not, the long-term LA module 11 maintains the currently set basic data transmission rate (S480). If the threshold condition is satisfied, the long-term LA module 11 reduces the basic data transmission speed (S490). 4 is described based on one transmission period. When one preset transmission period ends, the long-term LA module 11 recovers to the preset basic data transmission rate, and the wireless communication device starts data transmission again.

Hereinafter, a wireless communication device will be described.

5 is a block diagram illustrating a configuration of a wireless communication device according to an embodiment of the present invention.

Referring to FIG. 5, the wireless communication device 100 includes a communication unit 110, a storage unit 120, and a control unit 130. The wireless communication device 100 shown in FIG. 5 may perform a link adaptation procedure combining the above-mentioned long-term LA and short-term LA.

The communication unit 110 performs communication with an external node. That is, the controller 130 transmits wireless data generated by the controller 130 and receives wireless data transmitted by another wireless communication device. The communicator 110 may transmit or receive a radio signal in a broadcast or unicast manner.

The storage unit 120 stores a preset speed adjustment condition. In addition, the storage 120 may store a control program for controlling the wireless communication device 100 or the controller 130. The storage unit 120 may include, for example, a memory card (eg, an SD card or a memory stick) that is removable / mounted to the ROM, the RAM, or the wireless communication device 100. In addition, the storage 120 may include a nonvolatile memory, a volatile memory, a hard disk drive (HDD), or a solid state drive (SDD).

The controller 130 adjusts the communication speed for the external node according to the communication state and the speed adjustment condition with the external node. The controller 130 includes a long-term LA module and a short-term LA module. The long-term LA module and the short-term LA module may be implemented in hardware or software. In one embodiment, the long-term LA module is implemented in software, the short-turn LA module is preferably implemented in hardware.

The controller 130 performs data transmission at a preset default data transmission rate, and adjusts the data transmission rate when the number of retransmissions of one data transmission unit becomes a threshold condition. The controller 130 transmits the data transmission unit at the adjusted data transmission rate. If the transmission is successful, the controller 130 readjusts the data transmission rate to the basic data transmission rate.

In addition, the controller 130 decreases the basic data transmission speed when at least one of the retransmission rate and the transmission failure count calculated during data transmission meets a threshold condition. The wireless communication apparatus 100 may set a retransmission rate or a period in advance and set the recovery condition, and the controller 130 may adjust the basic data transmission rate when the recovery condition is satisfied.

Up to now, it has been assumed that one wireless communication device 100 transmits data to one terminal device. The wireless communication device 100 may transmit data to a plurality of terminal devices. In this case, the wireless communication device 100 may individually set and transmit a transmission condition for each terminal device. Hereinafter, an embodiment of transmitting data to a plurality of terminal devices will be described.

6 is a diagram illustrating a communication system according to an embodiment of the present invention.

Referring to FIG. 6, one AP 100 and a plurality of terminal devices 200a, 200b, and 200c are illustrated.

LA for data transmission from the AP 100 to the plurality of terminal devices 200a, 200b, and 200c may be performed for each terminal device. In IEEE 802.11, the basic unit of service providing object is an association ID (AID). That is, the plurality of terminal devices 200a, 200b, and 200c are individually provided with one AID in a basic service set (BSS) and receive a data service from the AP 100. Each terminal device 200a, 200b, or 200c physically exists at a different location in the AP 100 and thus has a different channel response for each wireless channel or terminal device. In particular, the quality of a received signal may vary due to a path loss or an obstacle due to a distance difference. Therefore, when the LA is applied, the LA parameters are separately managed based on the AID so that a data rate suitable for the channel environment of each terminal device 200a, 200b, or 200c can be selected.

In the AP 100, each terminal device 200a, 200b, 200c has a separate ID. Accordingly, data to be transmitted to each terminal device 200a, 200b, or 200c may be classified using AID information of a duration / ID field of the MPDU frame format described with reference to FIG. 1. In addition, the AP 100 performs retransmission rate, transmission failure count, retransmission count, MCS, etc. for each AID corresponding to each terminal device 200a, 200b, 200c to perform LA for each terminal device 200a, 200b, 200c. Can manage.

A method of transmitting data to a plurality of terminal devices 200a, 200b, and 200c by using a link adaptation method combining a long-term LA and a short-term LA in one AP 100 will be described below.

7 is a timing diagram illustrating a communication system to which a link adaptation scheme is applied according to an embodiment of the present invention.

Referring to FIG. 7, one AP 100 transmits data to terminal devices 1,2 and 3 (200a, 200b, 200c), respectively. First, the AP 100 transmits data to the terminal device 1 200a (S705). At this time, the AP 100 transmits data at a transmission rate set as a default for the terminal device 1 200a. Terminal device 1 (200a) receives the data, and transmits the ACK signal to the AP (100) (S710). The AP 100 determines that data transmission is normally performed when the ACK signal received from the terminal device 1 200a is normal.

The AP 100 transmits data to the terminal device 2 200b (S715). If the AP 100 does not receive an ACK signal from the terminal device 2 200b or receives an incorrect ACK, the AP 100 determines that data transmission has failed. Therefore, the AP 100 retransmits the same data (S720), and if it is determined that the data transmission is successful, retransmits it again (S725). The threshold condition for the terminal device 2 200b set in the AP 100 is three times of retransmissions. Since the AP 100 meets the threshold condition, the AP 100 reduces the data transmission rate and transmits data again (S730). At this time, when the AP 100 receives a normal ACK signal from the terminal device 2 200b (S735), it determines that data transmission is normally performed. When transmitting the next data transmission unit, the AP 100 attempts to transmit data by recovering to the default data transmission rate set for the terminal device 2 200b.

The AP 100 transmits data to the terminal device 3 200c (S740). The first threshold condition for the terminal device 3 200c configured in the AP 100 is three times of retransmissions, and the second threshold condition is five times of retransmissions. If the AP 100 does not receive an ACK signal from the terminal device 3 300c or receives an incorrect ACK, the AP 100 determines that data transmission has failed. Therefore, the AP 100 attempts to transmit data to the terminal device 3 (200c) a plurality of times (S740, S745, S750). Since the first threshold condition set for the terminal device 3 (200c) is satisfied, the AP 100 reduces the data transmission rate and transmits data (S755), until the normal ACK signal is received from the terminal device 3 (200c). Data transmission is attempted again a plurality of times (S760). Since the second threshold condition set for the terminal device 3 200c is satisfied, the AP 100 again decreases the data transmission rate and transmits data (S765). When the AP 100 receives the normal ACK signal from the terminal device 3 (200c) (S770), it determines that the data transmission is normally performed.

8 illustrates a link adaptation scheme in a communication system according to an embodiment of the present invention.

FIG. 8 is a table showing a combination of long-term LA and short-term LA for a plurality of terminal devices. AID means a separate terminal device. Since the combination of the basic long-term LA and the short-term LA and the link adaptation method are the same as described with reference to FIG.

However, in FIG. 8, the MCS corresponding to the retransmission rate, the transmission failure count, the retransmission rate, and the transmission failure count, which are parameters for determining the basic MCS and the MCS in the long-term LA, may be individually set for each terminal device. In addition, the MCS corresponding to the number of retransmissions and the number of retransmissions, which are parameters for determining the MCS in the short-term LA, may also be individually set for each terminal device. The AP may store parameters for AID and link adaptation of each terminal device in a storage unit.

The AP can perform efficient data transmission within a limited resource for each terminal device by appropriately combining the long-term LA and the short-term LA. Hereinafter, link adaptation will be described by dividing the long-term LA and the short-term LA.

9 is a flowchart of a link adaptation scheme according to an embodiment of the present invention.

Referring to FIG. 9, the wireless communication device determines whether a long-term LA application period is performed in a long-term LA step (S910). In some cases, the wireless communication device always performs the long-term LA without determining whether or not the application cycle is performed, and may determine whether only one cycle is terminated.

If the wireless communication device determines that the long-term LA application period is determined, the wireless communication device determines the MCS based on at least one of a retransmission rate and a transmission failure count (S920). If it is determined that the wireless communication device does not have a long-term LA application period, the wireless communication device applies the MCS determined in the previous long-term LA (S930). When the wireless communication apparatus transmits MPDUs to the plurality of terminal apparatuses, the wireless communication apparatus may individually set parameters according to each terminal apparatus. In addition, the MCS may be adjusted when a predetermined recovery condition is met.

The wireless communication device determines whether the number of retransmissions is preset in the short-term LA step (S940). When transmitting MPDUs to a plurality of terminal devices, the parameters may be individually set according to each terminal device.

If it is determined that the number of retransmissions is not a predetermined number, the MPDU transmission is attempted to the currently set MCS (S960). If it is determined that the preset number of retransmissions, the wireless communication apparatus changes to the set MCS corresponding to the determined number of retransmissions (S950). If the wireless communication device changes the MCS, the wireless communication device attempts to transmit the MPDU to the changed MCS (S960). If the MPDU transmission is successful, the wireless communication device changes to the default MCS and attempts to transmit the next MPDU.

If the transmission fails, the wireless communication device determines again whether the number of retransmissions is a preset number of retransmissions (S970). As such, the wireless communication device may obtain the optimized data communication throughput by performing link adaptation by combining the long-term and the short-term.

The data transmission method according to the above-described various embodiments may be implemented as a program and provided to a wireless communication device.

For example, if data retransmission of one data transmission unit data reaches a preset number during data transmission at a preset default data transmission rate, the data transmission rate is adjusted and the data transmission unit is transmitted at the adjusted data transmission rate. Adjusting the data transmission rate to the default data transmission rate if the transmission is successful; and reducing the basic data transmission rate if at least one of the retransmission rate and the number of transmission failures calculated during the data transmission meets a preset threshold condition. A non-transitory computer readable medium in which a program is stored may be provided.

The non-transitory readable medium refers to a medium that stores data semi-permanently and is readable by a device, not a medium storing data for a short time such as a register, a cache, a memory, and the like. Specifically, the various applications or programs described above may be stored and provided in a non-transitory readable medium such as a CD, a DVD, a hard disk, a Blu-ray disk, a USB, a memory card, a ROM, or the like. In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the above-described specific embodiment, the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

100: wireless communication device 110: communication unit
120: storage unit 130: control unit
200a, 200b, 200c: terminal device

Claims (10)

Setting a base rate of data transmission based on a channel environment during a first period of long-term;
If the number of retransmissions of one data transmission unit data becomes a predetermined number of times during the second period of the short-term while performing data transmission at the set basic data transmission rate, the data transmission rate is adjusted and adjusted. Resizing the data transmission rate during the second period of the short-term to the basic data transmission rate if the transmission is successful by transmitting the one data transmission unit at a data transmission rate; And
Reducing the basic data transmission rate during the first period of the long-term if at least one of the retransmission rate and the number of transmission failures calculated during the data transmission satisfies a preset threshold condition; and,
The first period of the long-term is longer than the second period of the short-term. The method of claim 1,
And adjusting the basic data transmission rate when a preset recovery condition is met. The method of claim 2,
The recovery condition is,
And at least one of a preset retransmission rate and a preset period. A communication unit for communicating with an external node;
A storage unit in which preset speed adjustment conditions are stored; And
And a controller configured to adjust a communication speed for the external node according to a communication state with the external node and the speed adjustment condition.
The control unit,
Set a basic data rate based on the channel environment during the first period of the long-term,
If the number of retransmissions of one data transmission unit during the data transmission at the set basic data transmission rate becomes the threshold number stored in the storage unit during the second period of the short-term, the data transmission rate is adjusted. And, if the transmission is successful by transmitting the one data transmission unit at the adjusted data transmission rate, readjust the data transmission rate during the second period of the short-term to the basic data transmission rate,
If the at least one of the retransmission rate and the number of transmission failures calculated during the data transmission satisfies the threshold condition stored in the storage unit, decreases the basic data transmission rate during the first period of the long-term;
And a first period of the long-term is longer than a second period of the short-term. The method of claim 4, wherein
The control unit,
And adjusting the basic data transmission rate when a preset recovery condition is met. The method of claim 5,
The recovery condition is,
And at least one of a preset retransmission rate and a preset period. In a communication system,
A plurality of user terminal devices; And
An AP for communicating with each of the plurality of user terminal devices and adjusting a communication speed according to each communication state;
The AP,
One of setting a basic data transmission rate for each of the plurality of user terminal devices based on a channel environment during a first period of a long-term, and performing data transmission at the set basic data transmission rate If the number of retransmissions of the data transmission unit of the predetermined number of times during the second period of the short-term is adjusted, the data transmission rate is adjusted, and the one data transmission unit is transmitted at the adjusted data transmission rate. If successful, readjusts the data transfer rate during the second period of the short-term to the base data transfer rate,
If the at least one of the retransmission rate and the number of transmission failures calculated during the data transmission satisfies a predetermined threshold condition, the basic data transmission rate during the first period of the long-term is reduced.
And the first period of the long-term is longer than the second period of the short-term. The method of claim 7, wherein
The AP,
And adjusting the basic data transmission rate when a preset recovery condition is met. The method of claim 8,
The recovery condition is,
And at least one of a preset retransmission rate and a preset period. The method of claim 9,
And at least one of the threshold condition and the recovery condition is set separately according to each terminal device.

Images