Wireless communication method for data simultaneous communication and wireless communication terminal using the same

Abstract

To provide a wireless communication terminal and wireless communication method for data simultaneous communication, and more particularly, a wireless communication terminal and wireless communication method for suppressing interference between terminals and ensuring fairness when performing data simultaneous communication for spatial reuse of a communication system.SOLUTION: A wireless communication terminal includes a transceiver and a processor. The wireless communication terminal receives a wireless signal through the transceiver. The processor is configured to: extract length information from the wireless signal, the length information representing duration of the wireless signal; extract BSS (Basic Service Set) identifier information of the wireless signal; on the basis of the extracted BSS identifier information, determine whether or not the wireless signal is an overlapping BSS wireless signal; and, when it is determined that the wireless signal is an overlapping BSS wireless signal, adjust a TXOP (Transmission Opportunity) of the wireless communication terminal on the basis of the extracted length information.SELECTED DRAWING: Figure 22

Description

[Technical Field]

[0001] The present invention relates to a wireless communication method for simultaneous data communication and a wireless communication terminal using the same, and more particularly to a wireless communication method for suppressing interference between terminals and ensuring fairness when performing simultaneous data communication for spatial reuse of a communication system and a wireless communication terminal using the same. [Background technology]

[0002] Recently, as the popularity of mobile devices has increased, wireless LAN technology, which provides high-speed wireless Internet services to these devices, has been gaining attention. Wireless LAN technology is a technology that uses short-range wireless communication technology to wirelessly connect mobile devices such as smartphones, smart pads, laptop computers, portable multimedia players, and embedded devices to the Internet at home, in businesses, or in specific service areas.

[0003] Since supporting early wireless LAN technology using the 2.4 GHz frequency band, IEEE (Institute of Electrical and Electronics Engineers) 802.11 has since implemented or is developing various other technology standards. IEEE 802.11b supports a maximum communication speed of 11 Mbps using the 2.4 GHz frequency band. IEEE 802.11a, commercialized after IEEE 802.11b, uses the 5 GHz frequency band instead of the 2.4 GHz band, reducing the impact of interference compared to the much more congested 2.4 GHz frequency band, and uses OFDM technology to increase communication speeds to a maximum of 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication distance than IEEE 802.11b. IEEE 802.11g has attracted considerable attention because it uses the 2.4GHz band like IEEE 802.11b to achieve a maximum communication speed of 54Mbps and is backward compatible, but it also has an advantage over IEEE 802.11a in terms of communication distance.

[0004] IEEE 802.11n is a technical standard established to overcome the communication speed limitations that have been identified as a weakness of wireless LANs. IEEE 802.11n aims to increase network speed and reliability and extend the operating distance of wireless networks. More specifically, IEEE 802.11n supports high throughput (HT) of up to 540 Mbps. It also relies on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas on both the transmitter and receiver sides to minimize transmission errors and optimize data speed. This standard also uses a coding method that transmits multiple duplicate copies to increase data reliability.

[0005] As WLAN usage continues to grow and applications become more diverse, a need has arisen for new WLAN systems that support data rates higher than those supported by IEEE 802.11n (Very High Throughput, VHT). IEEE 802.11ac supports wide bandwidth (80MHz-160MHz) in the 5GHz frequency band. While the IEEE 802.11ac standard was defined only for the 5GHz band, initial 802.11ac chipsets also support operation in the 2.4GHz band for backward compatibility with existing 2.4GHz products. Theoretically, this standard enables multi-station WLAN speeds of at least 1Gbps and maximum single-link speeds of at least 500Mbps. This is achieved by expanding the air interface concepts adopted in 801.11n, including wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and denser modulation (up to 256QAM). Additionally, there is IEEE 802.11ad, a method of transmitting data using the 60 GHz band instead of the conventional 2.4 GHz / 5 GHz. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide speeds of up to 7 Gbps, making it suitable for streaming large amounts of data and high-bitrate video, such as uncompressed HD video. However, the 60 GHz frequency band has the disadvantage of being difficult to pass through obstacles and can only be used between devices in close proximity.

[0006] Meanwhile, discussions are currently underway to provide high-efficiency and high-performance wireless LAN communication technology in high-density environments as the next-generation wireless LAN standard after 801.11ac and 802.11ad. In other words, next-generation wireless LAN environments should provide high-frequency-efficient communication both indoors and outdoors in the presence of high-density stations and access points (APs), and various technologies are required to achieve this. Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, an object of the present invention is to provide highly efficient and high performance wireless LAN communication in a high density environment.

[0008] In particular, the present invention has an object to provide a method for effectively transmitting data in an overlapped BSS (Basic Service Set) environment.

[0009] Another object of the present invention is to increase data transmission opportunities and transmission rates by providing an efficient spatial reuse method in an overlapped BSS environment.

[0010] Another object of the present invention is to solve the inequality problem of legacy terminals that may occur when an adjusted CCA threshold is used for channel access.

[0011] Another object of the present invention is to minimize interference problems between terminals in spatial reuse intervals. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides the following wireless communication method and wireless communication terminal.

[0013] First, the present invention provides a wireless communication method for a terminal, including the steps of receiving a wireless signal of a specific channel, measuring the signal strength of the received wireless signal, and determining whether the specific channel is occupied based on the measured signal strength and BSS identifier information of the wireless signal.

[0014] In this case, the determining step is performed based on a CCA (Clear Channel Assessment) for the specific channel, and the CCA threshold value used for the CCA is set to different levels depending on whether the BSS identifier information of the wireless signal is the same as the BSS identifier information of the terminal.

[0015] In addition, if the BSS identifier information of the wireless signal is the same as the BSS identifier information of the terminal, a first CCA threshold is used for the CCA, and if the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal, a second CCA threshold having a higher level than the first CCA threshold is used for the CCA.

[0016] The method further includes a step of acquiring at least one of legacy WLAN information and non-legacy WLAN information using preamble information of the received wireless signal, and the determining step determines whether the specific channel is occupied based on BSS identifier information of the wireless signal if the non-legacy WLAN information is acquired from the wireless signal.

[0017] Next, the present invention provides a wireless communication method for a terminal, including the steps of receiving a wireless signal of a specific channel, measuring a signal strength of the received wireless signal, acquiring at least one of legacy WLAN information and non-legacy WLAN information using preamble information of the received wireless signal, and, if the measured signal strength is between a first CCA threshold and a second CCA threshold and non-legacy WLAN information is acquired from the wireless signal, determining whether the specific channel is occupied based on BSS identifier information of the wireless signal.

[0018] In this case, the BSS identifier information indicates abbreviated information of the BSS identifier for the radio signal.

[0019] According to an embodiment of the present invention, the determining step determines whether the specific channel is occupied based on a result of comparing BSS identifier information of the wireless signal with BSS identifier information of the terminal.

[0020] In this case, the determining step determines that the specific channel is in an idle state if the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal.

[0021] Furthermore, the determining step determines that the specific channel is in an occupied state (busy) if the BSS identifier information of the wireless signal is the same as the BSS identifier information of the terminal.

[0022] According to one embodiment of the present invention, the wireless signal includes a first preamble for legacy terminals and a second preamble for non-legacy terminals, and BSS identifier information of the wireless signal is extracted from the second preamble of the wireless signal.

[0023] According to another embodiment of the present invention, the wireless signal includes a first preamble for a legacy terminal and a second preamble for a non-legacy terminal, and the first preamble is configured to include at least a first subcarrier set for the legacy terminal, but if the first preamble is configured to additionally include a second subcarrier set different from the first subcarrier set, the non-legacy WLAN information is acquired from the second subcarrier set.

[0024] At this time, BSS identifier information of the received wireless signal is extracted from information of the second subcarrier set of the first preamble.

[0025] According to another embodiment of the present invention, the wireless signal includes a first preamble for a legacy terminal and a second preamble for a non-legacy terminal, and whether the wireless signal includes the non-legacy WLAN information is determined based on a preset bit field of the first preamble.

[0026] According to one embodiment, the wireless signal includes a first preamble for legacy terminals and a second preamble for non-legacy terminals, and BSS identifier information of the wireless signal is extracted from a preset bit field of the first preamble.

[0027] In this case, the preset bit of the preset bit field indicates whether the wireless signal includes non-legacy WLAN information, and if the preset bit indicates that the wireless signal includes non-legacy WLAN information, BSS identifier information of the wireless signal is extracted from the preset bit field.

[0028] According to another embodiment, the first preamble is configured to include at least a first subcarrier set for the legacy terminal, and if the first preamble is configured to additionally include a second subcarrier set different from the first subcarrier set, BSS identifier information of the wireless signal is extracted from the preset bit field.

[0029] Next, the present invention provides a wireless communication method for a terminal, comprising the steps of receiving a wireless signal of a specific channel, extracting BSS identifier information of the received wireless signal, and if the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal, extracting length information from the wireless signal, the length information indicating information regarding a transmission completion time of the wireless signal, and adjusting a data transmission period of the terminal based on the extracted length information.

[0030] According to one embodiment, the length information indicates information of a duration field of the radio signal frame.

[0031] According to another embodiment, the length information indicates a Transmission Opportunity (TXOP) of an external terminal transmitting the wireless signal.

[0032] In this case, the length information is obtained from at least one of a legacy preamble, a non-legacy preamble, and a MAC header of the wireless signal.

[0033] According to an embodiment of the present invention, the data transmission period is adjusted to end before the transmission of the radio signal according to the extracted length information is completed.

[0034] More specifically, the data transmission period is adjusted to end at least the sum of a Short Inter Frame Space (SIFS) time and a time required for transmitting a response message before the completion of the transmission of the radio signal.

[0035] Also, the data transmission period indicates the TXOP of the terminal.

[0036] According to a further embodiment of the present invention, the method further includes the steps of measuring the signal strength of the wireless signal and determining whether the specific channel is occupied based on the measured signal strength and the extracted BSS identifier information, and the data transmission period is adjusted when the specific channel is determined to be idle and the terminal approaches the specific channel.

[0037] In addition, the determining step is performed based on the CCA for the specific channel, and the CCA threshold value used for the CCA is set to different levels depending on whether the BSS identifier information of the wireless signal is the same as the BSS identifier information of the terminal.

[0038] In this case, if the BSS identifier information of the wireless signal is the same as the BSS identifier information of the terminal, a first CCA threshold is used for the CCA, and if the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal, a second CCA threshold higher than the first CCA threshold is used for the CCA.

[0039] Next, the present invention provides a wireless communication method for a terminal, including the steps of receiving a wireless signal of a specific channel, and if the wireless signal has BSS identifier information different from that of the terminal, performing CCA based on a second CCA threshold higher than a first CCA threshold for a legacy terminal, and if the channel is determined to be in an idle state as a result of performing the CCA, performing a backoff procedure, if the backoff procedure is interrupted before a backoff counter of the backoff procedure expires, adjusting a backoff counter assigned to the terminal, and if the channel again becomes idle, resuming the backoff procedure using the adjusted backoff counter.

[0040] At this time, the backoff counter allocated to the terminal is adjusted when the received signal strength of the radio signal undergoing the backoff procedure is between the first CCA threshold and the second CCA threshold.

[0041] According to one embodiment, the adjusting step restores the backoff counter to the value it had before the backoff procedure.

[0042] According to another embodiment, the adjusting step comprises allocating a new back-off counter for the terminal.

[0043] Next, the present invention provides a wireless communication method for a terminal, including the steps of: allocating a first backoff counter and a second backoff counter for a backoff procedure of the terminal; receiving a wireless signal having BSS identifier information different from that of the terminal; and performing a backoff procedure based on a received signal strength of the wireless signal, the backoff procedure including expiring the first backoff counter if the received signal strength of the wireless signal is lower than a first CCA threshold for a legacy terminal; expiring the second backoff counter if the received signal strength of the wireless signal is higher than the first CCA threshold and lower than a second CCA threshold; and transmitting data if at least one of the first backoff counter and the second backoff counter expires.

[0044] According to an embodiment of the present invention, the first backoff counter and the second backoff counter are assigned different random number ranges.

[0045] Next, the present invention provides a wireless communication method for a terminal, including the steps of receiving a request message (another BSS request message) having BSS identifier information different from that of the terminal, receiving a response message (another BSS response message) corresponding to the other BSS request message, and determining whether to allow channel access for the terminal based on a received signal strength of the other BSS request message and a received signal strength of the other BSS response message.

[0046] According to an embodiment of the present invention, if the received signal strength of the other BSS response message is lower than the first CCA threshold and the received signal strength of the other BSS request message is lower than the second CCA threshold, the channel access of the terminal is allowed, but the second CCA threshold is set to a level higher than the first CCA threshold.

[0047] According to a further embodiment of the present invention, the method further includes the steps of: transmitting a request message (same BSS request message) indicating that data transmission for the terminal is possible to the receiving terminal when it is determined that the terminal is approaching the channel; and transmitting data to the receiving terminal when a same BSS response message corresponding to the same BSS request message is received from the receiving terminal.

[0048] At this time, if a same BSS response message corresponding to the same BSS request message is not received from the receiving terminal, the channel access of the terminal is postponed.

[0049] According to one embodiment, the request message is a Request-to-Send (RTS) message and the response message is a Clear-to-Send (CTS) message.

[0050] According to another embodiment, the request message is a Null Data Packet (NDP) and the response message is an ACK.

[0051] In another embodiment, the request message is a MAC Protocol Data Unit (MPDU) and the response message is an ACK.

[0052] Next, the present invention provides a wireless communication method for a terminal, including the steps of receiving a request message (another BSS request message) having BSS identifier information different from that of the terminal, receiving a response message (another BSS response message) corresponding to the other BSS request message, receiving a request message (an identical BSS request message) from a transmitting terminal having the same BSS identifier information as that of the terminal and addressing the terminal as a recipient, and determining whether to transmit an identical BSS response message corresponding to the identical BSS request message based on a received signal strength of the other BSS request message and a received signal strength of the other BSS response message.

[0053] In this case, the same BSS response message indicates that the transmitting terminal can receive data.

[0054] According to an embodiment of the present invention, if the received signal strength of the other BSS response message is lower than the second CCA threshold and the received signal strength of the other BSS request message is lower than the first CCA threshold, the same BSS response message is transmitted to the transmitting terminal, but the second CCA threshold is set to a level higher than the first CCA threshold.

[0055] According to one embodiment, the request message is an RTS message and the response message is a CTS message.

[0056] According to another embodiment, the request message is an NDP and the response message is an ACK.

[0057] In another embodiment, the request message is an MDPU and the response message is an ACK.

[0058] Next, the present invention provides a wireless communication terminal including a transceiver unit for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal, wherein the processor measures the signal strength of a wireless signal of a specific channel received via the transceiver unit, and determines whether the specific channel is occupied based on the measured signal strength and BSS identifier information of the wireless signal.

[0059] In this case, the processor acquires at least one of legacy WLAN information and non-legacy WLAN information using preamble information of the received wireless signal, and if the non-legacy WLAN information is acquired from the wireless signal, determines whether the specific channel is occupied based on BSS identifier information of the wireless signal.

[0060] In addition, the processor makes the determination based on the CCA for the specific channel, and the CCA threshold value used for the CCA is set to different levels depending on whether the BSS identifier information of the wireless signal is the same as the BSS identifier information of the terminal.

[0061] Next, the present invention provides a wireless communication terminal including a transceiver unit for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal, wherein the processor measures signal strength of a wireless signal of a specific channel received through the transceiver unit, acquires at least one of legacy WLAN information and non-legacy WLAN information using preamble information of the received wireless signal, and, if the measured signal strength is between a first CCA threshold and a second CCA threshold and non-legacy WLAN information is acquired from the wireless signal, determines whether the specific channel is occupied based on BSS identifier information of the wireless signal.

[0062] Next, the present invention provides a wireless communication terminal including a transceiver unit for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal, wherein the terminal receives a wireless signal of a specific channel via the transceiver unit, the processor extracts BSS identifier information of the received wireless signal, and if the BSS identifier information of the wireless signal differs from the BSS identifier information of the terminal, extracts length information from the wireless signal, the length information indicating information about a time point at which transmission of the wireless signal is completed, and the wireless communication terminal adjusts a data transmission period of the terminal based on the extracted length information.

[0063] Next, the present invention provides a wireless communication terminal including a transceiver unit for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal, wherein the terminal receives a wireless signal of a specific channel through the transceiver unit, and when the wireless signal has BSS identifier information different from that of the terminal, the processor performs CCA based on a second CCA threshold higher than a first CCA threshold for legacy terminals, and when the channel is determined to be in an idle state as a result of the CCA, performs a backoff procedure, and when the backoff procedure is interrupted before a backoff counter of the backoff procedure expires, adjusts a backoff counter assigned to the terminal, and when the channel again becomes idle, resumes the backoff procedure using the adjusted backoff counter.

[0064] Next, the present invention provides a wireless communication terminal including a transceiver unit for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal, wherein the terminal receives a wireless signal having BSS identifier information different from that of the terminal via the transceiver unit, the processor is assigned a first backoff counter and a second backoff counter for a backoff procedure of the terminal, and performs a backoff procedure based on a received signal strength of the wireless signal, the backoff procedure depleting the first backoff counter if the received signal strength of the wireless signal is lower than a first CCA threshold for a legacy terminal, depleting the second backoff counter if the received signal strength of the wireless signal is higher than the first CCA threshold and lower than a second CCA threshold, and the wireless terminal transmits data when at least one of the first backoff counter and the second backoff counter expires.

[0065] Next, the present invention provides a wireless communication terminal including a transceiver unit for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal, wherein the terminal receives a request message (another BSS request message) having another BSS identifier information different from that of the terminal via the transceiver unit, receives a response message (another BSS response message) corresponding to the other BSS request message, and the processor determines whether to allow channel access for the terminal based on the received signal strength of the other BSS request message and the received signal strength of the other BSS response message.

[0066] Next, the present invention provides a wireless communication terminal including a transceiver unit for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal, wherein the terminal receives a request message (another BSS request message) having another BSS identifier information different from that of the terminal, receives a response message (another BSS response message) corresponding to the other BSS request message, receives a request message (same BSS request message) having the same BSS identifier information as the terminal and addressed to the terminal as a recipient from a transmitting terminal, and the processor determines whether to transmit an same BSS response message corresponding to the same BSS request message based on a received signal strength of the other BSS request message and a received signal strength of the other BSS response message. [Effects of the Invention]

[0067] According to an embodiment of the present invention, it is possible to efficiently determine whether wireless signals received in a superimposed BSS environment are the same WLAN signal, and based on this, it is possible to determine whether or not to adaptively utilize the corresponding channel.

[0068] According to another embodiment of the present invention, if the received wireless signal is a legacy WLAN signal from which BSS identifier information is not extracted, the channel occupancy is determined collectively based on the received signal strength of the corresponding signal, thereby minimizing the time delay required to additionally determine the BSS identifier of the legacy WLAN signal during the CCA process.

[0069] According to another embodiment of the present invention, when a WLAN signal having the same BSS identifier as that of a terminal is received, it is possible to solve the problem of inequality in which different CCA thresholds are applied depending on whether the corresponding WLAN signal includes non-legacy WLAN information. That is, by applying the same CCA thresholds to legacy and non-legacy signals to WLAN signals having the same BSS identifier as that of a terminal, it is possible to maintain fairness in channel occupancy between legacy and non-legacy terminals.

[0070] According to another embodiment of the present invention, CCA can be performed in a shorter time because at least a portion of non-legacy WLAN information, such as BSS identifier information, can be obtained from the legacy preamble before checking the non-legacy preamble.

[0071] According to yet another embodiment of the present invention, when data transmission is performed in a spatial reuse interval of a non-legacy terminal, the data transmission period of the corresponding terminal can be adjusted based on length information extracted from a received radio signal, thereby solving the channel access delay problem of the legacy terminal.

[0072] Furthermore, according to the embodiment of the present invention, it is possible to effectively minimize mutual interference while multiple terminals are simultaneously communicating. [Brief explanation of the drawings]

[0073] [Figure 1] 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Figure 3] FIG. 2 is a block diagram showing the configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. 2 is a block diagram showing the configuration of an access point according to an embodiment of the present invention. [Figure 5]FIG. 1 is a diagram illustrating a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 6] 1 is a diagram illustrating an embodiment of a wireless communication system using the CCA technique. [Figure 7] FIG. 1 illustrates an example of a superimposed BSS environment. [Figure 8] 1A and 1B illustrate various embodiments of a CCA method using BSS identifier information of a received wireless signal. [Figure 9] 1A and 1B illustrate various embodiments of a CCA method using BSS identifier information of a received wireless signal. [Figure 10] 1A and 1B illustrate various embodiments of a CCA method using BSS identifier information of a received wireless signal. [Figure 11] 10 is a diagram illustrating yet another embodiment of a CCA method using whether non-legacy WLAN information can be acquired from a received wireless signal and BSS identifier information. [Figure 12] 10 is a diagram illustrating yet another embodiment of a CCA method using whether non-legacy WLAN information can be acquired from a received wireless signal and BSS identifier information. [Figure 13] 10 is a diagram illustrating yet another embodiment of a CCA method using whether non-legacy WLAN information can be acquired from a received wireless signal and BSS identifier information. [Figure 14] 1 is a diagram showing a frame structure of a wireless LAN signal according to an embodiment of the present invention; [Figure 15] 1 illustrates a method for indicating BSS identifier information according to one embodiment of the present invention. [Figure 16] FIG. 1 is a diagram illustrating an example of a subcarrier configuration used in a legacy preamble of a wireless LAN signal. [Figure 17] FIG. 10 is a diagram illustrating an example of a subcarrier configuration used in a non-legacy WLAN signal. [Figure 18]10 is a diagram illustrating a method of indicating non-legacy WLAN information using a pre-configured bit field of a legacy preamble. [Figure 19] 10 is a diagram illustrating an inequality problem that may occur in legacy terminals when a CCA threshold adjusted according to one embodiment of the present invention is used for channel access. [Figure 20] 1 illustrates a data transmission method for non-legacy terminals to solve the channel access delay problem of legacy terminals. [Figure 21] 1 illustrates a data transmission method for non-legacy terminals to solve the channel access delay problem of legacy terminals. [Figure 22] 1 illustrates a data transmission method for non-legacy terminals to solve the channel access delay problem of legacy terminals. [Figure 23] 1 illustrates a data transmission method for non-legacy terminals to solve the channel access delay problem of legacy terminals. [Figure 24] 10 is a diagram illustrating yet another embodiment showing an inequality problem of legacy terminals that may occur when a CCA threshold adjusted according to an embodiment of the present invention is used for channel access. [Figure 25] 10 is a diagram illustrating an interference problem that may occur when a CCA threshold adjusted according to an embodiment of the present invention is used for channel access. [Figure 26] 10 is a diagram illustrating a data transmission method for non-legacy terminals to minimize interference problems between terminals. [Figure 27] 10 is a diagram illustrating a data transmission method for non-legacy terminals to minimize interference problems between terminals. [Figure 28] 10 is a diagram illustrating yet another interference problem that may occur when a CCA threshold adjusted according to an embodiment of the present invention is used for channel access. [Figure 29] 10 is a diagram illustrating yet another interference problem that may occur when a CCA threshold adjusted according to an embodiment of the present invention is used for channel access. [Figure 30]FIG. 10 is a diagram illustrating yet another embodiment of a data transmission method for non-legacy terminals to minimize interference problems between terminals. DETAILED DESCRIPTION OF THE INVENTION

[0074] The terms used in this specification are currently commonly used and general terms that have been selected as much as possible in consideration of the functions of the present invention, but these may vary depending on the intentions of engineers in the field, customs, or the emergence of new technologies. In addition, in certain cases, the applicant may have arbitrarily selected terms, and in such cases, the meanings thereof will be described in the relevant description of the invention. Therefore, it is clear that the terms used in this specification should be analyzed based on the substantive meanings of the terms and the overall content of this specification, rather than simply the names of the terms.

[0075] Throughout this specification, when a component is referred to as being "connected" to another component, this includes not only when it is "directly connected" to another component, but also when it is "electrically connected" with another component sandwiched between them. Furthermore, when a component is referred to as "comprising" a specific component, this does not mean excluding the other component, but rather includes the other component, unless otherwise specified. In addition, limitations such as "greater than" or "less than" based on a specific critical value may be replaced with "more than" or "less than," respectively, as appropriate, depending on the embodiment.

[0076] This application claims priority based on Korean Patent Registration Nos. 10-2014-0107321, 10-2014-0170812, and 10-2015-0035308, and the examples and descriptions in each of the above priority applications are incorporated herein by reference.

[0077] 1 illustrates a wireless LAN system according to an embodiment of the present invention. A wireless LAN system includes one or more basic service sets (BSSs), which refer to a set of devices that can successfully synchronize and communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), of which FIG. 1 illustrates an infrastructure BSS.

[0078] As shown in FIG. 1, the infrastructure BSs BSS1, BSS2 includes one or more stations STA1, STA2, STA3, STA4, STA5, access points PCP / AP-1, PCP / AP-2 which are stations providing distribution services, and a distribution system (SD) connecting multiple access points PCP / AP-1, PCP / AP-2.

[0079] A station (STA) is any device that includes a Medium Access Control (MAC) and a physical layer interface to the wireless medium according to the IEEE 802.11 standard. In a broad sense, it includes both non-APs and APs. In this specification, the term "terminal" refers to either a non-AP STA or an AP, or both. A station for wireless communication includes a processor and a transmit / receive unit, and, depending on the embodiment, may further include a user interface and a display unit. The processor generates frames to be transmitted over the wireless network, processes frames received over the wireless network, and performs various other processes for controlling the station. The transceiver is functionally connected to the processor and transmits and receives frames over the wireless network for the station.

[0080] An access point (AP) is an entity that provides a connection to a distribution system (DS) via a wireless medium for stations associated with it. In an infrastructure BSS, communication between non-AP stations is generally performed via the AP, but when a direct link is established, direct communication between non-AP stations becomes possible. Meanwhile, in the present invention, the term AP is used as a base including a personal BSS coordination point (PCP), and in a broad sense, it includes all concepts such as a central controller, base station (GS), Node B, base transceiver system (BTS), or site controller.

[0081] A plurality of infrastructure BSSs are interconnected via a distribution system, and the plurality of BSSs connected via the distribution system are referred to as an Extended Service Set (ESS).

[0082] 2 is a diagram showing an independent BSS, which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of FIG. 2, the same or corresponding parts as those in the embodiment of FIG. 1 will not be described again.

[0083] BSS3 shown in Figure 2 is an independent BSS and does not include an AP, so all stations STA6 and STA7 are not connected to an AP. An independent BSS does not allow connections as a distribution system and forms a self-contained network. In an independent BSS, stations STA6 and STA7 are directly connected to each other.

[0084] FIG. 3 is a block diagram showing the configuration of a station 100 according to an embodiment of the present invention.

[0085] As shown, station 100 according to an embodiment of the present invention includes a processor 110 , a transceiver 120 , a user interface 140 , a display unit 150 , and a memory 160 .

[0086] First, the transceiver 120 transmits and receives wireless signals such as WLAN packets and is provided internally or externally in the station 100. According to an embodiment, the transceiver 120 includes at least one transceiver module using different frequency bands. For example, the transceiver 120 includes transceiver modules for different frequency bands such as 2.4 GHz, 5 GHz, and 50 GHz. According to one embodiment, the station 100 includes a transceiver module using a frequency band above 6 GHz and a transceiver module using a frequency band below 6 GHz. Each transceiver module performs wireless communication with an AP or an external station according to the WLAN standard of the frequency band supported by the corresponding transceiver module. The transceiver 120 operates only one transceiver module at a time or multiple transceiver modules simultaneously, depending on the performance and requirements of the station 100. If the station 100 includes multiple transceiver modules, each transceiver module may be provided independently, or multiple modules may be integrated into a single chip.

[0087] Next, the user interface unit 140 is provided in the station 100 and includes various types of input / output means. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the station 100 based on the received user input. Also, the user interface unit 140 performs output based on instructions from the processor 110 using various output means.

[0088] Next, the display unit 150 outputs an image on a display screen. The display unit 150 outputs various display objects, such as content processed by the processor 110 or a user interface based on a control command of the processor 110. The memory 140 also stores control programs and various data used by the station 110. Such control programs include connection programs required for the station 110 to connect to an AP or an external station.

[0089] The processor 110 of the present invention executes various commands or programs to process data within the station 100. The processor 110 also controls each unit of the station 100 and controls data transmission and reception between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection with an AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information regarding the station 100's priorities contained in the communication setup message and requests connection to the AP based on the information regarding the station 100's priorities. The processor 110 of the present invention may refer to a main control unit of the station 100, or, depending on the embodiment, may refer to a control unit for individually controlling some components of the station 100, such as the transceiver 120. The processor 110 controls various operations for transmitting and receiving wireless signals in the station 100 according to an embodiment of the present invention. A specific embodiment of this will be described later.

[0090] The station 100 shown in FIG. 3 is a block diagram according to one embodiment of the present invention, and the separate blocks indicate the logically separated elements of the device. Therefore, the above-described device elements may be implemented on a single chip or multiple chips depending on the device design. For example, the processor 110 and the transceiver 120 may be integrated into a single chip or may be implemented on separate chips. Furthermore, in some embodiments of the present invention, some components of the station 100, such as the user interface 140 and the display unit 150, may be selectively provided in the station 100.

[0091] FIG. 4 is a block diagram showing the configuration of an AP 200 according to an embodiment of the present invention.

[0092] As shown, the AP 200 according to one embodiment of the present invention includes a processor 210, a transceiver 220, and a memory 260. In Fig. 4, the same or corresponding parts of the configuration of the AP 200 as those of the station 100 in Fig. 3 will not be described again.

[0093] Referring to FIG. 4, the AP 200 according to the present invention includes a transceiver unit 220 for operating a BSS in at least one frequency band. As described in the embodiment of FIG. 3, the transceiver unit 220 of the AP 200 also includes multiple transceiver modules that use different frequency bands. That is, the AP 200 according to the embodiment of the present invention includes two or more transceiver modules that use different frequency bands, for example, 2.4 GHz, 5 GHz, and 60 GHz. Preferably, the AP 200 includes a transceiver module that uses a frequency band above 6 GHz and a transceiver module that uses a frequency band below 6 GHz. Each transceiver module performs wireless communication with stations according to the WLAN standard of the frequency band supported by the corresponding transceiver module. The transceiver unit 220 may operate only one transceiver module at a time or multiple transceiver modules simultaneously, depending on the performance and requirements of the AP 200.

[0094] Next, the memory 260 stores control programs used by the AP 200 and various data associated therewith. These control programs include a management program for managing station connections. The processor 210 also controls each unit of the AP 200 and controls data transmission and reception between the units. According to an embodiment of the present invention, the processor 210 executes a program for connecting with a station stored in the memory 260 and transmits a communication setup message to one or more stations. In this case, the communication setup message includes information regarding connection priority conditions of each station. The processor 210 also performs connection setup in response to a station connection request. The processor 210 controls various operations for transmitting and receiving wireless signals of the AP 200 according to an embodiment of the present invention. A specific embodiment of this will be described later.

[0095] FIG. 5 is a diagram showing the CSMA / CA method used in wireless LAN communications.

[0096] A terminal performing wireless LAN communication performs carrier sensing to check whether a channel is occupied before transmitting data. If a wireless signal above a certain strength is detected, the channel is determined to be occupied, and the terminal delays access to the channel. This process is called Clear Channel Assessment (CCA), and the level that determines whether a signal is detected is called the CCA threshold. If a wireless signal received by a terminal that is above the CCA threshold is addressed to the terminal as the receiver, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected on the channel or a wireless signal with a strength below the CCA threshold is detected, the channel is determined to be idle.

[0097] If the channel is determined to be idle, each terminal with data to transmit performs a backoff procedure after an IFS (InterFrame Space), such as an AIFS (Arbitration IFS) or a PIFS (PCF IFS), depending on the status of each terminal. In some embodiments, the AIFS is used as a configuration to replace the conventional DIFS (DCF IFS). Each terminal waits while decreasing the slot time assigned to the corresponding terminal by a random number during the idle interval of the channel, and a terminal that has used up all of its slot time attempts to access the corresponding channel. The period during which each terminal performs the backoff procedure is called a contention window period.

[0098] If a specific terminal successfully accesses the channel, it transmits data through the channel. However, if the terminal attempting access collides with another terminal, the collided terminal is assigned a new random number and performs a backoff procedure again. According to one embodiment, the new random number assigned to each terminal is determined within a range (2*CW) twice the random number range (contention window, CW) previously assigned to the terminal. Meanwhile, each terminal performs a backoff procedure again in the next contention window period to attempt access. At this time, each terminal performs the backoff procedure from the slot time remaining in the previous contention window period. In this way, terminals communicating via a wireless LAN avoid collisions with each other on a specific channel.

[0099] FIG. 6 is a diagram showing an embodiment of a wireless communication system using the CCA technique.

[0100] In wireless communication, such as wireless LAN communication, the occupancy of a channel is detected through CCA, which can be performed using signal detection (SD), energy detection (ED), correlation detection (CD), etc.

[0101] First, signal detection (CCA-SD) is a method for measuring the signal strength of the preamble of a WLAN (i.e., 802.11) frame. While this method allows for stable signal detection, it has the disadvantage of only operating in the initial part of the frame where the preamble is present. According to one embodiment, signal detection is used for CCA on the primary channel in a broadband WLAN. Next, energy detection (CCA_ED) is a method for detecting all signal energy received above a certain threshold. This method is used to detect wireless signals whose preambles are not normally detected, such as Bluetooth and ZigBee signals. This method may also be used for CCA on a secondary channel without continuously tracking the signal. Meanwhile, correlation detection (CCA-CD) is a method for detecting signal levels even in the middle of a WLAN frame, taking advantage of the fact that WLAN signals have a periodic repeating pattern of Orthogonal Frequency Division Multiplex (OFDM) signals. That is, the correlation detection method detects the signal strength for the repetitive pattern of OFDM signal symbols after receiving WLAN data for a given period of time.

[0102] According to an embodiment of the present invention, a terminal's access to a channel may be controlled using a preset CCA threshold for each CCA method. According to the embodiment of FIG. 6, the CCA-ED threshold 10 indicates a preset threshold for performing energy detection, and the CCA-SD threshold 30 indicates a preset threshold for performing signal detection. Furthermore, the receiver sensitivity (RX Sensitivity) 50 indicates the minimum signal strength at which the terminal can decode a wireless signal. According to the embodiment, the receiver sensitivity 50 is set to a level equal to or lower than the CCA-SD threshold 30 depending on the terminal's performance and settings. Furthermore, the CCA-ED threshold 10 is set to a level higher than the CCA-SD threshold 30. For example, the CCA-ED threshold 10 is set to -63 dBm, and the CCA-SD threshold 30 is set to -82 dBm. However, the present invention is not limited to this, and the CCA-ED threshold value 10 and the CCA-SD threshold value 30 are set differently depending on whether they are threshold values for the seed channel or not, the bandwidth of the channel on which CCA is performed, and the like.

[0103] According to the embodiment of Figure 6, each terminal measures the signal strength (RX Received Signal Strength Indicator, RS RSSI) of the received wireless signal and determines the channel state based on the comparison result between the measured received signal strength and each of the set CCA threshold values.

[0104] First, if a wireless signal 350 with a receiver sensitivity of 50 or higher received on a specific channel has a received signal strength (RX RSSI) below the CCA-SD threshold of 30, the channel is determined to be idle. Therefore, the received signal is not processed or protected by the terminal, and each terminal attempts to access the channel using the method described in FIG. 5.

[0105] If a WLAN signal 330 having a received strength (RX RSSI) greater than or equal to the CCA-SD threshold value of 30 is received on a specific channel, the channel is determined to be occupied. Therefore, the terminal receiving the signal delays access to the channel. According to one embodiment, the terminal determines whether the signal is a WLAN signal by using the signal pattern of the preamble portion of the received wireless signal. According to the embodiment of FIG. 6, each terminal determines that the channel is occupied even if it receives a WLAN signal from not only the same BSS as the terminal but also a WLAN signal from another BSS.

[0106] Meanwhile, when a wireless signal 310 having a received signal strength (RX RSSI) equal to or greater than the CCA-ED threshold value of 10 is received from a specific channel, the corresponding channel is determined to be occupied. In this case, even when a wireless signal other than a WLAN signal is received, the terminal determines that the corresponding channel is occupied if the received signal strength of the corresponding signal is equal to or greater than the CCA-ED threshold value of 10. Therefore, the terminal receiving the corresponding signal delays access to the channel.

[0107] Figure 7 is a diagram showing an example of an overlapping BSS (OBSS) environment. In Figure 7, in BSS-1 operated by AP-1, station 1 STA-1 and station 2 STA-2 AP-1 are associated, and in BSS-2 operated by AP-2, station 3 STA-3 and station 4 STA-4 are associated with AP-2. In the overlapping BSS environment of Figure 7, at least a portion of the communication coverage of BSS-1 and BSS-2 overlaps.

[0108] As shown in Figure 7, when STA-3 transmits upload data to AP-2, it may continuously interfere with STA-2 of nearby BSS-1. In this case, interference that occurs when BSS-1 and BSS-2 use the same frequency band (e.g., 2.4 GHz, 5 GHz, etc.) and the same primary channel is called co-channel interference (CCI). Furthermore, interference that occurs when BSS-1 and BSS-2 use adjacent primary channels is called adjacent channel interference (ACI). The CCI or ACI is received at a signal strength higher than the CCA threshold (e.g., CCA-SD threshold) of STA-2 depending on the distance between STA-2 and STA-3. If such interference is received at a strength higher than the CCA threshold by STA-2, STA-2 recognizes the channel as occupied and delays the upload data transmission from AP-1. However, since STA-2 and STA-3 are stations belonging to different BSSs, increasing the CCA threshold of STA-2 allows STA-2 and STA-3 to simultaneously upload to AP-1 and AP-2, respectively, thereby improving the effect of spatial reuse.

[0109] Meanwhile, in Figure 7, the updater transmission of STA-3 in BSS-2 also interferes with STA-4, which belongs to the same BSS-2. In this case, if the CCA threshold of STA-4 is increased to the same value as that of STA-2, STA-3 and STA-4, which belong to the same BSS, may simultaneously transmit upload data to AP-2, resulting in a collision. Therefore, in order to increase the CCA threshold for a given interference, it is necessary to determine whether the interference is caused by a signal belonging to the same BSS or a signal belonging to another BSS. To this end, each terminal should check the BSS identifier of the WLAN signal or other different types of information that can distinguish the BSS. Furthermore, it is preferable that such BSS information be checked within a short time period during which the CCA process is performed.

[0110] 8 to 13 are diagrams illustrating various embodiments of the CCA method according to the present invention. In the embodiments of FIGS. 8 to 13, the shaded areas indicate radio signals that are received but ignored by the UE, i.e., unprotected radio signals. In other words, when a radio signal corresponding to a shaded area is received, the UE determines that the corresponding channel is idle. On the other hand, when a radio signal corresponding to an unshaded area is received, the UE determines that the corresponding channel is occupied. In this case, the RX Sensitivity is set to a level equal to or lower than the CCA-SD threshold depending on the performance and settings of the UE. In addition, the CCA-ED threshold is set to a level higher than the CCA-SD threshold. In each embodiment described below, the individual processes described in FIG. 5 are performed based on the result of determining whether the channel is occupied.

[0111] 8 to 10, the terminal measures the received signal strength (RX RSSI) of a received wireless signal and determines whether the signal is a WLAN signal. If the received signal is a WLAN signal having BSS identifier information according to various embodiments described below, the terminal extracts the BSS identifier information from the signal and determines whether the extracted BSS identifier information is the same as the BSS identifier information of the terminal.

[0112] 8, a CCA threshold for a received wireless signal is determined based on whether the received wireless signal is a WLAN signal having the same BSS identifier as the BSS identifier of the terminal. In the embodiment of the present invention, the BSS identifier of the terminal refers to the BSS identifier information assigned to the terminal, and if the terminal is a non-AP STA, refers to the identifier information of the AP to which the terminal is associated or to which the terminal is to associate (e.g., the MAC address of the AP) or abbreviated information thereof. In this case, the terminal receives the BSS identifier information from the AP, and the received BSS identifier information is stored in the terminal.

[0113] 8, if a received wireless signal of a specific channel is a WLAN signal with a receiver sensitivity of 50 or higher and a received signal strength (RX RSSI) of 30 or lower, the availability of the channel is determined based on whether the corresponding signal is a WLAN signal with the same BSS identifier as the terminal. If the BSS identifier information extracted from the wireless signal is different from the terminal's BSS identifier information (i.e., if it is an OBSS WLAN signal 452), the corresponding channel is determined to be idle. However, if the BSS identifier information extracted from the wireless signal is the same as the terminal's BSS identifier information (i.e., if it is an MYBSS WLAN signal 454), the corresponding channel is determined to be occupied.

[0114] Meanwhile, if the received wireless signal of a specific channel is a WLAN signal 430 having a received signal strength (RX RSSI) between the CCA-SD threshold of 30 and the CCA-ED threshold of 10, the corresponding channel is determined to be occupied. In this case, the terminal receiving the WLAN signal 430 determines the channel on which the signal is received to be occupied not only when the corresponding signal has the same BSS identifier information as the terminal, but also when the corresponding signal has a different BSS identifier information.

[0115] In the energy detection process, if the wireless signal of a specific channel received by the terminal is a wireless signal 410 having a received signal strength (RX RSSI) equal to or greater than the CCA-ED threshold value of 10, the corresponding channel is determined to be occupied. As described above, even if a wireless signal other than a WLAN signal is received, the terminal determines that the corresponding channel is occupied if the received signal strength (RX RSSI) of the wireless signal is equal to or greater than the CCA-ED threshold value of 10.

[0116] 8, the CCA threshold applied to a WLAN signal having the same BSS identifier as the UE has a different level from the CCA threshold applied to a WLAN signal having a different BSS identifier from the UE. According to one embodiment, the CCA threshold applied to a WLAN signal having a different BSS identifier from the UE is set to a higher level than the CCA threshold applied to a WLAN signal having the same BSS identifier as the UE. According to the embodiment of FIG. 8, the preset CCA-SD threshold of 30 is applied to the CCA threshold for a WLAN signal having a different BSS identifier from the UE, and the UE's receiving sensitivity level of 50 is applied to the CCA threshold for a WLAN signal having the same BSS identifier as the UE.

[0117] 9 and 10 are diagrams illustrating another embodiment of a CCA method using BSS identifier information. In the embodiment of FIG. 9 and 10, the same or corresponding parts as the embodiment of FIG. 8 will not be described again.

[0118] First, according to the embodiment of FIG. 9, the CCA threshold for a received wireless signal is determined based on whether the received wireless signal is a WLAN signal having the same BSS identifier as the BSS identifier of the terminal.

[0119] 9, if the received signal strength (RXRSSI) of a received wireless signal of a specific channel is greater than or equal to 50 in sensitivity and less than the CCA-SD threshold of 40, the corresponding channel is determined to be in an idle state. In this case, the terminal determines that the channel on which the corresponding signal is received is in an idle state both when the received signal is a WLAN signal 454 having the same BSS identifier information as the terminal and when the received signal is a WLAN signal 452 having different identifier information.

[0120] However, if the received wireless signal of a specific channel is a WLAN signal having a received signal strength (RX RSSI) between the first CCA-SD threshold of 40 and the second CCA-SD threshold of 20, the channel's occupancy is determined based on whether the corresponding signal is a WLAN signal having the same BSS identifier as the terminal. If the BSS identifier information extracted from the wireless signal is different from the terminal's BSS identifier information (i.e., if it is an OBSS WLAN signal 442), the corresponding channel is determined to be idle. However, if the BSS identifier information extracted from the wireless signal is the same as the terminal's BSS identifier information (i.e., if it is an MYBSS WLAN signal 444), the corresponding channel is determined to be occupied.

[0121] In the embodiment of Figure 9, the second CCA-SD threshold value 20 is used to perform signal detection for WLAN signals having BSS identifier information different from that of the terminal, and is set to a level greater than the first CCA-SD threshold value 40 and less than or equal to the CCA-ED threshold value.

[0122] Meanwhile, if the received wireless signal of a specific channel is a WLAN signal 420 having a received signal strength (RX RSSI) between the second CCA-SD threshold of 20 and the second CCA-ED threshold of 10, the corresponding channel is determined to be occupied. In this case, the terminal receiving the WLAN signal 420 determines the channel on which the corresponding signal is received to be occupied not only when the corresponding signal has the same BSS identifier information as the terminal, but also when the corresponding signal has a different BSS identifier information.

[0123] In the energy detection process, if the wireless signal of a specific channel received by the terminal is a wireless signal 410 having a received signal strength (RX RSSI) equal to or greater than the CCA-ED threshold value of 10, the corresponding channel is determined to be occupied. As described above, even if a wireless signal other than a WLAN signal is received, the terminal determines that the corresponding channel is occupied if the received signal strength (RX RSSI) of the wireless signal is equal to or greater than the CCA-ED threshold value of 10.

[0124] 9, the CCA threshold applied to a WLAN signal having the same BSS identifier as the UE has a different level from the CCA threshold applied to a WLAN signal having a different BSS identifier from the UE. That is, a preset first CCA-SD threshold of 40 is applied as the CCA threshold for a WLAN signal having the same BSS identifier as the UE, and a preset second CCA-SD threshold of 20 is applied as the CCA threshold for a WLAN signal having a different BSS identifier from the UE. Here, the second CCA-SD threshold of 20 is set to be higher than the first CCA-SD threshold of 40 and lower than or the same level as the CCA-ED threshold.

[0125] Next, according to the embodiment of FIG. 10, if the received signal strength (RXRSSI) of a wireless signal of a specific channel is greater than or equal to 50, signal detection is performed based on whether the corresponding signal is a WLAN signal having the same BSS identifier information as the corresponding terminal.

[0126] In the signal detection process, if the received signal strength (RX RSSI) of the wireless signal received by the terminal is equal to or greater than 50 in sensitivity and is a WLAN signal 453 having the same BSS identifier information as the terminal, the corresponding channel is determined to be in an occupied state. However, if the received signal strength (RX RSSI) of the received wireless signal is equal to or greater than 50 in sensitivity and is a WLAN signal 451 having a different BSS identifier information from the terminal, the corresponding channel is determined to be in an idle state.

[0127] Meanwhile, in the energy detection process, if the wireless signal received by the terminal is a wireless signal 410 having a received signal strength (RX RSSI) greater than or equal to the CCA-ED threshold value of 10, the corresponding channel is determined to be occupied. The terminal determines that the corresponding channel is occupied regardless of whether the corresponding signal is a WLAN signal having the same BSS identifier information as the terminal, and regardless of whether the corresponding signal is a WLAN signal. Therefore, if a WLAN signal having a BSS identifier information different from that of the terminal is received at a level higher than the CCA-ED threshold value of 10, the corresponding channel is determined to be occupied by the energy detection process.

[0128] 10, in the signal detection process, the terminal determines whether to occupy a channel based on whether the received wireless signal is a WLAN signal having the same BSS identifier as the terminal, without using a separately set CCA-SD threshold. However, the terminal uses a preset CCA-ED threshold of 10 for energy detection, thereby avoiding collision with a WLAN signal having a different BSS identifier from the terminal.

[0129] 11 to 13 are diagrams illustrating other embodiments of a CCA method using whether non-legacy WLAN information can be acquired and BSS identifier information. In each embodiment of FIG. 11 to 13, a terminal measures the received signal strength (RX RSSI) of a received wireless signal and determines whether the corresponding signal is a WLAN signal. If the received signal is a WLAN signal having BSS identifier information according to various embodiments described below, the terminal extracts the BSS identifier information from the corresponding signal and determines whether the extracted BSS identifier information is the same as the BSS identifier information of the corresponding terminal.

[0130] In addition, the terminal acquires at least one of legacy WLAN information and non-legacy WLAN information from the received wireless signal. Through this, the terminal determines whether the received wireless signal contains only legacy WLAN information or both legacy and non-legacy WLAN information. According to one embodiment, the terminal acquires at least one of legacy WLAN information and non-legacy WLAN information using preamble information of the received wireless signal. If non-legacy WLAN information is acquired from the corresponding signal, the BSS identifier information of the wireless signal is extracted from the non-legacy WLAN information. However, the present invention is not limited thereto, and the BSS identifier information may be extracted from the legacy WLAN information according to various embodiments described below. According to one embodiment of the present invention, the BSS identifier information referenced for CCA may be included in the non-legacy WLAN information, but the received wireless signal may not contain non-legacy WLAN information. That is, if a received wireless signal does not include BSS identifier information referenced for performing CCA according to an embodiment of the present invention, the BSS identifier information may not be extracted from the corresponding signal. In such a case, the BSS identifier information for performing CCA is set to a pre-specified value. According to another embodiment, if the received wireless signal is a non-legacy WLAN signal that does not include BSS identification information according to an embodiment of the present invention, the BSS identifier information of the corresponding signal is estimated using other information of the corresponding signal, such as a PBSSID (Partial BSSID), a PAID (Partial Association ID), PHY layer header information, a specific preamble signal pattern, etc. In the embodiments of Figures 11 to 13, duplicated descriptions of parts that are the same as or correspond to the above-mentioned embodiments will be omitted.

[0131] First, referring to FIG. 11, if the received wireless signal of a specific channel is a WLAN signal having a receiving sensitivity of 50 or more and a received signal strength (RX RSSI) of 40 or less, which is the first CCA-SD threshold, whether the channel can be occupied is determined based on whether the corresponding signal is a WLAN signal having the same BSS identifier information as the terminal.

[0132] If the BSS identifier information extracted from the wireless signal differs from the terminal's BSS identifier information (i.e., if it is an OBSS WLAN signal), the corresponding channel is determined to be idle. In this case, the OBSS WLAN signal 552 is classified into an OBSS non-legacy WLAN signal from which non-legacy WLAN information is acquired, and an OBSS legacy WLAN signal from which non-legacy WLAN information is not acquired. The terminal determines that the corresponding channel is idle both when an OBSS non-legacy WLAN signal is received and when an OBSS legacy WLAN signal is received.

[0133] On the other hand, if the BSS identifier information extracted from the wireless signal is the same as the BSS identifier information of the terminal (i.e., if it is a MYBSS WLAN signal), the corresponding channel is determined to be occupied. Similarly, the MYBSS WLAN signal 2 is divided into a MYBSS non-legacy WLAN signal 558 from which non-legacy WLAN information is acquired, and a MYBSS legacy WLAN signal 556 from which non-legacy WLAN information is not acquired. The terminal determines that the corresponding channel is occupied both when it receives the MYBSS non-legacy WLAN signal 558 and when it receives the MYBSS legacy WLAN signal 556.

[0134] Meanwhile, if the received wireless signal of a specific channel is a WLAN signal having a received signal strength (RX RSSI) between the first CCA-SD threshold of 40 and the second CCA-SD threshold of 20, the channel occupancy is determined based on whether the corresponding signal includes non-legacy WLAN information and whether it has the same BSS identifier information as the terminal. According to one embodiment, the first CCA-SD threshold of 40 is set to the same level as the CCA-SD threshold applied to legacy terminals, and the second CCA-SD threshold of 20 is set to a level higher than the first CCA-SD threshold of 40 and lower than or the same as the CCA-ED threshold.

[0135] If non-legacy WLAN information is acquired from a WLAN signal and the BSS identifier information of the corresponding signal is different from the BSS identifier information of the terminal (i.e., non-legacy BSS signal 542), the corresponding channel is determined to be idle. However, in other cases, i.e., if non-legacy WLAN information is not acquired from the wireless signal (i.e., legacy signal) or the BSS identifier information is the same as the BSS identifier information of the corresponding signal (i.e., MYBSS signal), the corresponding channel is determined to be occupied. More specifically, cases in which a channel is determined to be occupied include: i) when non-legacy WLAN information is not acquired from the wireless signal and the BSS identifier information of the corresponding signal is different from the BSS identifier information of the terminal (i.e., non-legacy BSS signal 544); ii) when non-legacy WLAN information is not acquired from the wireless signal and the BSS identifier information of the corresponding signal is the same as the BSS identifier information of the terminal (i.e., legacy MYBSS signal 546); and iii) when non-legacy WLAN information is acquired from the wireless signal and the BSS identifier information of the corresponding signal is the same as the BSS identifier information of the terminal (i.e., non-legacy MYBSS signal 548).

[0136] In other words, if non-legacy WLAN information is not acquired from a wireless signal, the corresponding channel is determined to be occupied. However, if non-legacy WLAN information is acquired from a wireless signal, whether the channel is occupied is determined based on whether the BSS identifier information of the corresponding signal is the same as the BSS identifier information of the terminal. Therefore, according to an embodiment of the present invention, when non-legacy WLAN information is acquired from a wireless signal, whether the corresponding channel is occupied is determined based on the BSS identifier information of the wireless signal. According to one embodiment, if non-legacy WLAN information is not acquired from a wireless signal, the BSS identifier information referenced for performing the CCA of the present invention may not be extracted from the corresponding signal. In this case, the terminal determines that the channel is occupied regardless of whether BSS identifier information is extracted from the corresponding signal.

[0137] The signal detection process is performed by referring to the preamble of the received wireless signal. According to an embodiment, if the channel is determined to be occupied during signal detection, the UE may not access the channel during a frame transmission time of the wireless signal even if the received signal strength (RX RSSI) falls below the first CCA-SD threshold value of 40 while receiving the protected wireless signal.

[0138] Meanwhile, if the received wireless signal of a specific channel is a WLAN signal 520 between the second CCA-SD threshold of 20 and the CCA-ED threshold of 10, the corresponding channel is determined to be occupied. In this case, the terminal receiving the WLAN signal 520 determines that the channel on which the corresponding signal is received is occupied, regardless of whether non-legacy WLAN information is acquired from the corresponding signal and whether the corresponding signal is a WLAN signal having the same BSS identifier information as the terminal.

[0139] In the energy detection process, if the wireless signal of a specific channel received by the terminal is a wireless signal 510 having a CCA-ED threshold value of 10 or more, the terminal determines that the corresponding channel is occupied. As described above, even if the terminal receives a wireless signal other than a WLAN signal, the terminal determines that the corresponding channel is occupied if the received signal strength (RX RSSI) of the wireless signal is equal to or greater than the CCA-ED threshold value of 10.

[0140] Next, according to the embodiment of Figure 12, if the received wireless signal of a specific channel is a WLAN signal having a receiving sensitivity of 50 or more and a received signal strength (RX RSSI) of less than the first CCA-SD threshold value of 40, whether the channel can be occupied is determined based on whether the corresponding signal includes non-legacy WLAN information and whether it has the same BSS identifier information as the terminal.

[0141] If non-legacy WLAN information is acquired from a wireless signal and the BSS identifier information of the corresponding signal is the same as the BSS identifier information of the terminal (i.e., non-legacy WLAN information MYBSS558 signal), the corresponding channel is determined to be occupied. However, in other cases, i.e., if the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal (i.e., BSS signal) or if non-legacy WLAN information is not acquired from the corresponding signal (i.e., legacy signal), the corresponding channel is determined to be idle. More specifically, a channel is determined to be idle when: i) non-legacy WLAN information is acquired from the wireless signal and the BSS identifier information of the corresponding signal is different from the BSS identifier information of the terminal (i.e., when it is an OBSS signal 552); ii) non-legacy WLAN information is not acquired from the wireless signal and the BSS identifier information of the corresponding signal is different from the BSS identifier information of the terminal (i.e., when it is a legacy OBSS signal 554); and iii) non-legacy WLAN information is not acquired from the wireless signal and the BSS identifier information of the corresponding signal is the same as the BSS identifier information of the terminal (i.e., when it is a legacy MYBSS signal 556).

[0142] That is, if non-legacy WLAN information is not acquired from a wireless signal, the corresponding channel is determined to be idle. However, if non-legacy WLAN information is acquired from a wireless signal, whether the channel is occupied is determined based on whether the BSS identifier of the corresponding signal is the same as the BSS identifier of the terminal. According to the embodiment of FIG. 12, if non-legacy WLAN information is acquired from a wireless signal and the BSS identifier of the corresponding signal differs from the BSS identifier of the terminal, a preset CCA threshold of 20 is used for CCA of the corresponding channel. However, if non-legacy WLAN information is acquired from a wireless signal and the BSS identifier of the corresponding signal is the same as the BSS identifier of the terminal, the corresponding channel is determined to be occupied without setting a separate CCA threshold if the corresponding signal has a received signal strength of 50 or more. According to one embodiment, if non-legacy WLAN information is not acquired from a wireless signal, the BSS identifier referenced for performing the CCA of the present invention may not be extracted from the corresponding signal. At this time, the terminal determines that the channel is idle regardless of whether BSS identifier information is extracted from the corresponding signal.

[0143] According to the embodiment of Figure 12, BSS identifier information referenced for CCA is included in non-legacy WLAN information, and efficient CCA can be performed even if the received WLAN signal does not include such non-legacy WLAN information. That is, if the received wireless signal is a legacy wireless signal from which the BSS identifier information is not extracted, the corresponding channel is determined to be idle or occupied based on the received signal strength of the corresponding signal, thereby minimizing the time delay required to determine whether the BSS identifier of the legacy WLAN signal is actually the same as the BSS identifier of the terminal. That is, the terminal additionally checks the BSS identifier information to determine the idle / occupied state of the channel only if the wireless signal is a non-legacy WLAN signal.

[0144] Next, according to the embodiment of FIG. 13, if the received signal strength (RX RSSI) of a received wireless signal of a specific channel is greater than or equal to 50 in receiver sensitivity and less than or equal to 40 in first CCA-SD threshold, the corresponding channel is determined to be in an idle state. In this case, the terminal determines the corresponding channel to be in an idle state regardless of whether the received signal includes non-legacy WLAN information and whether the received signal has the same BSS identifier as the terminal. Also, according to the embodiment of FIG. 13, if non-legacy WLAN information is acquired from a wireless signal and the BSS identifier of the corresponding signal is the same as the BSS identifier of the terminal, the first CCA-SD threshold of 40 is used for CCA of the corresponding channel. However, if non-legacy WLAN information is acquired from a wireless signal and the BSS identifier of the corresponding signal is different from the BSS identifier of the terminal, the second CCA-SD threshold of 20, which is higher than the first CCA-SD threshold of 40, is used for CCA of the corresponding channel.

[0145] 13, when a WLAN signal having the same BSS identifier as a UE is received, the problem of applying different CCA thresholds depending on whether the WLAN signal contains non-legacy WLAN information can be resolved. In other words, by applying the same CCA threshold to both legacy and non-legacy MYBSS signals, fairness in channel occupancy between legacy and non-legacy UEs can be maintained.

[0146] Meanwhile, in the embodiments of Figures 12 and 13, when a wireless signal having a received signal strength (RX RSSI) greater than the first CCA-SD threshold value of 40 is received, the CCA process is performed in the same manner as in the embodiment of Figure 11 described above.

[0147] FIG. 14 is a diagram illustrating a frame structure of a WLAN signal according to an embodiment of the present invention. Referring to FIG. 14, the WLAN signal according to an embodiment of the present invention includes a legacy preamble 710 for a legacy terminal (e.g., a terminal using 802.11a / g) and a non-legacy preamble 720 for a non-legacy terminal (e.g., an 802.11ax terminal). First, the legacy preamble 710 includes legacy radio information that can be decoded by a legacy terminal, such as an L-STF, an L-LTF, and an L-SIG field. Second, the non-legacy preamble 720 can be decoded only by a non-legacy terminal. The non-legacy preamble 720 may include non-legacy WLAN information that can be decoded by a legacy terminal, and the non-legacy WLAN information cannot be decoded by a legacy terminal. Meanwhile, the legacy preamble 710 may include at least a portion of non-legacy WLAN information that can be decoded by a non-legacy terminal, depending on the embodiment. Furthermore, the non-legacy preamble 720 may include information in which at least one field of the legacy preamble 710, for example, the L-SIG field, is partially or entirely repeated.

[0148] According to one embodiment of the present invention, BSS identifier information referenced for performing CCA is included in the non-legacy preamble 720 as non-legacy WLAN information. In this case, the BSS identifier information is extracted from a preset bit field in the non-legacy preamble 720. Meanwhile, according to another embodiment of the present invention, the BSS identifier information is extracted from additional information in the legacy preamble 710. For example, the legacy preamble 710 includes non-legacy WLAN information via an additional subcarrier set, as described below, and the BSS identifier information is obtained from the non-legacy WLAN information included in the legacy preamble 710. According to yet another embodiment of the present invention, the BSS identifier information may be extracted from a preset bit field in the legacy preamble 710. In this case, the preset bit field in the legacy preamble 710 may be a bit field set for legacy terminals, and the value of the corresponding bit field may be used as BSS identifier information under certain conditions, as described below.

[0149] FIG. 15 is a diagram illustrating a method for representing BSS identifier information according to an embodiment of the present invention. According to an embodiment of the present invention, the BSS identifier information is represented as a preset bit field in the non-legacy preamble 720 of FIG. 14. According to an embodiment of the present invention, the BSS identifier information is abbreviated information of a BSS identifier assigned to each BSS and has fewer bits than the actual BSS identifier. For example, if a BSS identifier is represented as 24-bit information in a specific WLAN system, the BSS identifier information is represented as a bit field of a preset length ranging from 1 bit to 23 bits. In the present invention, the BSS identifier information is information obtained by classifying the actual BSS identifier into preset categories and is also referred to as a BSS color. Methods for actually obtaining the abbreviated BSS color from the BSS identifier include a method using a combination of bit values at preset positions of the BSS identifier and a method using a result value obtained by applying a preset hash function to the BSS identifier.

[0150] Figure 15 shows an example of this, showing the result of obtaining a BSS color using the last three bits of the BSS identifier. In this way, the BSS color is included in the preamble of a WLAN signal with less information than the actual BSS identifier, allowing each terminal to quickly and efficiently determine whether the received WLAN signal has the same BSS identifier as the terminal. This BSS identifier is represented by pre-defined bits in the non-legacy preamble.

[0151] Meanwhile, according to one embodiment of the present invention, the non-legacy preamble 720 includes a repeated L-SIG field, which is configured to have at least some bits identical to those of the L-SIG field of the legacy preamble 710. In this case, the bits of the repeated L-SIG field that are different from those of the L-SIG field of the legacy preamble 710 indicate BSS identifier information, system bandwidth information, non-legacy WLAN system information, channel information, etc.

[0152] According to additional embodiments of the present invention, additional information is transmitted through a modulation method applied to a repeated L-SIG field. That is, the repeated L-SIG field may be expressed using the same modulation value as the L-SIG field of the legacy preamble 710, or may be expressed using an opposite modulation value. Here, the opposite modulation value is represented by a phase transition between the modulation symbols transmitted in the L-SIG of the legacy preamble 710 and the modulation symbols of the repeated L-SIG, enabling additional information transmission through the amount of phase change. Specifically, if the L-SIG of the legacy preamble 710 and the repeated L-SIG are multiplied by (1,1) and transmitted, the symbols of both fields have the same phase. If they are multiplied by (1,-1) and transmitted, a 180-degree phase transition occurs between the symbols of the repeated L-SIG and the symbols of the legacy preamble 710. In this case, specific flag information for non-legacy WLAN information is determined depending on whether the repeated L-SIG field is expressed with the same modulation value as the L-SIG field of the legacy preamble 710. For example, whether the SIG-A field of the non-legacy preamble is of variable length, whether the non-legacy preamble includes a SIG-B field, and whether a specific bit field of the non-legacy preamble (or legacy preamble) indicates BSS identifier information are determined.

[0153] 16 and 17 are diagrams illustrating a method for acquiring non-legacy WLAN information using an additional subcarrier set of a WLAN signal according to another embodiment of the present invention.

[0154] First, FIG. 16 illustrates an example of a subcarrier configuration used in a legacy preamble of a WLAN signal. According to one embodiment of the present invention, the subcarrier set of the legacy preamble of a non-legacy WLAN signal is configured in the same manner as the subcarrier set of the legacy WLAN signal. That is, the subcarrier set of the legacy preamble is configured with a total of 52 subcarriers, including four pilot subcarriers and 48 data subcarriers, in a 20 MHz bandwidth. In this case, if the subcarrier numbers are set as -26, -25, ..., -2, -1, 1, 2, ..., 25, 26, the subcarriers numbered -21, -7, 7, and 21 are used as pilot subcarriers, and the remaining subcarriers are used as data subcarriers. This basic subcarrier configuration is necessary to maintain compatibility between legacy WLAN systems (e.g., 802.11a / g) and non-legacy WLAN systems (e.g., 802.11ax) in an environment where they coexist. In other words, by making the legacy preamble of not only the legacy signal but also the non-legacy WLAN signal have the subcarrier configuration shown in FIG. 16, it is possible to provide backward compatibility with legacy terminals.

[0155] FIG. 17 shows an embodiment of a subcarrier configuration used in a non-legacy WLAN signal. With the development of filter amplifiers and other technologies used in terminals, non-legacy WLAN systems can use additional subcarriers without interference from adjacent bandwidths. Referring to FIG. 17, the subcarriers of a non-legacy WLAN signal according to an embodiment of the present invention include a first subcarrier set 800 and a second subcarrier set 820. More specifically, the first subcarrier set 800 is configured identically to the subcarrier set of the legacy WLAN signal shown in FIG. 16. Furthermore, the second subcarrier set 820 is a subcarrier set different from the first subcarrier set 800. According to one embodiment, the second subcarrier set 820 includes four additional subcarriers, two at the upper and two at the lower indexes of the first subcarrier set 800. According to the embodiment of FIG. 17, the non-legacy WLAN signal uses the same positions and number of pilot subcarriers as the legacy WLAN signal, resulting in the use of 52 data subcarriers, an increase of four from the conventional 48. According to one embodiment, this subcarrier configuration is used after the legacy preamble part of the non-legacy WLAN signal. A non-legacy terminal acquires a total of 56 subcarriers from the non-legacy preamble and data field of the received non-legacy WLAN signal.

[0156] According to one embodiment of the present invention, the second subcarrier set 820 included in the non-legacy preamble indicates BSS identifier information, system bandwidth information, non-legacy WLAN system information, channel information, etc. In this case, a separate parity bit for a parity check of the second subcarrier set 820 is included in the non-legacy preamble. According to one embodiment, when the non-legacy preamble includes a repeated L-SIG field as described above, the BSS identifier information, system bandwidth information, non-legacy WLAN system information, channel information, etc. are represented via the second subcarrier set 820 of the repeated L-SIG field.

[0157] Meanwhile, according to another embodiment of the present invention, the subcarrier configuration of Fig. 17 is extended to be applied to the legacy preamble of the non-legacy WLAN signal. That is, the legacy preamble of the non-legacy WLAN signal additionally includes a second subcarrier set 820 and transmits non-legacy WLAN information via the second subcarrier set 280. In this case, legacy terminals cannot acquire information from the second subcarrier set 820, but non-legacy terminals can acquire additional information from the second subcarrier set 820 of the legacy preamble.

[0158] For example, assuming that the second subcarrier set 820 additionally used in the legacy preamble includes four subcarriers, the indices (i.e., subcarrier numbers) of the corresponding subcarriers are set to -28, -27, 28, and 28, respectively, as shown in FIG. 17. In this case, if the BPSK modulation scheme is used for the legacy preamble and the same modulation scheme is applied to the second subcarrier set, a total of four bits of information are additionally transmitted. Similarly, if the QPSK modulation scheme is applied to the second subcarrier set, a total of eight bits of information are additionally transmitted. In this case, the parity bits for parity check are included in the non-legacy preamble in the second subcarrier set included in the legacy preamble.

[0159] According to a further embodiment of the present invention, only a portion of the total bits indicated by the second subcarrier set 820 of the legacy preamble are used to transmit additional information. For example, the second subcarrier set 820 uses only a portion of the bits to transmit additional information for compatibility with the parity check of the legacy preamble. That is, for compatibility with the parity bits conventionally used in L-SIG, the information added by the second subcarrier set 820 has even parity. When the BPSK modulation scheme is used, the information that can be transmitted via the second subcarrier set 820 is a total of three bits of information: 1010, 0101, 1100, 0011, 1001, 0110, 1111, and 0000.

[0160] According to another embodiment, certain bits of the second subcarrier set 820 are used as parity check bits, and the remaining bits are used to transmit additional information. For example, three of the four bits of the second subcarrier set 820 are used to transmit additional information, and one bit is used as a parity bit. In this case, the parity bit of the second subcarrier set 820 may be used for parity check for the bits added by the second subcarrier set 820, or may be used for parity check for the entire L-SIG including the second subcarrier set 820. In this case, parity check may be performed using the conventional parity bit of the L-SIG for legacy WLAN signals, and parity check may be performed using both the conventional parity bit of the L-SIG and the parity bit of the second subcarrier set 820 for non-legacy WLAN signals, thereby enabling more reliable parity check. Also, according to another embodiment, the non-legacy WLAN information added by the second subcarrier set 820 may be parity checked using a reserved bit of the L-SIG.

[0161] In this way, when additional information for a non-legacy terminal is transmitted via the second subcarrier set 820 of the legacy preamble, the non-legacy terminal can acquire the additional information more quickly from the legacy preamble of the received WLAN signal and use this information to reduce initial connection delay and detection of unnecessary preambles, headers, packets, etc. Also, according to an embodiment of the present invention, the non-legacy terminal acquires non-legacy WLAN information from the second subcarrier set 820 of the legacy preamble, and the acquired non-legacy WLAN information includes the above-mentioned BSS identifier information, system bandwidth information, non-legacy WLAN system information, channel information, etc. If the non-legacy terminal acquires the second subcarrier set 820 from the legacy preamble of the received WLAN signal, it recognizes that the corresponding WLAN signal includes non-legacy WLAN information.

[0162] 17 has been described with reference to an embodiment in which the second subcarrier set 820 includes four additional data subcarriers, but the present invention is not limited to this, and other numbers of subcarriers may be included in the second subcarrier set 820. Furthermore, the embodiment of FIG. 17 is applicable not only when the bandwidth of the WLAN signal is 20 MHz, but also when other bandwidths such as 40 MHz, 80 MHz, and 160 MHz are used.

[0163] FIG. 18 illustrates a method for indicating non-legacy WLAN information using a preset bit field of a legacy preamble according to yet another embodiment of the present invention.

[0164] According to an additional embodiment of the present invention, non-legacy WLAN information is extracted from a preset bit field of a legacy preamble under specific conditions. FIG. 18 illustrates one example of this, showing a rate bit field included in the L-SIG of a legacy preamble. As shown in the figure, in a conventional legacy preamble, the fourth bit of the rate bit field is always set to 1. Therefore, information regarding the data rate, modulation method, and code rate of the legacy WLAN signal is obtained through the values of the first three bits of the rate bit field. Therefore, according to an embodiment of the present invention, it is possible to determine whether a corresponding rate bit field indicates non-legacy WLAN information based on the value of the fourth bit of the rate bit field. That is, if the fourth bit of the rate bit field has a value of 1, the corresponding rate bit field indicates legacy information, i.e., the data rate, modulation method, and code rate. However, if the fourth bit of the rate bit field has a value of 0, the corresponding rate bit field indicates non-legacy WLAN information.

[0165] If it is determined that the Rate bit field contains non-legacy WLAN information, BSS identifier information is extracted from the three bit values preceding the corresponding Rate bit field, as illustrated in FIG. 18. However, the present invention is not limited to this. Non-legacy WLAN information, such as bandwidth information, channel information, and association identifier (AID) of the non-legacy WLAN signal, may also be extracted from the Rate bit field. In this case, the actual Rate information for the non-legacy terminal is transmitted via the non-legacy preamble. Meanwhile, even if the Rate bit field contains non-legacy WLAN information, legacy terminals interpret it as Rate information. For this situation, by appropriately setting the length field of the L-SIG, legacy terminals can perform transmission delays (such as NAV setting) using the L-SIG length information of other terminal packets when a transmission delay is required for the transmission of other terminals. More specifically, since the length field of the legacy preamble indicates the size (number of bytes) of transmission data, information on the number of transmission bits per OFDM symbol is obtained based on the modulation and coding scheme (MCS) of the rate bit field, and the number of required OFDM symbols can be determined by dividing the length field using this. At this time, a network allocation vector (NAV) is set according to the obtained number of OFDM symbols, but when the rate bit field is used as non-legacy WLAN information according to an embodiment of the present invention, the length field may be adjusted to set the NAV to the required length.

[0166] According to an embodiment of the present invention, it is determined whether a legacy preamble includes non-legacy WLAN information based on information in a predetermined bit of the legacy preamble. If it is determined that the legacy preamble includes non-legacy WLAN information, non-legacy WLAN information such as BSS identifier information is extracted from a predetermined bit field, for example, a Rate bit field, of the legacy preamble.

[0167] Meanwhile, according to additional embodiments of the present invention, more bits can be identified by using a combination of the second subcarrier set and the specific bit field (e.g., the Rate bit field) of the legacy preamble, and non-legacy WLAN information can be transmitted through this. For example, if the legacy preamble additionally includes the second subcarrier set, the UE determines that the corresponding legacy preamble includes non-legacy WLAN information and extracts all four bits of the Rate bit field or BSS identifier information. Furthermore, if the legacy preamble additionally includes the second subcarrier set, the non-legacy UE may analyze the entire L-SIG bit field of the legacy preamble as non-legacy WLAN information. As such, according to the embodiment of FIG. 18, at least a portion of non-legacy WLAN information, such as BSS identifier information, can be obtained from the legacy preamble before identifying the non-legacy preamble, thereby shortening the time required for CCA.

[0168] 19 illustrates an inequality problem that may occur for legacy terminals when a CCA threshold adjusted according to an embodiment of the present invention is used for channel access. In FIG. 19 and the following embodiments, MT (MYBSS Transmitter) and MR (MYBSS Receiver) respectively refer to a transmitting terminal and a receiving terminal of a first BSS (MYBSS), and OT (OBSS Transmitter) and OR (OBSS Receiver) refer to a transmitting terminal and a receiving terminal of a different second BSS (OBSSS). It is also assumed that MT, MR, OT, and OR are non-legacy terminals, and L is a legacy terminal.

[0169] 19, in the OBSS, terminal OT transmits data (O_DATA) to terminal OR, and terminal OR transmits a response message (O_ACK) to terminal OT in response to the received data (O_DATA). At this time, if the received signal strength of the wireless signal O_DATA is higher than the first CCA threshold CCA-SD1, legacy terminal L located near terminals OT and OR determines that the channel is occupied and does not perform channel access. At this time, the channel access deferral period 810 of legacy terminal L is set to last until terminal OR completes transmission of the response message (O_ACK).

[0170] Meanwhile, the terminals MT of the OBSS and another BSS, MYBSS, determine whether to occupy a channel based on the received signal strength of the wireless signal O_DATA and the BSS identifier of the corresponding signal, as in the above-described embodiment. That is, if the BSS identifier of the received wireless signal O_DATA differs from the BSS identifier of the corresponding terminal, the terminal MT performs CCA based on the second CCA threshold CCA-SD2. In this case, the second CCA threshold CCA-SD2 has a higher level than the first CCA threshold CCA-SD1 used by legacy terminals. Therefore, assuming that O_DATA is received by the legacy terminal L and the non-legacy terminal MT with a received signal strength between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, respectively, the channel access of the legacy terminal L is postponed, but the channel access of the non-legacy terminal MT is permitted.

[0171] Thus, if the received signal strength of O_DATA is lower than the second CCA threshold CCA-SD2, the terminal MT determines the corresponding channel as idle and performs channel access. That is, the terminal MT performs a backoff procedure, and when the backoff counter of the backoff procedure expires, it transmits data (MY_DATA). In addition, the terminal MR, which receives MY_DATA from the terminal MT, transmits a response message (MY_ACK) in response. In this case, if the transmission of the wireless signals MY_DATA and MY_ACK exchanged between the terminals MT and MR is completed before the channel deferral period 810 set in the legacy terminal L, the legacy terminal L cannot access the channel even during the additional period 820 after the channel access deferral period 810. This problem can occur not only during terminal MPDU transmission, but also in transmission situations based on a transmission opportunity (TXOP) or an aggregate MPDU (A-MPDU).

[0172] 20 to 23 illustrate a data transmission method for a non-legacy terminal to solve the channel access delay problem of a legacy terminal.

[0173] 20 is a diagram illustrating a frame structure of a non-legacy WLAN signal according to an embodiment of the present invention. Referring to FIG. 20, the non-legacy WLAN signal includes a preamble 910, an L-SIG field 920 for legacy terminals (e.g., 802.11a / g terminals), a HEW-SIG field 930 for non-legacy terminals (e.g., 802.11ax terminals), and a MAC header field 940. In this embodiment, the L-SIG field 920 indicates at least a portion of the legacy preamble, and the HEW-SIG field 930 indicates at least a portion of the non-legacy preamble. According to this embodiment, the L-SIG field 920, the HEW-SIG field 930, and the MAC header 940 each include length information indicating the length of data transmission. In the present invention, the length information included in the L-SIG 920 is referred to as LEN-1, the length information included in the HEW-SIG 930 is referred to as LEN-2, and the length information included in the MAC header 940 is referred to as LEN-3. According to an embodiment of the present invention, LEN-1 refers to the length field of the L-SIG field 920, LEN-2 refers to the length field of the HEW-SIG field 930, and LEN-3 refers to the duration field of the MAC header 940, but the present invention is not limited thereto.

[0174] According to an embodiment of the present invention, LEN-1 indicates the length of the corresponding frame. Here, the frame length information may be expressed as time information required for frame transmission, or may be expressed as data size (number of bytes) information that can be combined with other information to estimate the time required for transmission. Meanwhile, LEN-2 indicates the length information until the transmission of the corresponding frame and all related frames is completed. Here, related frames include subsequent frames of the corresponding frame. According to another embodiment of the present invention, LEN-2 indicates the length information until the transmission of the corresponding frame and all related frames is completed and before other contention windows are activated. Here, related frames include not only subsequent frames of the corresponding frame but also ACK frames corresponding to each transmitted frame. Thus, the length information indicated by LEN-2 is referred to as "total transmission length information" in this embodiment of the present invention. According to one embodiment, LEN-2 may indicate information in the duration field of the corresponding frame or the length information of the TXOP granted to the terminal transmitting the corresponding frame. Finally, LEN-3 indicates arbitrary length information defined by MAC.

[0175] Meanwhile, the information indicated by LEN-1 and LEN-2 is not limited to the above and may be modified in other ways. That is, in an embodiment of the present invention, at least one of LEN-1 and LEN-2 indicates total transmission length information. If LEN-1 indicates length information (e.g., total transmission length information) that exceeds the length of the corresponding frame, the corresponding frame additionally includes LLE (L-SIG Length Extend) information indicating this. Similarly, if LEN-2 indicates length information (e.g., total transmission length information) that exceeds the length of the corresponding frame, the corresponding frame additionally includes HLE (HEW-SIG Length Extend) information indicating this.

[0176] When a terminal with data to transmit receives non-legacy WLAN information (i.e., a non-legacy WLAN signal of another BSS) having BSS identifier information different from that of the terminal, the terminal performs channel access based on the CCA procedure according to the above-described embodiment. In this case, according to an embodiment of the present invention, the terminal adjusts the data transmission period of the terminal using at least one of information LEN-1, LEN-2, and LEN-3 of the received non-legacy WLAN signal of the other BSS. If the terminal transmits a single frame, the data transmission period refers to the duration of the frame. If the terminal transmits multiple frames consecutively, the data transmission period refers to the TXOP of the terminal. A specific embodiment of this will be described with reference to Figures 21 to 23.

[0177] First, Figure 21 illustrates an embodiment for adjusting a terminal's data transmission period based on length information of a received WLAN signal. Referring to Figure 21, terminal OT of an OBSS transmits data (O_DATA) to terminal OR, and terminal OR transmits a response message (O_ACK) to terminal OT in response to the received data (O_DATA). If terminal MT transmits data (MY_DATA) while O_DATA is being transmitted, terminal MT extracts length information LEN(O_DATA) from the received wireless signal O_DATA and adjusts the transmission period of the data (MY_DATA) based on the extracted length information LEN(O_DATA). In this case, the extracted length information LEN(O_DATA) includes at least one of LEN-1, LEN-2, and LEN-3 extracted from O_DATA. In the embodiment of Figure 21, LEN-1 indicates the length information of O_DATA, and LEN-2 indicates the overall transmission length information of O_DATA+SIFS+O_ACK.

[0178] According to the embodiment of FIG. 21, the terminal MT adjusts the transmission period of the MY_DATA transmitted by the corresponding terminal based on the length information LEN_(O_DATA) extracted from the O_DATA so that the transmission period of the MY_DATA transmitted by the corresponding terminal is completed simultaneously with or before the completion of the transmission of the wireless signal O_DATA. That is, the terminal MT adjusts the length of the MY_DATA transmitted by the corresponding terminal to be equal to or less than LEN(O_DATA). The WLAN data MY_DATA of the terminal MT is transmitted in the form of a PPDU (PLCP Protocol Data Unit), and the terminal MT adjusts the length of the MY_DATA in various ways. For example, if the PPDU is configured as a terminal MPDU, the terminal MT performs fragmentation (framenation) on the corresponding MPDU based on the extracted length information to reduce the length of the MY_DATA. Also, if the PPDU is configured as an A-MPDU, the terminal MT reduces the length of the MY_DATA by limiting the number of MPDUs included in the A-MPDU or by fragmenting individual MPDUs based on the extracted length information. According to one embodiment, the terminal MT refers to the LLE information and / or HLE information of the O_DATA when adjusting the length of the MY_DATA.

[0179] 21, if the transmission period of MY_DATA ends simultaneously with the completion of transmission of O_DATA, the response message (MY_ACK) of terminal MR and the response message (O_ACK) of terminal OR are transmitted simultaneously. However, if MY_ACK and O_ACK are received simultaneously by legacy terminal L, legacy terminal L recognizes that a data collision 830 has occurred. Therefore, a problem occurs in which legacy terminal L approaches the channel after an Extended Inter Frame Spacing (EIFS), which is longer than an AIFS, after transmission of the response messages (MY_ACK, O_ACK) has ended.

[0180] Next, Fig. 22 shows another embodiment of adjusting the data transmission period of a terminal based on the length information of a received WLAN signal. In the embodiment of Fig. 22, the same or corresponding parts as those in the embodiment of Fig. 21 will not be described again.

[0181] According to the embodiment of FIG. 22, the terminal MT adjusts the transmission period of the MY_DATA transmitted by the corresponding terminal based on the length information LEN(O_DATA) extracted from the O_DATA so that it ends before the completion of the transmission of the radio signal O_DATA. That is, the terminal MT adjusts the length of the MY_DATA transmitted by the corresponding terminal to be less than LEN(O_DATA). More specifically, referring to FIG. 22, the terminal MT sets the length of the MY_DATA to be equal to or less than LEN(O_DATA)-LEN(MY_ACK)-SIFS. Here, LEN(MY_ACK) indicates the length of the MY_ACK. That is, the terminal MT sets the transmission period of the MY_DATA so that it ends at least one SIFS time and the time required for transmitting the response message (MY_ACK) before the completion of the transmission of the O_DATA. Therefore, in the embodiment of FIG. 22, the transmission of the MY_DATA and the corresponding MY_ACK ends within the transmission period of the O_DATA.

[0182] Meanwhile, terminal MT, terminal MR, or other terminals in MY BSS may attempt data transmission while O_ACK is being transmitted. According to one embodiment, arbitrary information may be inserted into a predetermined specific message, such as an RTS, CTS, or ACK message, and if a message including the corresponding information is received, the adjustment of the CCA threshold according to the above embodiment may not be permitted. That is, terminals in other BSSs that receive the message perform channel access based on the first CCA threshold CCA-SD1 rather than the second CCA threshold CCA-SD2.

[0183] 22, all terminals, including legacy terminals, attempt channel access if the channel is idle during the AIFS period after the O_ACK transmission of the terminal OR is completed, thereby ensuring fair access opportunities between non-legacy terminals and legacy terminals.

[0184] 23 is a diagram illustrating another embodiment of adjusting the data transmission period of a terminal based on the length information of a received WLAN signal. In the embodiment of FIG. 23, the same or corresponding parts as those in the above-described embodiments of FIG. 21 and FIG. 22 will not be described again.

[0185] According to the embodiment of Figure 23, a terminal OT of an OBSS continuously transmits a plurality of data (O_DATA-1, O_DATA-2, O_DATA-3) during a TXOP interval (OT_TXOP) allocated to the terminal. In the case of a Quality of Service (QoS) terminal transmitting video data, voice data, etc., a plurality of data including at least one subsequent frame is continuously transmitted during a TXOP interval allocated to the terminal. In addition, a terminal OR receiving a plurality of data from the terminal OT transmits response messages (O_ACK-1, O_ACK-2, O_ACK-3) corresponding to each received frame. The transmission of the plurality of data and the corresponding response messages is completed within a TXOP interval (OT_TXOP) allocated to the terminal OT.

[0186] In this way, when the terminal MT transmits data while the terminal OT transmits a plurality of data, the terminal MT extracts length information from at least one of the plurality of data (O_DATA-1, O_DATA-2, O_DATA-3) and adjusts the data transmission period of the corresponding terminal based on the extracted information. In this case, the terminal MT extracts length information from the data of the terminal OT received in the process of performing CCA to transmit the data of the corresponding terminal. If the terminal MT transmits terminal data, the data transmission period means the duration of the corresponding data frame, and if the terminal MT transmits a plurality of data continuously, the data transmission period means the TXOP of the corresponding terminal.

[0187] 23, when terminal MT transmits data during transmission of O_DATA-1, terminal MT extracts length information LEN(O_DATA-1) from O_DATA-1 and adjusts the data transmission period of the terminal MT based on the extracted length information LEN(O_DATA-1). In this case, the extracted length information LEN(O_DATA-1) includes at least one of LEN-1, LEN-2, and LEN-3 extracted from O_DATA-1. In the embodiment of FIG. 23, LEN-1 indicates the length of the data O_DATA-1 from which the corresponding length information was extracted, and LEN-2 indicates the length of the TXOP interval (OT_TXOP) allocated to terminal OT transmitting the corresponding data O_DATA-1, i.e., (O_DATA-1 + SIFS + O_ACK-1) + SIFS + (O_DATA-2 + SIFS + O_ACK-2) + SIFS + ... + SIFS + (O_DATA-n + SIFS + O_ACK-n). Also, LEN-3 indicates an arbitrary length defined by MAC.

[0188] As described above, the information indicated by LEN-1 and LEN-2 is not limited to this and may be modified in other ways. For example, LEN-1 may indicate the length of the TXOP interval (OT_TXOP) allocated to the terminal OT transmitting the corresponding data O_DATA-1. If LEN-1 indicates length information (e.g., total transmission length information) that exceeds the length of the corresponding data O_DATA-1, O_DATA-1 additionally includes LLE information indicating this. Similarly, if LEN-2 indicates length information (e.g., total transmission length information) that exceeds the length of the corresponding data O_DATA-1, O_DATA-1 additionally includes HLE information indicating this.

[0189] According to the embodiment of Figure 23, the terminal MT adjusts the data transmission period of the terminal MT based on the extracted length information LEN(O_DATA-1) so that it ends before the data transmission completion point of the terminal OT. As in the embodiment of Figure 23, when the terminal transmits multiple pieces of data continuously, the length of the TXOP interval (MT_TXOP) allocated to the terminal MT, i.e., (MY_DATA-1 + SIFS + MY_ACK-1) + SIFS + (MY_DATA-2 + SIFS + MY_ACK-2) + SIFS + ... + SIFS + (MY_DATA-m + SIFS + MY_ACK-m), is set to be shorter than the length of the TXOP interval (OT_TXOP) allocated to the terminal OT. More specifically, referring to Figure 23, the length of the TXOP interval (MT_TXOP) allocated to the terminal MT is set to be equal to or shorter than OT_TXOP-LEN(O-ACK)-SIFS. That is, the terminal MT adjusts the total length of one or more data transmitted by the terminal so that it is equal to or less than LEN-2(O_DATA-1)-LEN(O_ACK-n)-LEN(MY_ACK-m)-SIFS. Here, it is assumed that the OT_TXOP information is extracted from LEN-2 of O_DATA-1, and LEN-2(O_DATA-1) indicates the extracted LEN-2 information. Also, LEN(O_ACK-n) indicates the length of the response message for the last transmission data (O_DATA-n) of the terminal OT, and LEN(MY_ACK-m) indicates the length of the response message for the last transmission data (MY_DATA-m) of the terminal MT.

[0190] Therefore, in the embodiment of Figure 23, the transmission of one or more data (MY_DATA-1, MY_DATA-2) and the corresponding response messages (MY_ACK-1, MY_ACK-2) transmitted by terminal MT is completed within the TXOP period (OT_TXOP) assigned to terminal OT. All terminals, including legacy terminals, attempt channel access if the channel is idle during the AIFS time after the transmission of the last response message (O_ACK-n) of terminal OR is completed. Therefore, fair channel access opportunities are guaranteed between non-legacy terminals and legacy terminals.

[0191] According to an embodiment of the present invention, the terminal MT determines the data transmission period of the corresponding terminal by using length information (LEN-1 or LEN-2) extracted from the L-SIG field or HEW-SIG field of the received wireless signal O_DATA. In this case, the terminal MT adjusts the transmission period of the corresponding terminal to a faster time before decoding the MAC header of O_DATA.

[0192] 24 illustrates yet another embodiment for solving the inequality problem of legacy terminals that may occur when a CCA threshold adjusted according to an embodiment of the present invention is used for channel access. In the embodiment of FIG. 24, HE, HE0, HE1, HE2, HE3, HE4, HE A, and HE B respectively represent non-legacy terminals, and Leg and Leg X respectively represent legacy terminals. Also, terminals HE1, HE2, HE3, and Leg X are connected to a first BSS operated by HE A, and terminals HE, HE0, and Leg are connected to a second BSS operated by HE B.

[0193] In the embodiment of Figure 24, when terminal HE0 in BSS2 transmits data, the corresponding data signal is detected by terminals in neighboring BSS1. When wireless signals from other BSSs are detected in this manner, non-legacy terminals HE1, HE2, and HE3 in BSS1 perform CCA based on the second CCA threshold CCA-SD2, and legacy terminal Leg X performs CCA based on the first CCA threshold CCA-SD1. If it is assumed that data from terminal HE0 is received by each terminal with a received signal strength between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, non-legacy terminals HE1, HE2, and HE3 perform a backoff procedure by decrementing their assigned backoff counters (backoff1, backoff2, and backoff3), but legacy terminal Leg X cannot perform a backoff procedure and defers channel access, resulting in an inequality problem.

[0194] Furthermore, when UEs HE0 and HE1 complete their data transmission and the channel becomes idle, non-legacy UEs HE2 and HE3 resume the backoff procedure using the remaining backoff counters (remaining backoff2 and remaining backoff3) from the previous backoff procedure. However, since UE Leg X was unable to decrease its backoff counter during the non-legacy UE's previous backoff procedure, it resumes the backoff procedure using the backoff counter (backoff X) previously assigned to the UE. Therefore, even in the subsequent contention window, legacy UEs are less likely to access the channel than non-legacy UEs.

[0195] To solve this problem, according to an embodiment of the present invention, a backoff counter used in a backoff procedure of a non-legacy UE in a spatial reuse interval is adjusted to maintain fairness in channel access between the non-legacy UE and the legacy UE. The spatial reuse interval in the present invention refers to an interval in which channel access is performed based on an adjusted CCA threshold when the BSS identifier information of a received wireless signal is different from the BSS identifier information of the UE.

[0196] In the spatial reuse domain, non-legacy terminals HE1, HE2, and HE3 of the first BSS perform CCA based on the second CCA threshold CCA-SD2. If the CCA determines that the corresponding channel is idle, the non-legacy terminals perform a backoff procedure using the backoff counters assigned to each terminal. In the embodiment of Figure 24, during the backoff procedure, terminal HE1, whose backoff counter expires first, transmits data. At this time, the backoff procedures of the remaining terminals HE2 and HE3 are suspended.

[0197] In this way, if the backoff procedure is interrupted, the non-legacy terminal adjusts the backoff counter assigned to the terminal and resumes the backoff procedure using the adjusted backoff counter when the corresponding channel becomes idle again. According to one embodiment, the non-legacy terminal restores the backoff counter that was decremented during the backoff procedure in the spatial reuse space to the value before backoff. According to another embodiment, the non-legacy terminal is assigned a new backoff counter when the backoff procedure is interrupted in the spatial reuse space. This backoff counter adjustment is performed when the received signal strength of a wireless signal having BSS identifier information different from that of the terminal is between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2.

[0198] Meanwhile, according to another embodiment of the present invention, a non-legacy terminal performs channel access using multiple backoff counters. For example, the non-legacy terminal is assigned a first backoff counter and a second backoff counter for the backoff procedure. In this case, the non-legacy terminal performs the backoff procedure using at least one of the first backoff counter and the second backoff counter based on the received signal strength of the received wireless signal. For example, the non-legacy terminal depletes the backoff counter if the received signal strength of a wireless signal having BSS identifier information different from that of the corresponding terminal is lower than the first CCA threshold CCA-SD1, and depletes the second backoff counter if the received signal strength of the wireless signal is between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2. The non-legacy terminal transmits data when at least one of the first backoff counter and the second backoff counter expires.

[0199] In this way, non-legacy terminals according to the embodiment of FIG. 24 can minimize inequality that may occur in legacy terminals by adjusting the backoff counters used in the backoff procedure in the spatial reuse interval or by performing the backoff procedure using multiple backoff counters.

[0200] 25 is a diagram illustrating an interference problem that may occur when a CCA threshold adjusted according to an embodiment of the present invention is used for channel access. In FIG. 25 and the following embodiments, MT and MR respectively represent a transmitting terminal and a receiving terminal of a first BSS (MYBSS), and OT and OR represent a transmitting terminal and a receiving terminal of a second BSS (OBSSS) different from the first BSS.

[0201] As shown in Figure 25, in the OBSS, the terminal OT transmits data (O_DATA) to the terminal OR, and the terminal OR transmits a response message (O_ACK) to the terminal OT in response to the received data (O_DATA). Meanwhile, the terminal MT of the BSS MY BSS, which is different from the OBSS, determines whether to occupy the channel based on the received signal strength of the wireless signal O_DATA and the BSS identifier information of the corresponding signal, as in the above-mentioned embodiment. That is, if the BSS identifier information of the received wireless signal O_DATA differs from the BSS identifier information of the corresponding terminal, the terminal MT performs CCA based on the above-mentioned second CCA threshold CCA-SD2. In this case, the second CCA threshold has a higher level than the first CCA threshold used in legacy terminals.

[0202] If the received signal strength of O_DATA is lower than the second CCA threshold, the terminal MT determines that the channel is idle and performs channel access. That is, the terminal MT performs a backoff procedure, and when the backoff counter of the backoff procedure expires, it transmits data MY_DATA. In addition, the terminal MR, which has received MY_DATA from the terminal MT, transmits a response message (MY_ACK) in response.

[0203] However, since the channel accessibility of terminal MT is determined based on the received signal strength of O_DATA transmitted by terminal OT, MY_DATA transmitted by terminal MT causes interference to terminal OR of OBSS. This problem can occur not only in single MPDU transmission but also in TXOP-based or A-MPDU-based transmission situations.

[0204] 26 and 27 illustrate a data transmission method for non-legacy terminals to minimize interference between terminals. In the embodiments of Figures 26 and 27, terminal OT of OBSS may transmit one or more data (O_DATA-1, O_DATA-2) to terminal OR, which will be referred to as O_DATA. Also, terminal MT of MYBSS may transmit one or more data (MY_DATA-1, MY_DATA-2) to terminal MR, which will be referred to as MY_DATA.

[0205] First, Figure 26 shows an embodiment for minimizing interference caused by a terminal MT in a MYBSS to an OBS terminal OR. Referring to Figure 26, terminals communicating via a wireless LAN exchange a request (REQ) message and a response (RSP) message before transmitting data. In this embodiment, the request message / response message respectively indicate RTS / CTS, NPD (Null Data Packet) / ACK, or terminal MPDU / ACK. In the embodiment of Figure 26, it is assumed that a request message (O_REQ) transmitted by a terminal OT in an OBS and a response message (O_RSP) transmitted by a terminal OR are received by a terminal MT in a MYBSS.

[0206] According to an embodiment of the present invention, when a terminal MT of a MYBSS receives a request message (O_REQ) and a corresponding response message (O_RSP) having BSS identifier information different from that of the corresponding terminal, the terminal MT determines whether to allow channel access, i.e., whether to transmit data (MY_DATA) of the corresponding terminal, based on the received signal strength of the O_REQ and O_RSP. In this case, the terminal MT determines whether to transmit MY_DATA based on the result of comparing the received signal strength of the O_REQ and O_RSP with the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2. Here, the second CCA threshold CCA-SD2 has a higher level than the first CCA threshold CCA-SD1.

[0207] First, if the received signal strength of at least one of O_REQ or O_RSP is higher than the second CCA threshold CCA-SD2, the terminal MT waits for the transmission of MY_DATA. Also, even if the received signal strengths of O_REQ and O_RSP are both between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, the terminal MT waits for the transmission of MY_DATA. However, in this case, the terminal MT may exceptionally transmit data based on additional information such as the importance of the data to be transmitted. On the other hand, if the received signal strengths of O_REQ and O_RSP are all lower than the first CCA threshold CCA-SD1, the terminal MT approaches the channel and transmits MY_DATA.

[0208] Next, if the received signal strength of O_REQ is between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2 and the received signal strength of O_RSP is lower than the first CCA threshold CCA-SD1, the terminal MT approaches the channel and transmits MY_DATA. Therefore, when the received signal strength of O_REQ is lower than the second CCA threshold CCA-SD2 and the received signal strength of O_RSP is lower than the first CCA threshold CCA-SD1, the terminal MT approaches the channel and transmits MY_DATA. In this case, it is estimated that the interference effect of MY_DATA transmitted by the terminal MT on the terminal OR is small. Therefore, the terminal OR successfully receives the data (O_DATA-1, O_DATA-2) transmitted by the terminal OT. In this way, when the BSS identifier information of the received wireless signal is different from the BSS identifier information of the terminal, the interval in which channel access is performed based on the adjusted CCA threshold is referred to as a spatial reuse interval in the present invention.

[0209] According to one embodiment of the present invention, a terminal MT transmitting data in the spatial reuse space can immediately transmit data without exchanging separate request and response messages. Furthermore, the terminal MT continuously measures the received signal strength of data transmitted by OBSS terminals in the spatial reuse space and adjusts channel accessibility in real time based on the measurement results. The same criteria as for O_REQ are applied to data (O_DATA-1, O_DATA-2) transmitted by OBSS terminal OT, and the same criteria as for O_RSP are applied to data (O_ACK-1, O_ACK-2) transmitted by terminal OR. If the received signal strength of data transmitted by the OBSS terminal falls within the same signal strength interval as the received signal strength of the corresponding O_REQ or O_RSP, the terminal MT continues to operate based on the predetermined channel accessibility. However, if the received signal strength of data transmitted by the OBSS terminal falls within a different signal strength interval from the received signal strength of the corresponding O_REQ or O_RSP, the terminal MT re-determines channel accessibility based on the received signal strength of the received data. Here, the received signal strength section includes a first section lower than the first CCA threshold CCA-SD1, a second section between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, and a third section higher than the second CCA threshold CCA-SD2.

[0210] If O_REQ and O_RSP contain the length information according to the above embodiment, the terminal MT that receives them extracts the length information from the corresponding message and adjusts the data transmission period of the corresponding terminal MT based on the extracted length information. In this case, the terminal MT omits the operation of extracting the length information from the data (O_DATA-1, O_DATA-2) transmitted by the terminal OT.

[0211] Next, Figure 27 shows an additional embodiment for minimizing interference of MYBSS with the terminal MR. In the embodiment of Figure 27, duplicated descriptions of parts that are the same as or correspond to the embodiment of Figure 26 described above will be omitted.

[0212] As described above in the embodiment of Figure 26, when the terminal of the OBSS transmits O_REQ and O_RSP, the terminals MT and MR of the MYBSS receive them. The terminal MT of the MYBSS determines whether to access the channel based on the received signal strength of O_REQ and O_RSP. According to the embodiment of Figure 27, if it is determined that the terminal MT will access the channel, the terminal MT transmits a request message (MY_REQ) to the receiving terminal MR. The MY_REQ is a message indicating that the terminal MT is able to transmit data, and is embodied as an RTS, NDP, or a single MPDU.

[0213] The terminal MR, which has received MY_REQ from the terminal MT, determines whether to receive data (MY_DATA) of the terminal MT based on the received signal strength of O_REQ and O_RSP. At this time, the terminal MR determines whether to receive MY_DATA based on the result of comparing the received signal strength of O_REQ and O_RSP with the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2. Here, the second CCA threshold CCA-SD2 has a higher level than the first CCA threshold CCA-SD1.

[0214] First, if the received signal strength of at least one of O_REQ or O_RSP is higher than the second CCA threshold CCA-SD2, the terminal MR cannot receive MY_DATA. Also, even if the received signal strengths of O_REQ and O_RSP are all between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, the terminal MR cannot receive MY_DATA. However, in this case, the terminal MR may exceptionally receive data depending on other additional information, such as the importance of MY_DATA. On the other hand, if the received signal strengths of O_REQ and O_RSP are all lower than the first CCA threshold CCA-SD1, the terminal MR cannot receive MY_DATA.

[0215] Next, if the received signal strength of O_RSP is between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2 and the received signal strength of O_REQ is lower than the first CCA threshold CCA-SD1, the terminal MR can receive MY_DATA. Therefore, in a situation where the received signal strength of O_RSP is lower than the second CCA threshold CCA-SD2, the terminal MR can receive MY_DATA if the received signal strength of O_REQ is lower than the first CCA threshold CCA-SD1. In this case, it is estimated that the interference effect of O_DATA transmitted by the terminal OT of the OBSS on the MR is small. Therefore, the terminal MR can successfully receive the data (MY_DATA-1, MY_DATA-2) transmitted by the terminal MT.

[0216] The terminal MR transmits a response message (MY_RSP) corresponding to the MY_REQ transmitted by the terminal MT based on the determined reception status of MY_DATA. The MY_RSP is a message indicating that the terminal MT can receive data, and is embodied as a CTS or an ACK. If the terminal MR can receive MY_DATA, the terminal MR transmits the MY_RSP corresponding to the MY_REQ to the terminal MT. When the terminal MT receives the MY_RSP from the terminal MR, the terminal MT starts transmitting MY_DATA. However, if the terminal MR cannot receive MY_DATA, the terminal MR does not transmit the MY_RSP. If the terminal MR does not receive the MY_RSP from the terminal MR, the terminal MT cannot transmit the MY_DATA. As described above, according to the embodiment of FIG. 27, the terminals of the MYBSS exchange MY_REQ and MY_RSP in the spatial reuse period, thereby additionally determining whether the terminal MR can receive the data (MY_DATA) of the terminal MT without interference.

[0217] 28 and 29 are diagrams illustrating another interference problem that may occur when the CCA threshold adjusted according to an embodiment of the present invention is used for channel access. In the embodiments of FIG. 28 and FIG. 29, the same or corresponding parts as the embodiment of FIG. 25 will not be described again.

[0218] As shown in Figures 28 and 29, in the OBSS, the terminal OT transmits data (O_DATA) to the terminal OR, and the terminal OR transmits a response message (O_ACK) to the terminal OT in response to the received data (O_DATA). Meanwhile, the terminal MT of the BSS MYBSS, which is different from the OBSS, determines whether the channel is occupied according to the above-mentioned embodiment and performs channel access. That is, the terminal MT performs a backoff procedure, and transmits data (MY_DATA) when the backoff counter of the backoff procedure expires. In addition, the terminal MR, which receives MY_DATA from the terminal MT, transmits a response message (MY_ACK) in response to this.

[0219] However, the MY_ACK transmitted by the terminal MR may cause interference to the terminals of the OBSS. Referring to Figure 28, the MY_ACK transmitted by the terminal MR may interfere with the terminal OR receiving data (O_DATA) from the terminal OT. Also, referring to Figure 29, the MY_ACK transmitted by the terminal MR may interfere with the terminal OT receiving a response message (O_ACK) from the terminal OR.

[0220] 30 is a diagram illustrating yet another embodiment of a method for transmitting data from a non-legacy terminal to minimize interference between terminals. In the embodiment of FIG. 30, duplicated descriptions of parts that are the same as or correspond to the embodiments of FIG. 26 and FIG. 27 will be omitted.

[0221] As shown in the figure, when a terminal in the OBSS transmits O_REQ and O_RSP, the terminals MT and MR in the MYBSS can receive them. As in the above-described embodiment, the terminal MT in the MYBSS determines whether to access the channel based on the received signal strength of the O_REQ and O_RSP and transmits data (MY_DATA). Furthermore, the terminal MR that receives MY_DATA transmits a corresponding response message (MY_ACK). According to an embodiment of the present invention, the terminal MR determines the transmission time of MY_ACK based on the received signal strength of the O_REQ and O_RSP. In this case, the terminal MR determines the transmission time of MY_ACK based on the result of comparing the received signal strength of the O_REQ and O_RSP with the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2. Here, the second CCA threshold CCA-SD2 has a higher level than the first CCA threshold CCA-SD1.

[0222] First, if the received signal strength of O_REQ is between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, and the received signal strength of O_RSP is lower than the first CCA threshold CCA-SD1, the terminal MR transmits MY_ACK 841 within the transmission period of the data (O_DATA) of the terminal OT. In this case, it is estimated that the interference effect of MY_ACK 841 transmitted by the terminal MR on the OBSS terminal OR is small. Therefore, the terminal OR can successfully receive the O_DATA transmitted by the terminal OT.

[0223] Next, if the received signal strength of O_RSP is between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, and the received signal strength of O_REQ is lower than the first CCA threshold CCA-SD1, the terminal MR transmits MY_ACK 842 along with the terminal OR response message (O_ACK). In this case, it is estimated that the MY_ACK 842 transmitted by the terminal MR will have little impact on the OBSS terminal OT. Therefore, the terminal OT can successfully receive the O_ACK transmitted by the terminal OR.

[0224] Next, if the received signal strengths of O_REQ and O_RSP are both higher than the second CCA threshold CCA-SD2, the terminal MR transmits MY_ACK 843 after completing the transmission of the terminal OT data (O_DATA) and the terminal OR's response message (O_ACK). In this case, it is estimated that MY_ACK 843 transmitted by the terminal MR will interfere with the OBSS terminals OT and OR. Therefore, by transmitting MY_ACK 843 after the data exchange between the terminals OT and OR is completed, the terminal MR can prevent data collisions that may occur in the OBSS terminals.

[0225] According to a further embodiment of the present invention, the terminal MR can adjust the transmission power of MY_ACK in consideration of the transmission power of the corresponding terminal and the received signal strength of MY_DATA, etc. Through this, the terminal MR can minimize the amount of interference that MY_ACK causes to the terminal OT and the terminal OR.

[0226] Although the present invention has been described above using wireless LAN communication as an example, the present invention is not limited thereto and can be equally applied to other communication systems such as cellular communication. Also, although the method, apparatus, and system of the present invention have been described in connection with specific embodiments, some or all of the components and operations of the present invention may be implemented using a computer system having a general-purpose hardware architecture.

[0227] The above-described embodiments of the present invention may be implemented in various ways, for example, in hardware, firmware, software, or a combination thereof.

[0228] In the case of a hardware implementation, the method according to an embodiment of the present invention may be implemented by one or more AICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), DSPDs (Digital Signal Processing Devices), PLDs (Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays), processors, controllers, microcontrollers, microprocessors, etc.

[0229] In the case of implementation by firmware or software, the methods according to the embodiments of the present invention may be implemented in the form of modules, procedures, or functions that perform the functions or operations described above. The software code is stored in memory and processed by the processor. The memory may be located inside or outside the processor and exchange data with the processor by various means known in the art.

[0230] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention may be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. Therefore, the above-described embodiments should be considered to be illustrative and restrictive in all respects. For example, each component described as a single component may be implemented in a distributed form, and each component described as a distributed component may be implemented in a combined form.

[0231] The scope of the present invention is indicated by the claims below rather than the above detailed description, and all modifications and variations derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention. [Industrial Applicability]

[0232] Although various embodiments of the present invention have been described with a focus on the IEEE 802.11 system, they may be applied to various other types of mobile communication devices, mobile communication systems, and the like.

Claims

[Claim 1] A wireless communication terminal, a transceiver configured to transmit and receive wireless signals; a processor configured to process wireless signals transmitted and received via the transceiver; The processor: receiving, via the transceiver unit, a first packet including basic service set (BSS) identifier information; transmitting a second packet based on the first packet; Wireless communication terminal.

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