Wireless communication method for simultaneous communication of data 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. More specifically, the present invention relates 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 Art

[0002] Recently, with the spread of mobile devices, wireless LAN (Local Area Network) technology that provides fast wireless Internet services for these devices has been in the spotlight. Wireless LAN technology is a technology that enables mobile devices such as smartphones, smart pads, laptop computers, portable multimedia players, and embedded devices to be wirelessly connected to the Internet at home, in enterprises, or in specific service-providing areas based on wireless communication technology at short distances.

[0003] Since IEEE (Institute of Electrical and Electronics Engineers) 802.11 supported the initial wireless LAN technology using a frequency of 2.4 GHz, various technology standards have been put into practical use or are under development. First, IEEE 802.11b supports a communication speed of up to 11 Mbps while using the frequency of the 2.4 GHz band. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses a frequency of the 5 GHz band instead of the 2.4 GHz band, thus reducing the impact on interference compared to the rather congested 2.4 GHz band frequency, and uses OFDM technology to improve the communication speed up to a maximum of 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication distance compared to IEEE 802.11b. And IEEE 802.11g uses the frequency of the 2.4 GHz band like IEEE 802.11b to achieve a communication speed of up to 54 Mbps and has received considerable attention for satisfying backward compatibility, but it is also superior to IEEE 802.11a in terms of communication distance.

[0004] And, as a technical standard established to overcome the limitations on communication speed that have been pointed out as vulnerabilities in wireless LANs, there is IEEE 802.11n. The purpose of IEEE 802.11n is to increase the speed and reliability of the network and expand the operating distance of the wireless network. More specifically, IEEE 802.11n supports a high processing rate (High Throughput, HT) with a maximum data processing speed of 540 Mbps or more, and is based on the MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas at both the transmitting and receiving ends to minimize transmission errors and optimize the data speed. Also, this standard uses a coding method that transmits multiple copies of data to increase the reliability of the data.

[0005] As the popularity of wireless LANs has been activated and the applications using them have diversified, there has been an emerging need for a new wireless LAN system that supports a processing rate (Very High Throughput, VHT) higher than the data processing speed that supports IEEE 802.11n. Among these, IEEE 802.11ac supports a wide bandwidth (80 MHz to 160 MHz) at 5 GHz frequency. The IEEE 802.11ac standard was only defined in the 5 GHz band, but for backward compatibility with conventional 2.4 GHz band products, the initial 11ac chipset also supports operation in the 2.4 GHz band. Theoretically, according to this standard, the speed of a wireless LAN with multiple stations can be up to a minimum of 1 Gbps, and the speed of a single link can be up to a minimum of 500 Mbps. This is achieved by expanding the wireless interface concepts adopted in 801.11n, such as a wider wireless frequency bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256QAM). Also, as a method of transmitting data using the 60 GHz band instead of the conventional 2.4 GHz / 5 GHz, there is IEEE 802.11ad. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide a speed of up to 7 Gbps and is suitable for streaming high-bitrate videos such as large-capacity data and uncompressed HD videos. However, the 60 GHz frequency band has the disadvantage that it is difficult for obstacles to pass through and can only be used between devices in a short-distance space.

[0006] On the other hand, recently, as a next-generation wireless LAN standard after 801.11ac and 802.11ad, discussions are being held to provide communication technologies for high-efficiency and high-performance wireless LANs in high-density environments. That is, in the next-generation wireless LAN environment, high-frequency efficiency communication should be provided indoors and outdoors in the presence of a high density of stations and APs (Access Points), and various technologies are required to implement this.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention aims to provide high-efficiency and high-performance wireless LAN communication in a high-density environment as described above.

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

[0009] Moreover, the present invention aims to increase the data transmission opportunity and transmission rate by providing an efficient spatial reuse method in an overlapping BSS environment.

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

[0011] Moreover, the present invention aims to minimize the interference problem between terminals in a spatial reuse interval.

Means for Solving the Problems

[0012] To solve the above problems, the present invention provides a wireless communication method and a wireless communication terminal as follows.

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

[0014] At this time, the determining step is performed based on CCA (Clear Channel Assessment) for the specific channel, and the CCA threshold values used for the CCA are 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] Also, if the BSS identifier information of the wireless signal is the same as the BSS identifier information of the terminal, the first CCA threshold is used for the CCA. If the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal, a second CCA threshold at a level higher than the first CCA threshold is used for the CCA.

[0016] Also, the method further includes a step of obtaining at least one of legacy wireless LAN information and non-legacy wireless LAN information by using the preamble information of the received wireless signal. In the determining step, if the non-legacy wireless LAN information is obtained from the wireless signal, it is determined whether the specific channel is occupied based on the BSS identifier information of the wireless signal.

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

[0018] At this time, the BSS identifier information indicates the reduced information of the BSS identifier for the wireless signal.

[0019] According to an embodiment of the present invention, in the determining step, it is determined whether the specific channel is occupied based on the comparison result between the BSS identifier information of the wireless signal and the BSS identifier information of the terminal.

[0020] At this time, in the determining step, when the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal, it is determined that the specific channel is in an idle state.

[0021] Further, in the determining step, when the BSS identifier information of the wireless signal is the same as the BSS identifier information of the terminal, it is determined that the specific channel is in a busy state.

[0022] According to an 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 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 sub-carrier set for the legacy terminal. When the first preamble further includes a second sub-carrier set different from the first sub-carrier set, the non-legacy wireless LAN information is obtained from the second sub-carrier set.

[0024] At this time, the BSS identifier information of the received wireless signal is extracted from the information of the second sub-carrier 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 based on a preset bit field of the first preamble, it is determined whether the wireless signal includes the non-legacy wireless LAN information.

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

[0027] At this time, the preset bit of the preset bit field indicates whether the wireless signal includes non-legacy wireless LAN information. When the preset bit indicates that the wireless signal includes non-legacy wireless LAN information, the 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 sub-carrier set for the legacy terminal. When the first preamble is further configured to include a second sub-carrier set different from the first sub-carrier set, the 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, including steps of receiving a wireless signal on a specific channel, extracting BSS identifier information of the received wireless signal, extracting length information from the wireless signal when the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal, where the length information indicates information related to a time point when transmission of the wireless signal is completed, 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 in a duration field of the wireless signal frame.

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

[0032] At this time, the length information is obtained from at least one of the legacy preamble, non-legacy preamble, and 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 completion time of the transmission of the wireless signal based on the extracted length information.

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

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

[0036] According to an additional embodiment of the present invention, it further includes a step of measuring the signal strength of the wireless signal, and a step of determining whether the specific channel is available 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] Also, the determining step is performed based on 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] At this time, if the BSS identifier information of the wireless signal is the same as the BSS identifier information of the terminal, a first CCA threshold value 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 value at a level higher than the first CCA threshold value is used for the CCA.

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

[0040] At this time, the backoff counter assigned to the terminal is adjusted when the received signal strength of the wireless signal performing 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 a value before the backoff procedure.

[0042] According to another embodiment, the adjusting step assigns a new backoff counter for the terminal.

[0043] Next, the present invention is a wireless communication method for a terminal, comprising steps of: allocating a first backoff counter and a second backoff counter for the backoff procedure of the terminal; receiving a wireless signal having other BSS identifier information different from the terminal; performing a backoff procedure based on the received signal strength of the wireless signal; wherein the backoff procedure includes 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 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 allocated within different random number ranges from each other.

[0045] Next, the present invention is a wireless communication method for a terminal, comprising steps of: receiving a request message (other BSS request message) having BSS identifier information different from the terminal; receiving a response message (other BSS response message) corresponding to the other BSS request message; and determining whether the terminal can access the channel based on the received signal strength of the other BSS request message and the 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, channel access of the terminal is permitted, wherein the second CCA threshold is set at a higher level than the first CCA threshold.

[0047] According to an additional embodiment of the present invention, when it is determined that the terminal approaches the channel, a request message (same BSS request message) indicating that data transmission of the terminal is possible is transmitted to the receiving terminal, and when the same BSS response message corresponding to the same BSS request message is received from the receiving terminal, data is transmitted to the receiving terminal.

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

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

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

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

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

[0053] At this time, the same BSS response message indicates that it can receive the data of the transmission terminal.

[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 value and the received signal strength of the other BSS request message is lower than the first CCA threshold value, the same BSS response message is transmitted to the transmission terminal, but the second CCA threshold value is set to a higher level than the first CCA threshold value.

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

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

[0057] According to still other embodiments, 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 for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal. The processor measures the signal strength of a wireless signal on a specific channel received via the transceiver, and determines whether the specific channel can be occupied based on the measured signal strength and the BSS identifier information of the wireless signal.

[0059] At this time, the processor uses the preamble information of the received wireless signal to obtain at least one of legacy wireless LAN information and non-legacy wireless LAN information. When the non-legacy wireless LAN information is obtained from the wireless signal, the processor determines whether the specific channel can be occupied based on the BSS identifier information of the wireless signal.

[0060] Further, the processor performs the determination based on the CCA for the specific channel, and the CCA threshold values used for the CCA are 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 that transmits and receives wireless signals, and a processor that controls the operation of the terminal. The processor measures the signal strength of a wireless signal on a specific channel received via the transceiver, obtains at least one of legacy wireless LAN information and non-legacy wireless LAN information using the preamble information of the received wireless signal, and determines whether the specific channel is occupied based on the BSS identifier information of the wireless signal when the measured signal strength is between a first CCA threshold value and a second CCA threshold value and non-legacy wireless LAN information is obtained from the wireless signal.

[0062] Next, the present invention provides a wireless communication terminal including a transceiver that transmits and receives wireless signals, and a processor that controls the operation of the terminal. The terminal receives a wireless signal on a specific channel via the transceiver, and the processor extracts the BSS identifier information of the received wireless signal. When the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal, the processor extracts length information from the wireless signal, where the length information indicates information regarding the time point when the transmission of the wireless signal is completed, and adjusts the 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 that transmits and receives wireless signals, and a processor that controls the operation of the terminal. The terminal receives a wireless signal on a specific channel via the transceiver. When the wireless signal has BSS identifier information different from that of the terminal, the processor performs a Clear Channel Assessment (CCA) based on a second CCA threshold higher than a first CCA threshold for a legacy terminal. If, as a result of performing the CCA, the channel is determined to be idle, the terminal performs a backoff procedure. If the backoff procedure is interrupted before the backoff counter for the backoff procedure expires, the backoff counter assigned to the terminal is adjusted. If the channel becomes even more idle, the backoff procedure is resumed using the adjusted backoff counter.

[0064] Next, the present invention provides a wireless communication terminal including a transceiver that transmits and receives wireless signals, and a processor that controls the operation of the terminal. The terminal receives a wireless signal having BSS identifier information different from that of the terminal via the transceiver. The processor is assigned a first backoff counter and a second backoff counter for the backoff procedure of the terminal, and performs a backoff procedure based on the received signal strength of the wireless signal. The backoff procedure consumes the first backoff counter if the received signal strength of the wireless signal is lower than a first CCA threshold for a legacy terminal, consumes 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 transmits data if 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 for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal. The terminal receives a request message (other BSS request message) having other BSS identifier information different from that of the terminal via the transceiver, receives a response message (other BSS response message) corresponding to the other BSS request message, and the processor determines whether the terminal can approach the channel 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 for transmitting and receiving wireless signals and a processor for controlling the operation of the terminal. The terminal receives a request message (other BSS request message) having other BSS identifier information different from that of the terminal via the transceiver, receives a response message (other 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 having the terminal as the recipient from a transmitting terminal, and the processor determines whether to transmit a same BSS response message corresponding to the same BSS request message based on the received signal strength of the other BSS request message and the received signal strength of the other BSS response message.

Advantages of the Invention

[0067] According to an embodiment of the present invention, it is possible to efficiently determine whether a wireless signal received in an overlapping BSS environment is the same wireless LAN signal, and based on this, it is possible to determine whether to adaptively utilize the corresponding channel.

[0068] According to another embodiment of the present invention, if the received wireless signal is a legacy wireless LAN signal from which BSS identifier information cannot be extracted, by collectively determining whether the channel can be occupied based on the received signal strength of the corresponding signal, it is possible to minimize the time delay required to additionally determine the BSS identifier of the legacy wireless LAN signal in the CCA process.

[0069] According to another embodiment of the present invention, when a wireless LAN signal having the same BSS identifier as the terminal is received, the inequality problem in which different CCA threshold values are applied depending on whether the corresponding wireless LAN signal includes non-legacy wireless LAN information can be solved. That is, for a wireless LAN signal having the same BSS identifier information as the terminal, by applying the same CCA threshold value for the legacy signal and the non-legacy signal, the fairness of channel occupancy between the legacy terminal and the non-legacy terminal can be maintained.

[0070] According to still another embodiment of the present invention, since at least a part of non-legacy wireless LAN information such as BSS identifier information can be obtained from the legacy preamble before confirming the non-legacy preamble, CCA can be performed in a shorter time.

[0071] According to still another embodiment of the present invention, when data transmission is performed in the spatial reuse section of the non-legacy terminal, the data transmission period of the corresponding terminal can be adjusted based on the length information extracted from the received wireless signal, and through this, the channel access delay problem of the legacy terminal can be solved.

[0072] Also, according to the embodiment of the present invention, a large number of terminals can effectively minimize mutual interference while communicating simultaneously.

Brief Description of the Drawings

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[0074] The terms used in this specification are generally selected as widely used terms as much as possible in consideration of the functions of the present invention, but this may vary depending on the intentions of those skilled in the art, conventions, or the emergence of new technologies. In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in this case, the meaning thereof is described in the description of the corresponding invention. Therefore, it is clarified that the terms used in this specification should be analyzed based on the substantial meaning of the terms and the content throughout this specification, rather than simply the names of the terms.

[0075] Throughout the specification, when a certain configuration is said to be "connected" to another configuration, this includes not only the case where it is "directly connected", but also the case where it is "electrically connected" with other components interposed therebetween. Also, when a certain configuration "includes" a specific component, this means that it further includes other components, rather than excluding other components, unless otherwise stated to the contrary. In addition, the limitations of "above" or "below" based on a specific critical value are appropriately replaced by "exceeding" or "less than" respectively according to the embodiments.

[0076] This application claims priority based on Republic of Korea Patent Registration Nos. 10-2014-0107321, 10-2014-0170812, and 10-2015-0035308, and the embodiments and descriptions described in each of the above applications serving as the basis for the priority are included in the detailed description of this application.

[0077] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. The wireless LAN system includes one or more Basic Service Sets (BSSs), where a BSS represents a set of devices that can successfully synchronize and communicate with each other. Generally, BSSs are classified into infrastructure BSSs and Independent BSSs (IBSSs). FIG. 1 shows an infrastructure BSS among them.

[0078] As shown in FIG. 1, the infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, STA5, access points PCP / AP-1 and PCP / AP-2 which are stations providing a Distribution Service, and a Distribution System (SD) connecting a number of access points PCP / AP-1 and PCP / AP-2.

[0079] A station (STA) is any device including a Medium Access Control (MAC) conforming to the IEEE 802.11 standard and a Physical Layer interface for a wireless medium, and in a broad sense includes not only non-access points (non-APs) but also access points (APs). Also, in this specification, the term "terminal" is used to refer to a non-AP STA or an AP, or both. A station for wireless communication includes a Processor and a transmit / receive unit, and may further include a user interface unit, a display unit, etc. according to an embodiment. The Processor generates a frame to be transmitted over a wireless network, or processes a frame received over the wireless network, and performs various other processes for controlling the station. And the transmit / receive unit is functionally connected to the Processor and transmits and receives frames for the station via a wireless network.

[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 itself. In an infrastructure BSS, in principle, communication between non-AP stations is performed via the AP, but when a direct link is set up, direct communication between non-AP stations becomes possible. On the other hand, in the present invention, the AP is used as including a PCP (Personal BSS Coordination Point), and in a broad sense, it includes all concepts such as a centralized controller, a base station (GS), a Node B, a BTS (Base Transceiver System), or a site controller.

[0081] A plurality of infrastructure BSSs are interconnected via a distribution system. At this time, a plurality of BSSs connected via the distribution system are defined as an extended service set (ESS).

[0082] FIG. 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, parts that are the same as or corresponding to those in the embodiment of FIG. 1 are not redundantly described.

[0083] Since the BSS3 shown in FIG. 2 is an independent BSS and does not include an AP, all stations STA6 and STA7 are in a state where they are not connected to the AP. An independent BSS is not allowed to be connected as a distribution system and forms a self-contained network. In an independent BSS, each of the stations STA6 and STA7 is 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, the 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 wireless LAN packets, and is installed inside or provided as an exterior of the station 100. According to an embodiment, the transceiver 120 includes at least one transceiver module that uses 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 that uses a frequency band of 6 GHz or higher and a transceiver module that uses a frequency band of 6 GHz or lower. Each transceiver module performs wireless communication with an AP or an external station according to the wireless LAN standard of the frequency band supported by the corresponding transceiver module. The transceiver 120 operates only one transceiver module at a time or operates a number of transceiver modules together simultaneously according to the performance and requirements of the station 100. When the station 100 includes a plurality of transceiver modules, each transceiver module may be provided in an independent form, or a plurality of modules may be integrated into one chip.

[0087] Next, the user interface unit 140 is provided in the station 100 and includes various forms 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 the instructions of the processor 110 using various output means.

[0088] Next, the display unit 150 outputs an image to the display screen. The display unit 150 outputs various display objects such as content performed by the processor 110 or a user interface based on the control instructions of the processor 110. Also, the memory 140 stores the control program used in the station 110 and various data thereby. Such a control program includes a connection program for the station 100 to connect to the AP or an external station as required.

[0089] The processor 110 of the present invention performs various instructions or programs and processes the data inside the station 100. Also, the processor 110 controls each unit of the station 100 described above and controls the data transmission and reception between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection to the AP stored in the memory 160 and receives the communication setting message transmitted by the AP. Also, the processor 110 interprets the information regarding the priority conditions of the station 100 included in the communication setting message and requests a connection to the AP based on the information regarding the priority conditions of the station 100. The processor 110 of the present invention may refer to the main control unit of the station 100, or may refer to a control unit for individually controlling a partial configuration of the station 100, for example, the transmission and reception unit 120, etc. according to an embodiment. The processor 110 controls various operations of wireless signal transmission and reception of the station 100 according to an embodiment of the present invention. Specific embodiments thereof will be described later.

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

[0091] FIG. 4 is a block diagram showing the configuration of the AP200 according to an embodiment of the present invention.

[0092] As shown in the figure, the AP200 according to an embodiment of the present invention includes a processor 210, a transceiver 220, and a memory 260. In FIG. 4, redundant descriptions are omitted for parts of the configuration of the AP200 that are the same as or correspond to the configuration of the station 100 in FIG. 3.

[0093] Referring to FIG. 4, the AP200 according to the present invention includes a transceiver 220 for operating a BSS in at least one frequency band. As described in the embodiment of FIG. 3, the transceiver 220 of the AP200 also includes a plurality of transceiver modules that utilize different frequency bands. That is, the AP200 according to an embodiment of the present invention includes two or more transceiver modules that utilize different frequency bands, for example, 2.4 GHz, 5 GHz, and 60 GHz. Preferably, the AP200 includes a transceiver module that utilizes a frequency band of 6 GHz or higher and a transceiver module that utilizes a frequency band of 6 GHz or lower. Each transceiver module performs wireless communication with a station according to the wireless LAN standard of the frequency band supported by the corresponding transceiver module. The transceiver 220 may operate only one transceiver module at a time or operate a number of transceiver modules together simultaneously according to the performance and requirements of the AP200.

[0094] Next, the memory 260 stores the control program used in the AP200 and various data thereby. Such a control program includes a management program for managing the connection of stations. Further, the processor 210 controls each unit of the AP200 and controls the data transmission and reception between the units. According to an embodiment of the present invention, the processor 210 executes a program for connection with the stations stored in the memory 260 and transmits a communication setting message for one or more stations. At this time, the communication setting message includes information regarding the connection priority conditions of each station. Further, the processor 210 performs connection setting in response to a connection request from a station. The processor 210 controls various operations of wireless signal transmission and reception of the AP200 according to an embodiment of the present invention. Specific embodiments thereof will be described later.

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

[0096] A terminal performing wireless LAN communication performs carrier sensing before transmitting data to check whether the channel is in an occupied state (busy). If a wireless signal of a certain intensity or more is sensed, it is determined that the corresponding channel is in an occupied state, and the terminal delays access to the corresponding channel. Such a process is called Clear Channel Assessment (CCA), and the level for determining the presence or absence of the corresponding signal sensing is called the CCA threshold. If a wireless signal equal to or higher than the CCA threshold received by the terminal has the terminal as the recipient, the terminal processes the received wireless signal. On the other hand, if no wireless signal is sensed on the corresponding channel or a wireless signal with an intensity smaller than the CCA threshold is sensed, it is determined that the channel is in an idle state.

[0097] If it is determined that the channel is in an idle state, each terminal with data to transmit performs a backoff procedure after a time of IFS (InterFrame Space) according to the status of each terminal, for example, AIFS (Arbitration IFS), PIFS (PCF IFS), etc. According to an embodiment, the AIFS is used as a configuration to replace the conventional DIFS (DCF IFS). Each terminal waits while reducing the slot time by only the random number assigned to the corresponding terminal during the interval of the idle state of the channel, and the terminal that has exhausted all the slot times attempts to access the corresponding channel. In this way, the section where each terminal performs the backoff procedure is called a contention window section.

[0098] If a specific terminal successfully accesses the channel, the corresponding terminal transmits data via the channel. However, if a terminal that attempts access collides with other terminals, the collided terminals are each assigned a new random number and perform a further backoff procedure. According to one embodiment, the new random number assigned to each terminal is determined within a range (2*CW) that is twice the range of the random number (contention window, CW) previously assigned to the corresponding terminal. On the other hand, each terminal attempts access by performing a further backoff procedure in the next contention window section. At this time, each terminal performs the backoff procedure from the slot time remaining in the previous contention window section. In this way, each terminal performing wireless LAN communication avoids mutual collisions with respect to a specific channel.

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

[0100] In wireless communication, for example, wireless LAN communication, the occupancy status of a channel is sensed via CCA. At this time, as the CCA method used, there are a signal detection (SD) method, an energy detection (ED) method, a correlation detection (CD) method, etc.

[0101] First, signal detection CCA-SD is a method for measuring the signal strength of the preamble of a wireless LAN (i.e., 802.11) frame. While this method enables stable signal detection, it has the drawback of operating only at the initial portion of frames where a preamble exists. According to one embodiment, signal detection is used for CCA with respect to the primary channel in a wideband wireless LAN. Next, energy detection CCA_ED is a method for sensing all signal energies received above a specific threshold value. This method is used for sensing wireless signals for which a preamble is not normally sensed, such as Bluetooth and ZigBee signals. Also, the method may be used for CCA on a secondary channel without continuously tracking the signal. On the other hand, correlation detection CCA-CD is a method for sensing the signal level even in the middle of a wireless LAN frame, and it utilizes the fact that a wireless LAN signal has a repeating pattern of periodic OFDM (Orthogonal Frequency Division Multiplex) signals. That is, the correlation detection method detects the signal strength with respect to the repeating pattern of OFDM signal symbols after receiving wireless LAN data at any given time.

[0102] According to an embodiment of the present invention, access of a terminal to a channel may be controlled using a preset CCA threshold value for each CCA method. According to the embodiment of FIG. 6, the CCA-ED threshold value 10 indicates a threshold value preset for performing energy detection, and the CCA-SD threshold value 30 indicates a threshold value preset for performing signal detection. Also, the receive sensitivity (RX Sensitivity) 50 indicates the minimum signal strength at which the terminal can demodulate a radio signal. According to the embodiment, the receive sensitivity 50 is set to be the same as or lower than the CCA-SD threshold value 30 depending on the performance and settings of the terminal. Also, the CCA-ED threshold value 10 is set to a higher level than the CCA-SD threshold value 30. For example, the CCA-ED threshold value 10 is set to -63 dBM and the CCA-SD threshold value 30 is set to -82 dBm, respectively. However, the present invention is not limited thereto, and the CCA-ED threshold value 10 and the CCA-SD threshold value 30 are set to be different depending on whether they are threshold values for various channels, the bandwidth of the channel on which CCA is performed, and the like.

[0103] According to the embodiment of FIG. 6, each terminal measures the signal strength (RX Received Signal Strengh Indicator, RS RSSI) of the received radio 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, when a radio signal 350 having a receive sensitivity of 50 or more received on a specific channel has a received signal strength (RX RSSI) equal to or less than the CCA-SD threshold value 30, the corresponding channel is determined to be in an idle state. Therefore, the received signal is not processed or protected by the terminal, and each terminal attempts to access the corresponding channel by the method described in FIG. 5 or the like.

[0105] If a wireless LAN signal 330 having a received signal strength (RX RSSI) equal to or greater than the CCA-SD threshold value of 30 is received on a specific channel, the corresponding channel is determined to be in an occupied state. Therefore, the terminal that received the corresponding signal delays access to the channel. According to one embodiment, the terminal determines whether the corresponding signal is a wireless LAN 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 in an occupied state not only when a wireless LAN signal of the same BSS as the corresponding terminal is received, but also when a wireless LAN signal of another BSS is received.

[0106] On the other hand, 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 in an occupied state. At this time, even when a wireless signal of a type other than a wireless LAN signal is received by the terminal, if the received signal strength of the corresponding signal is equal to or greater than the CCA-ED threshold value of 10, it is determined that the corresponding channel is in an occupied state. Therefore, the terminal that received the corresponding signal delays access to the channel.

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

[0108] As shown in FIG. 7, when STA-3 transmits upload data to AP-2, it may continuously interfere with STA-2 of BSS-1 located peripherally. At this time, the interference generated while BSS-1 and BSS-2 use the same frequency band (for example, 2.4 GHz, 5 GHz, etc.) and the same primary channel is called co-channel interference (CCI). Also, the interference generated while 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 value (for example, CCA-SD threshold value) of STA-2 depending on the distance between STA-2 and STA-3. If such interference is received by STA-2 at an intensity higher than the CCA threshold value, STA-2 will recognize that the corresponding channel is occupied and delay the upload data transmission of AP-1. However, since STA-2 and STA-3 are stations belonging to different BSSs, increasing the CCA threshold value of STA-2 will enable STA-2 and STA-3 to upload to AP-1 and AP-2 simultaneously, respectively, and the effect of spatial reuse can be improved.

[0109] On the other hand, the upload data transmission of STA-3 in BSS-2 in FIG. 7 will also interfere with STA-4 belonging to the same BSS-2. At this time, if the CCA threshold value of STA-4 is increased in the same way as STA-2, there is a risk of collision because STA-3 and STA-4 belonging to the same BSS will transmit upload data to AP-2 simultaneously. Therefore, in order to increase the CCA threshold value for any interference, it is necessary to determine whether the corresponding interference is induced by a signal belonging to the same BSS or a signal belonging to another BSS. For this purpose, each terminal should check the BSS identifier of the wireless LAN signal or other different forms of information that can distinguish BSSs. Also, it is preferable that such confirmation of BSS information is performed within a short time during which the CCA process is carried out.

[0110] Figures 8 to 13 are diagrams showing various embodiments of the CCA method according to the present invention. In the embodiments of Figures 8 to 13, the shaded areas indicate radio signals that are received by the terminal but ignored, i.e., unprotected radio signals. In other words, when a radio signal corresponding to the shaded area is received, the terminal determines that the corresponding channel is in an idle state. On the other hand, when a radio signal corresponding to an area that is not shaded is received, the terminal determines that the corresponding channel is in an occupied state. At this time, the received signal strength (RX Sensitivity) is set to be the same as or lower than the CCA-SD threshold value depending on the performance and settings of the terminal. Also, the CCA-ED threshold value is set to a higher level than the CCA-SD threshold value. Based on the result of determining whether the channel is occupied or not in each of the embodiments described later, the individual process described in Figure 5 is performed.

[0111] In each of the embodiments of Figures 8 to 10, the terminal measures the received signal strength (RX RSSI) of the received radio signal and determines whether the corresponding signal is a wireless LAN signal. If the received signal is a wireless LAN signal having BSS identifier information according to various embodiments described later, 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.

[0112] First, according to the embodiment of Figure 8, the CCA threshold value for the corresponding signal is determined based on whether the received radio signal is a wireless LAN signal having the same BSS identifier information as the BSS identifier information of the terminal. In the embodiment of the present invention, the BSS identifier information of the terminal is the BSS identifier information assigned to the corresponding terminal, and if the corresponding terminal is a non-AP STA, it indicates the identifier information (e.g., the MAC address of the AP) of the AP to which the corresponding terminal is connected or attempting to connect, or the reduced information thereof. At this time, the terminal receives the BSS identifier information from the AP, and the received BSS identifier information is stored in the terminal.

[0113] Referring to FIG. 8, if the received radio signal of a specific channel is a wireless LAN signal having a received signal co - reception (RX RSSI) with a reception sensitivity of 50 or more and a CCA - SD threshold value of 30 or less, it is determined whether the corresponding signal is a wireless LAN signal having the same BSS identifier information as the terminal, and based on this, whether the channel can be occupied is determined. If the BSS identifier information extracted from the radio signal is different from the BSS identifier information of the terminal (i.e., if it is an OBSS wireless LAN signal 452), the corresponding channel is determined to be in an idle state. However, if the BSS identifier information extracted from the radio signal is the same as the BSS identifier information of the terminal (i.e., if it is a MYBSS wireless LAN signal 454), the corresponding channel is determined to be in an occupied state.

[0114] On the other hand, if the received radio signal of a specific channel is a wireless LAN signal 430 having a received signal strength (RX RSSI) between the CCA - SD threshold value of 30 and the CCA - ED threshold value of 10, the corresponding channel is determined to be in an occupied state. At this time, the terminal that has received the wireless LAN signal 430 determines that the channel where the signal is received is in an occupied state not only when the corresponding signal is a wireless LAN signal having the same BSS identifier information as the terminal, but also when it is a wireless LAN signal having other BSS identifier information.

[0115] In the energy detection process, if the received radio signal of a specific channel by the terminal is a wireless signal 410 having a received signal strength (RX RSSI) of 10 or more of the CCA - ED threshold value, the corresponding channel is determined to be in an occupied state. As described above, even when the terminal receives a wireless signal of a type other than a wireless LAN signal, if the received signal strength (RX RSSI) of the wireless signal is 10 or more of the CCA - ED threshold value, it is determined that the corresponding channel is in an occupied state.

[0116] As described above, according to the embodiment of FIG. 8, the CCA threshold value applied to a wireless LAN signal having the same BSS identifier information as the terminal has different levels from the CCA threshold value applied to a wireless LAN signal having BSS identifier information different from the terminal. According to one embodiment, the CCA threshold value applied to a wireless LAN signal having BSS identifier information different from the terminal is set to a higher level than the CCA threshold value applied to a wireless LAN signal having the same BSS identifier information as the terminal. According to the embodiment of FIG. 8, the preset CCA-SD threshold value 30 is applied to the CCA threshold value for a wireless LAN signal having BSS identifier information different from the terminal, and the reception sensitivity 50 level of the terminal is applied to the CCA threshold value for a wireless LAN signal having the same BSS identifier information as the terminal.

[0117] FIGS. 9 and 10 are diagrams showing other embodiments of the CCA method using BSS identifier information. In the embodiments of FIGS. 9 and 10, the same or corresponding parts as those in the embodiment of FIG. 8 are not described repeatedly.

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

[0119] Referring to FIG. 9, if the received signal strength (RX RSSI) of the wireless signal of the received specific channel is 50 or more of the reception sensitivity and 40 or less of the CCA-SD threshold value, the corresponding channel is determined to be in an idle state. At this time, the terminal determines that the channel where the signal is received is in an idle state for both cases where the received signal is a wireless LAN signal 454 having the same BSS identifier information as the terminal and a wireless LAN signal 452 having other different identifier information.

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

[0121] In the embodiment of FIG. 9, the second CCA-SD threshold value of 20 is for performing signal detection on a wireless LAN signal having BSS identifier information different from that of the terminal, and is set to be greater than the first CCA-SD threshold value of 40 and less than or equal to the CCA-ED threshold value.

[0122] On the other hand, if the received wireless signal of a specific channel is a wireless LAN signal 420 having a received signal strength (RX RSSI) between the second CCA-SD threshold value of 20 and the second CCA-ED threshold value of 10, the corresponding channel is determined to be in an occupied state. At this time, the terminal that has received the wireless LAN signal 420 determines that the channel on which the corresponding signal is received is in an occupied state not only when the corresponding signal is a wireless LAN signal having the same BSS identifier information as the terminal, but also when the corresponding signal is a wireless LAN signal having other BSS identifier information.

[0123] In the energy detection process, if the received wireless signal of a specific channel 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 in an occupied state. As described above, even when the terminal receives a wireless signal of a type other than a wireless LAN signal, if the received signal strength (RX RSSI) of the wireless signal is equal to or greater than the CCA-ED threshold value of 10, it is determined that the corresponding channel is in an occupied state.

[0124] Thus, according to the embodiment of FIG. 9, the CCA threshold value applied to the wireless LAN signal having the same BSS identifier information as the terminal has a different level from the CCA threshold value applied to the wireless LAN signal having BSS identifier information different from the terminal. That is, as the CCA threshold value for the wireless LAN signal having the same BSS identifier information as the terminal, the preset first CCA-SD threshold value 40 is applied, and as the CCA threshold value for the wireless LAN signal having BSS identifier information different from the terminal, the preset second CCA-SD threshold value 20 is applied. Here, the second CCA-SD threshold value 20 is set higher than the first CCA-SD threshold value 40 and lower than or at the same level as the CCA-ED threshold value.

[0125] Next, according to the embodiment of FIG. 10, if the received signal strength (RX RSSI) of the received wireless signal on a specific channel is 50 or more, signal detection is performed based on whether the corresponding signal is a wireless LAN 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 50 or more and it is a wireless LAN 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 50 or more and it is a wireless LAN signal 451 having BSS identifier information different from the terminal, the corresponding channel is determined to be in an idle state.

[0127] On one hand, 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 of 10, the corresponding channel is determined to be in an occupied state. Regardless of whether the corresponding signal is a wireless LAN signal having the same BSS identifier information as the terminal, and regardless of whether the corresponding signal is a wireless LAN signal or not, the terminal determines that the corresponding channel is in an occupied state. Therefore, if a wireless LAN signal having BSS identifier information different from that of the terminal is received at a level higher than the CCA-ED threshold of 10, the corresponding channel is determined to be in an occupied state by the energy detection process.

[0128] Thus, according to the embodiment of FIG. 10, in the signal detection process, the terminal does not use a separately set CCA-SD threshold, and determines whether the channel can be occupied based on whether the received wireless signal is a wireless LAN signal having the same BSS identifier information as the terminal. However, since the terminal uses a preset CCA-ED threshold of 10 for energy detection, collisions with wireless LAN signals having BSS identifier information different from that of the terminal can be avoided.

[0129] FIGS. 11 to 13 are diagrams showing other embodiments of the method for obtaining non-legacy wireless LAN information and CCA using BSS identifier information. In each of the embodiments of FIGS. 11 to 13, the terminal measures the received signal strength (RX RSSI) of the received wireless signal and determines whether the corresponding signal is a wireless LAN signal. If the received signal is a wireless LAN 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 wireless LAN information and non-legacy wireless LAN information from the received wireless signal. Through this, the terminal determines whether the received wireless signal is a signal containing only legacy wireless LAN information or a signal containing both a legacy wireless LAN signal and a non-legacy wireless LAN signal. According to one embodiment, the terminal uses the preamble information of the received wireless signal to acquire at least one of legacy wireless LAN information and non-legacy wireless LAN information. The BSS identifier information of the wireless signal is extracted from the non-legacy wireless LAN information if non-legacy wireless LAN information is acquired from the corresponding signal. However, the present invention is not limited to this, and it may be extracted from the legacy wireless LAN information according to various embodiments described later. According to one embodiment of the present invention, the BSS identifier information referred to for performing CCA is included in the non-legacy wireless LAN information, while the received wireless signal may not include non-legacy wireless LAN information. That is, if the received wireless signal does not include the BSS identifier information referred to for performing CCA according to the 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 preset value. According to another embodiment, if the received wireless signal is a non-legacy wireless LAN signal that does not include the BSS identification information according to the embodiment of the present invention, other information of the corresponding signal, such as PBSSID (Partial BSSID), PAID (Partial Association ID), PHY layer header information, a specific preamble signal pattern, etc., is used to estimate the BSS identifier information of the corresponding signal. In the embodiments of FIGS. 11 to 13, the same or corresponding parts as those in the above-described embodiments are not redundantly described.

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

[0132] If the BSS identifier information extracted from the wireless signal is different from the BSS identifier information of the terminal (i.e., if it is an OBSS wireless LAN signal), the corresponding channel is determined to be in an idle state. At this time, the OBSS wireless LAN signal 552 is classified into an OBSS non-legacy wireless LAN signal from which non-legacy wireless LAN information is obtained from the corresponding signal and an OBSS legacy wireless LAN signal from which non-legacy wireless LAN information is not obtained. The terminal determines that the corresponding channel is in an idle state both when an OBSS non-legacy wireless LAN signal is received and when an OBSS legacy wireless LAN 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 wireless LAN signal), the corresponding channel is determined to be in an occupied state. Similarly, the MYBSS wireless LAN signal 2 is classified into a MYBSS non-legacy wireless LAN signal 558 from which non-legacy wireless LAN information is obtained from the corresponding signal and a MYBSS legacy wireless LAN signal 556 from which non-legacy wireless LAN information is not obtained. The terminal determines that the corresponding channel is in an occupied state both when the MYBSS non-legacy wireless LAN signal 558 is received and when the MYBSS legacy wireless LAN signal 556 is received.

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

[0135] If non-legacy wireless LAN information is obtained in a wireless LAN signal and the BSS identifier information of the corresponding signal is different from the BSS identifier information of the terminal (i.e., if it is a non-legacy OBSS signal 542), the corresponding channel is determined to be in an idle state. However, in other cases, that is, if non-legacy wireless LAN information is not obtained from the wireless signal (i.e., a legacy signal), or if the BSS identifier information of the corresponding signal is the same as that of the terminal (i.e., a MYBSS signal), the corresponding channel is determined to be in an occupied state. More specifically, the cases where the channel is determined to be in an occupied state are as follows: i) when non-legacy wireless LAN information is not obtained 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 non-legacy OBSS signal 544), ii) when non-legacy wireless LAN information is not obtained from the wireless signal and the BSS identifier information of the corresponding signal is the same as that of the terminal (i.e., when it is a legacy MYBSS signal 546), and iii) when non-legacy wireless LAN information is obtained from the wireless signal and the BSS identifier information of the corresponding signal is the same as that of the terminal (i.e., when it is a non-legacy MYBSS signal 548).

[0136] That is, if non-legacy wireless LAN information is not obtained from the wireless signal, the corresponding channel is determined to be in an occupied state, but if non-legacy wireless LAN information is obtained from the wireless signal, whether the channel can be occupied is determined based on whether the BSS identifier information of the corresponding signal is the same as that of the terminal. Therefore, according to the embodiments of the present invention, when non-legacy wireless LAN information is obtained from the wireless signal, whether the corresponding channel can be occupied is determined based on the BSS identifier information of the wireless signal. According to one embodiment, if non-legacy wireless LAN information is not obtained from the wireless signal, there is a possibility that the BSS identifier information referred to for performing the CCA of the present invention cannot be extracted from the corresponding signal. At this time, regardless of whether the BSS identifier information is extracted from the corresponding signal, the terminal determines that the channel is in an occupied state.

[0137] Such a signal detection process is performed with reference to the preamble of the received radio signal. According to one embodiment, when it is determined in signal detection that the channel is in an occupied state, even if the received signal strength (RX RSSI) drops below the first CCA-SD threshold value of 40 while receiving a protected radio signal, the terminal does not have to access the channel during the frame transmission time of the radio signal.

[0138] On the other hand, if the radio signal of a specific channel received is a wireless LAN signal 520 between the second CCA-SD threshold value of 20 and the CCA-ED threshold value of 10, the corresponding channel is determined to be in an occupied state. At this time, regardless of whether non-legacy wireless LAN information is obtained from the corresponding signal, and regardless of whether the corresponding signal is a wireless LAN signal having the same BSS identifier information as the terminal, the terminal determines that the channel on which the corresponding signal is received is in an occupied state.

[0139] In the energy detection process, if the radio signal of a specific channel received by the terminal is a radio signal 510 with a CCA-ED threshold value of 10 or more, the corresponding channel is determined to be in an occupied state. As described above, even when the terminal receives a radio signal of another type instead of a wireless LAN signal, if the received signal strength (RX RSSI) of the radio signal is 10 or more of the CCA-ED threshold value, it is determined that the corresponding channel is in an occupied state.

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

[0141] If non-legacy wireless LAN information is obtained 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., if it is a non-legacy wireless LAN information MYBSS558 signal), the corresponding channel is determined to be in an occupied state. However, in other cases, that is, if the BSS identifier information of the wireless signal is different from the BSS identifier information of the terminal (i.e., an OBSS signal), or if non-legacy wireless LAN information is not obtained from the corresponding signal (i.e., a legacy signal), the corresponding channel is determined to be in an idle state. More specifically, the cases where the channel is determined to be in an idle state include: i) when non-legacy wireless LAN information is obtained from a 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) when non-legacy wireless LAN information is not obtained from a 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) when non-legacy wireless LAN information is not obtained 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., when it is a legacy MYBSS signal 556).

[0142] That is, if non-legacy wireless LAN information is not obtained from the wireless signal, the corresponding channel is determined to be in an idle state. However, if non-legacy wireless LAN information is obtained from the wireless signal, whether the channel can be 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. According to the embodiment of FIG. 12, if non-legacy wireless LAN information is obtained from the wireless signal and the BSS identifier information of the corresponding signal is different from the BSS identifier information of the terminal, the preset CCA threshold 20 is used for the CCA of the corresponding channel. However, if non-legacy wireless LAN information is obtained from the wireless signal and the BSS identifier information of the corresponding signal is the same as the BSS identifier information of the terminal, if the corresponding signal has a received signal strength of 50 or more without setting a separate CCA threshold, the corresponding channel is determined to be in an occupied state. According to one embodiment, if non-legacy wireless LAN information is not obtained from the wireless signal, there is a possibility that the BSS identifier information referred to for performing the CCA of the present invention is not extracted from the corresponding signal. At this time, regardless of whether the BSS identifier information is extracted from the corresponding signal, the terminal determines that the channel is in an idle state.

[0143] According to the embodiment of FIG. 12, the BSS identifier information referred to for performing CCA is included in the non-legacy wireless LAN information, and even when the received wireless LAN signal does not include such non-legacy wireless LAN information, efficient CCA can be performed. That is, if the received wireless signal is a legacy wireless signal from which the BSS identifier information is not extracted, by collectively determining whether the corresponding channel is in an idle state or an occupied state based on the received signal strength of the corresponding signal, the time delay required to determine whether the BSS identifier of the legacy wireless LAN signal is actually the same as the BSS identifier of the terminal can be minimized. That is, the terminal additionally checks the BSS identifier information and determines the idle / occupied state of the channel only when the wireless signal is a non-legacy wireless LAN signal.

[0144] Next, according to the embodiment of FIG. 13, if the received radio signal of a specific channel has a received signal strength (RX RSSI) that is 50 or more of the reception sensitivity and 40 or less of the first CCA-SD threshold value, the corresponding channel is determined to be in an idle state. At this time, regardless of whether the received signal includes non-legacy wireless LAN information and whether it has the same BSS identifier information as the terminal, the corresponding channel is determined to be in an idle state. Also, according to the embodiment of FIG. 13, when non-legacy wireless LAN information is obtained from the radio signal and the BSS identifier information of the corresponding signal is the same as the BSS identifier information of the terminal, the first CCA-SD threshold value of 40 is used for the CCA of the corresponding channel. However, when non-legacy wireless LAN information is obtained from the radio signal and the BSS identifier information of the corresponding signal is different from the BSS identifier information of the terminal, a second CCA-SD threshold value of 20, which is higher than the first CCA-SD threshold value of 40, is used for the CCA of the corresponding channel.

[0145] According to the embodiment of FIG. 13, when a wireless LAN signal having the same BSS identifier as the terminal is received, it is possible to solve the inequality problem in which different CCA threshold values are applied depending on whether the corresponding wireless LAN signal includes non-legacy wireless LAN information. That is, by applying the same CCA threshold value to the legacy MYBSS signal and the non-legacy MYBSS signal, it is possible to maintain fairness in channel occupancy between the legacy terminal and the non-legacy terminal.

[0146] On the other hand, in the embodiments of FIGS. 12 and 13, the CCA process when a radio signal having a received signal strength (RX RSSI) of 40 or more of the first CCA-SD threshold value is received is performed in the same manner as in the embodiment of FIG. 11 described above.

[0147] FIG. 14 is a diagram showing a frame structure of a wireless LAN signal according to an embodiment of the present invention. Referring to FIG. 14, a wireless LAN signal according to an embodiment of the present invention includes a legacy preamble 710 for a legacy terminal (for example, a terminal such as 802.11a / g) and a non-legacy preamble 720 for a non-legacy terminal (for example, an 802.11ax terminal). First, the legacy preamble 710 includes legacy wireless information that can be decoded by a legacy terminal, such as L-STF, L-LTF, L-SIG fields, etc. Next, the non-legacy preamble 720 includes non-legacy wireless LAN information that can be coded only by a non-legacy terminal, and the non-legacy wireless LAN information cannot be decoded by a legacy terminal. On the other hand, the legacy preamble 710 may include at least a part of non-legacy wireless LAN information that can be decoded by a non-legacy terminal depending on an embodiment. In addition, the non-legacy preamble 720 may include information in which at least one field of the legacy preamble 710, for example, a part or all of the L-SIG field, is repeated.

[0148] According to an embodiment of the present invention, the BSS identifier information referred to for performing CCA is included in the non-legacy preamble 720 as non-legacy wireless LAN information. At this time, the BSS identifier information is extracted from a preset bit field of the non-legacy preamble 720. On the other hand, according to another embodiment of the present invention, the BSS identifier information is extracted from additional information of the legacy preamble 710. For example, as will be described later, the legacy preamble 710 includes non-legacy wireless LAN information via an additional sub-carrier set or the like, and the BSS identifier information is obtained from the non-legacy wireless LAN information included in the legacy preamble 710. According to still another embodiment of the present invention, the BSS identifier information may be extracted from a preset bit field of the legacy preamble 710. At this time, the preset bit field of the legacy preamble 710 may be a bit field set for the legacy terminal, and the value of the corresponding bit field may be used as the BSS identifier information under specific conditions as will be described later.

[0149] FIG. 15 is a diagram showing a method of indicating 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 of the non-legacy preamble 720 in FIG. 14. According to an embodiment of the present invention, the BSS identifier information is reduced information of the BSS identifier assigned to each BSS, and has fewer bits than the actual BSS identifier. For example, in a specific wireless LAN system, when the BSS identifier is represented by information of 24 bits, the BSS identifier information is represented by a bit field having a preset length in the range of 1 bit to 23 bits. In the present invention, the BSS identifier information is information obtained by classifying the actual BSS identifier into a preset category, and is also referred to as a BSS color. As a method of actually obtaining the BSS color reduced from the BSS identifier, there are a method of using a combination of bit values at preset positions of the BSS identifier, a method of using a result value obtained by applying a preset hash function to the BSS identifier, and the like.

[0150] FIG. 15 shows an example in this regard, and shows the result of obtaining a BSS color by using the last three bit values of the BSS identifier. In this way, although the BSS color is included in the preamble of the wireless LAN signal with an amount of information less than that of the actual BSS identifier, each terminal can thereby efficiently determine in a short time whether the received wireless LAN signal is a signal having the same BSS identifier as the corresponding terminal. Such a BSS identifier is represented by preset bits of a non-legacy preamble.

[0151] On the other hand, according to an embodiment of the present invention, the non-legacy preamble 720 includes a repeated L-SIG field, and the repeated L-SIG field is set such that at least some bits are the same as the L-SIG field of the legacy preamble 710. At this time, the bits different from the L-SIG field of the legacy preamble 710 among the repeated L-SIG fields indicate BSS identifier information, system bandwidth information, non-legacy wireless LAN system information, channel information, and the like.

[0152] According to an additional embodiment of the present invention, additional information is transmitted via a modulation method applied to the repeated L-SIG field. That is, the repeated L-SIG field may be represented by the same modulation value as the L-SIG field of the legacy preamble 710, or may be represented by an opposite modulation value. Here, the opposite modulation value is indicated via a phase transition between the modulation symbols transmitted to the L-SIG of the legacy preamble 710 and the repeated L-SIG modulation symbols, and additional information transmission becomes possible via the amount of phase change. Specifically, if (1,1) is multiplied and transmitted to the L-SIG of the legacy preamble 710 and the repeated L-SIG, the symbols of both fields will have the same phase, and if (1, -1) is multiplied and transmitted, a 180-degree phase transition will occur between the symbols of the repeated L-SIG and the symbols of the legacy preamble 710. At this time, specific flag information for non-legacy wireless LAN information is determined depending on whether the repeated L-SIG field is represented by 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 has a 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] FIGS. 16 and 17 are other embodiments of the present invention, and are diagrams showing a method of obtaining non-legacy wireless LAN information using an additional subcarrier set of a wireless LAN signal.

[0154] First, FIG. 16 is a diagram showing an example of a subcarrier configuration used in the legacy preamble of a wireless LAN signal. According to an embodiment of the present invention, the subcarrier set of the legacy preamble of a non-legacy wireless LAN signal is configured in the same way as the subcarrier set of a legacy wireless LAN signal. That is, the subcarrier set of the legacy preamble is composed of a total of 52 subcarriers including 4 pilot subcarriers and 48 data subcarriers with a bandwidth of 20 MHz. At this time, when the numbers of each subcarrier are set to -26, -25, …, -2, -1, 1, 2, …, 25, 26, the subcarriers having the numbers -21, -7, 7, 21 are used as pilot subcarriers, and the subcarriers with the remaining numbers are used as data subcarriers. Such a basic configuration of subcarriers is necessary to maintain compatibility between a legacy wireless LAN system (e.g., 802.11a / g) and a non-legacy wireless LAN system (e.g., 802.11ax, etc.) in an environment where they coexist. That is, by making the legacy preamble of not only the legacy signal but also the non-legacy wireless LAN signal have a subcarrier configuration as shown in FIG. 16, backward compatibility with legacy terminals can be provided.

[0155] FIG. 17 shows an example of a subcarrier configuration used for a non-legacy wireless LAN signal. With the development of filters, amplifiers, etc. used in terminals, additional subcarriers can be used in a non-legacy wireless LAN system without being interfered with by adjacent bandwidths. Referring to FIG. 17, the subcarriers of the non-legacy wireless LAN signal according to an embodiment of the present invention are configured to include a first subcarrier set 800 and a second subcarrier set 820. More specifically, the first subcarrier set 800 is configured in the same way as the subcarrier set of the legacy wireless LAN signal shown in FIG. 16. Also, the second subcarrier set 820 is a subcarrier set different from the first subcarrier set 800 and includes a total of four additional subcarriers, two each at the upper and lower indexes of the first subcarrier set 800 according to one embodiment. According to the embodiment of FIG. 17, since the non-legacy wireless LAN signal uses pilot subcarriers at the same positions and numbers as the legacy wireless LAN signal, it comes to use 52 data subcarriers, which is an increase of 4 from the conventional 48. According to one embodiment, such a subcarrier configuration is used after the legacy preamble part of the non-legacy wireless LAN signal. The non-legacy terminal obtains it via a total of 56 subcarriers from the non-legacy preamble and data field of the received non-legacy wireless LAN signal, respectively.

[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 wireless LAN system information, channel information, etc. At this time, a separate parity bit for 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 wireless LAN system information, channel information, etc. are expressed via the second subcarrier set 820 of the repeated L-SIG field.

[0157] On the other hand, according to another embodiment of the present invention, the sub-carrier configuration of FIG. 17 is extended and applied to the legacy preamble of the non-legacy wireless LAN signal. That is, the legacy preamble of the non-legacy wireless LAN signal additionally includes a second sub-carrier set 820 and transmits non-legacy wireless LAN information via the second sub-carrier set 280. At this time, the legacy terminal cannot obtain information from the second sub-carrier set 820, but the non-legacy terminal can obtain additional information from the second sub-carrier set 820 of the legacy preamble.

[0158] For example, assuming that the second sub-carrier set 820 additionally used in the legacy preamble includes four sub-carriers, the indexes (i.e., sub-carrier numbers) of the corresponding sub-carriers are set to -28, -27, 28, 28 as shown in FIG. 17, respectively. At this time, if the BPSK modulation method is used for the legacy preamble and the same modulation method is applied to the second sub-carrier set, a total of 4 bits of information are additionally transmitted. Similarly, when the QPSK modulation method is applied to the second sub-carrier set, a total of 8 bits of information are additionally transmitted. At this time, parity bits for parity check are included in the non-legacy preamble of the second sub-carrier set included in the legacy preamble.

[0159] According to an additional embodiment of the present invention, only a part of the total bits shown in the second sub-carrier set 820 of the legacy preamble is used for additional information transmission. For example, in the second sub-carrier set 820, only some bits are used for additional information transmission for compatibility with the parity check of the legacy preamble. That is, for compatibility with the parity bits conventionally used in the L-SIG, the information added by the second sub-carrier set 820 has an even parity. When using the BPSK modulation method, the information that can be transmitted via the second sub-carrier set 820 is a total of 3-bit information of 1010, 0101, 1100, 0011, 1001, 0110, 1111, 0000.

[0160] According to another embodiment, specific bits of the second sub-carrier set 820 are used as parity check bits, and the remaining bits are used for additional information transmission. For example, among the 4 bits of the second sub-carrier set 820, 3 bits are used for additional information transmission, and 1 bit is used as a parity bit. At this time, the parity bit of the second sub-carrier set 820 may be used for the parity check for the bits added by the second sub-carrier set 820, or may be used for the parity check for the entire L-SIG including the second sub-carrier set 820. In this case, for the legacy wireless LAN signal, the conventional parity bits of the L-SIG may be used for parity check. For the non-legacy wireless LAN signal, by using both the conventional parity bits of the L-SIG and the parity bits of the second sub-carrier set 820 for parity check, a more reliable parity check can be achieved. Also, according to another embodiment, the parity check for the non-legacy wireless LAN information added by the second sub-carrier set 820 may be performed using the reserved bits of the L-SIG.

[0161] In this way, when additional information for a non-legacy terminal is transmitted via the second sub-carrier set 820 of the legacy preamble, the non-legacy terminal can obtain the additional information more quickly with the legacy preamble of the received wireless LAN signal and use this to reduce the detection of initial connection delays and unnecessary preambles, headers, packets, etc. Also, according to an embodiment of the present invention, the non-legacy terminal obtains non-legacy wireless LAN information from the second sub-carrier set 820 of the legacy preamble. At this time, the non-legacy wireless LAN information obtained includes the BSS identifier information, system bandwidth information, non-legacy wireless LAN system information, channel information, etc. described above. When the second sub-carrier set 820 is obtained with the legacy preamble of the received wireless LAN signal, the non-legacy terminal recognizes that the corresponding wireless LAN signal includes non-legacy wireless LAN information.

[0162] In the embodiment of FIG. 17, an example in which the second sub-carrier set 820 includes four additional data sub-carriers has been described. However, the present invention is not limited to this, and other numbers of sub-carriers different from this may be included in the second sub-carrier set 820. Also, in the embodiment of FIG. 17, it is applicable not only when the bandwidth of the wireless LAN signal is 20 MHz, but also when other bandwidths such as 40 MHz, 80 MHz, and 160 MHz are used.

[0163] FIG. 18 is another embodiment of the present invention and shows a method of indicating non-legacy wireless LAN information using a preset bit field of a legacy preamble.

[0164] According to an additional embodiment of the present invention, non-legacy wireless LAN information is extracted from a preset bit field of a legacy preamble under specific conditions. FIG. 18 is an example thereof, showing a rate bit feed included in the L-SIG of the legacy preamble. As shown, 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 coding rate of the legacy wireless LAN signal is obtained through the values of the previous three bits of the Rate bit field. Thus, according to an embodiment of the present invention, it is possible to determine whether the corresponding Rate bit field indicates non-legacy wireless LAN information based on the value of the fourth bit of the Rate bit field. That is, when the fourth bit of the Rate bit field has a value of 1, the corresponding Rate bit field indicates conventional information, that is, the data rate, modulation method, and coding rate. However, when the fourth bit of the Rate bit field has a value of 0, the corresponding Rate bit field indicates non-legacy wireless LAN information.

[0165] When it is determined that the Rate bit field contains non-legacy wireless LAN information, as illustrated in FIG. 18, BSS identifier information is extracted from the first three bit values before the corresponding Rate bit field. However, the present invention is not limited to this, and non-legacy wireless LAN information such as bandwidth information, channel information, and Association Identifier (AID) of the non-legacy wireless LAN signal may be extracted from the Rate bit field. At this time, the actual Rate information for the non-legacy terminal is transmitted via the non-legacy preamble. On the other hand, even when the Rate bit field contains non-legacy wireless LAN information, the legacy terminal analyzes this as Rate information. Due to such a situation, by appropriately setting the length field of the L-SIG, when the legacy terminal requires a transmission delay for the transmission of other terminals, the legacy terminal uses the L-SIG length information of other terminal packets to perform a transmission delay (such as NAV setting). More specifically, since the length field of the legacy preamble indicates the size (number of bytes) of the 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 when the length field is divided using this information, the required number of OFDM symbols can be known. At this time, the NAV (Network Allocation Vector) is set according to the obtained number of OFDM symbols. However, when the Rate bit field is utilized as non-legacy wireless LAN information according to an embodiment of the present invention, the length field may be adjusted so that the NAV can be set to only the required length.

[0166] Thus, according to the embodiments of the present invention, based on the information in the preset specific bits of the legacy preamble, it is determined whether the corresponding legacy preamble contains non-legacy wireless LAN information. If it is determined that the legacy preamble contains non-legacy wireless LAN information, non-legacy wireless LAN information such as BSS identifier information is extracted from the preset bit field of the legacy preamble, for example, the Rate bit field.

[0167] On the other hand, according to an additional embodiment of the present invention, a combination of the second sub-carrier set of the above-mentioned legacy preamble and the specific bit field (for example, the Rate bit field) can be used to check more bits, and non-legacy wireless LAN information can be transmitted through this. For example, when the legacy preamble is additionally configured to include a second sub-carrier set, the terminal determines that the corresponding legacy preamble contains non-legacy wireless LAN information, and extracts all four bits of the Rate bit field or BSS identifier information. Further, when the legacy preamble is additionally configured to include a second sub-carrier set, the non-legacy terminal may analyze the entire L-SIG bit field of the legacy preamble as non-legacy wireless LAN information. Thus, according to the embodiment of FIG. 18, before checking the non-legacy preamble, at least a part of non-legacy wireless LAN information such as BSS identifier information can be obtained from the legacy preamble, so that CCA can be performed in a shorter time.

[0168] FIG. 19 is a diagram showing an inequality problem of legacy terminals that may occur when the CCA threshold value adjusted according to an embodiment of the present invention is used for channel access. In FIG. 19 and the subsequent embodiments, MT (MYBSS Transmitter) and MR (MYBSS Receiver) respectively indicate a transmission terminal and a reception terminal of the first BSS (MYBSS), and OT (OBSS Transmitter) and OR (OBSS Receiver) indicate a transmission terminal and a reception terminal of a different second BSS (OBSSS). Also, MT, MR, OT, and OR are non-legacy terminals, and it is assumed that L is a legacy terminal.

[0169] As shown in FIG. 19, in 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). At this time, if the received signal strength of the wireless signal O_DATA is higher than the above-described first CCA threshold value CCA-SD1 for the legacy terminal L located around the terminals OT and OR, it is determined that the channel is in an occupied state and the channel access is not performed. At this time, the channel access delay period 810 of the legacy terminal L is set until the transmission of the response message (O_ACK) of the terminal OR is completed.

[0170] On the other hand, the terminal MT of OBSS and the other BSS, MYBSS, determines whether the channel can be occupied 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-described embodiment. That is, when the BSS identifier information of the received wireless signal O_DATA is different from the BSS identifier information of the corresponding terminal, the terminal MT performs CCA based on the above-described second CCA threshold value CCA-SD2. At this time, the second CCA threshold value CCA-SD2 has a higher level than the first CCA threshold value CCA-SD1 used for legacy terminals. Therefore, assuming that O_DATA is received by the legacy terminal L and the non-legacy terminal MT at a received signal strength between the first CCA threshold value CCA-SD1 and the second CCA threshold value CCA-SD2, the channel access of the legacy terminal L is delayed, 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 value CCA-SD2, the terminal MT determines that the corresponding channel is in an idle state and approaches the channel. That is, the terminal MT performs a backoff procedure and transmits data (MY_DATA) when the backoff counter in the backoff procedure expires. Also, the terminal MR that has received MY_DATA from the terminal MT transmits a response message (MY_ACK) in response. At this time, if the transmission of the wireless signals MY_DATA and MY_ACK exchanged between the terminal MT and MR ends lower than the channel deferral period 810 set for the legacy terminal L, the legacy terminal L cannot approach the channel even during the additional period 820 after the channel deferral period 810. Such a problem can occur not only during terminal MPDU transmission but also in the transmission situation based on TXOP (Transmission Opportunity) or A-MPDU (Aggregate MPDU).

[0172] FIGS. 20 to 23 are diagrams showing a data transmission method of a non-legacy terminal for solving the channel access delay problem of a legacy terminal.

[0173] First, FIG. 20 is a diagram showing the frame structure of a non-legacy wireless LAN signal according to an embodiment of the present invention. Referring to FIG. 20, the non-legacy wireless LAN signal includes a preamble 910, an L-SIG field 920 for legacy terminals (e.g., terminals such as 802.11a / g), a HEW-SIG field 930 for non-legacy terminals (e.g., 802.11ax terminals), and a MAC header field 940. In an embodiment of the present invention, the L-SIG field 920 indicates at least a part of the legacy preamble, and the HEW-SIG field 930 indicates at least a part of the non-legacy preamble. According to an embodiment of the present invention, the L-SIG field 920, the HEW-SIG field 930, and the MAC header 940 each include length information indicating the transmission length of data. 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, respectively. 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, respectively, but the present invention is not limited thereto.

[0174] According to an embodiment of the present invention, LEN-1 indicates the corresponding frame length information. At this time, the frame length information is expressed as time information required for the transmission of the frame, or is expressed as the size (number of bytes) information of data that can infer the time required for transmission in combination with other information. On the other hand, LEN-2 indicates the length information until the transmission of the corresponding frame and related frames is all completed. Here, the 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 related frames is all completed and before other contention window periods start operating. Here, the related frames include not only subsequent frames of the corresponding frame but also response (ACK) frames corresponding to each transmitted frame, etc. Thus, the length information indicated by LEN-2 is referred to as "overall transmission length information" in the embodiments of the present invention. According to one embodiment, LEN-2 may indicate the information of the duration field of the corresponding frame, or may indicate the length information of the TXOP guaranteed to the terminal transmitting the corresponding frame. Finally, LEN-3 displays any length information defined by the MAC.

[0175] On the other hand, the information indicated by LEN-1 and LEN-2 is not limited to that described above and may be modified in other ways. That is, in the embodiments of the present invention, at least one of LEN-1 and LEN-2 indicates the overall transmission length information. If LEN-1 indicates length information (for example, overall 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 (for example, overall 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 having data to be transmitted receives non-legacy wireless LAN information having a BSS identifier information different from that of the corresponding terminal (i.e., a non-legacy wireless LAN signal of another BSS), the terminal performs channel access based on the CCA procedure according to the above-described embodiment. At this time, according to an embodiment of the present invention, the terminal adjusts the data transmission period of the corresponding terminal by using at least one of the LEN-1, LEN-2, and LEN-3 information of the received non-legacy wireless LAN signal of another BSS. If the terminal transmits a single frame, the data transmission period means the duration of the corresponding frame, and if the terminal transmits a plurality of frames continuously, the data transmission period means the TXOP of the corresponding terminal. Specific embodiments thereof will be described with reference to FIGS. 21 to 23.

[0177] First, FIG. 21 is a diagram showing an embodiment of adjusting the data transmission period of a terminal based on the length information of a received wireless LAN signal. Referring to FIG. 21, a terminal OT of an OBSS transmits data (O_DATA) to a terminal OR, and the terminal OR transmits a response message (O_ACK) to the terminal OT in response to the received data (O_DATA). When the terminal MT transmits data (MY_DATA) while the O_DATA is being transmitted, the terminal MT extracts the 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). At this time, 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 FIG. 21, LEN-1 indicates the length information of O_DATA, and LEN-2 indicates the entire transmission length information of O_DATA+SIFS+O_ACK.

[0178] According to the embodiment of FIG. 21, based on the length information LEN_(O_DATA) extracted from O_DATA, the terminal MT adjusts so that the transmission period of MY_DATA transmitted by the corresponding terminal ends at the same time as or prior to the completion time of the transmission of the wireless signal O_DATA. That is, the terminal MT adjusts the length of MY_DATA transmitted by the corresponding terminal to be less than or equal to LEN(O_DATA). The wireless LAN 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 MY_DATA in various ways. For example, when the PPDU is composed of terminal MPDUs, the terminal MT performs fragmentation on the corresponding MPDU based on the extracted length information to reduce the length of MY_DATA. Also, when the PPDU is composed of an A-MPDU, the terminal MT limits the number of MPDUs included in the A-MPDU based on the extracted length information or performs fragmentation on individual MPDUs to reduce the length of MY_DATA. According to one embodiment, when adjusting the length of MY_DATA, the terminal MT refers to the LLE information and / or HLE information of O_DATA.

[0179] On the other hand, in the embodiment of FIG. 21, when the transmission period of MY_DATA ends at the same time as the completion time of the transmission of O_DATA, the response message (MY_ACK) of the terminal MR and the response message (O_ACK) of the terminal OR are transmitted simultaneously. However, when MY_ACK and O_ACK are received by the legacy terminal L at the same time, the legacy terminal L recognizes that a collision 830 between the data occurs. Therefore, after the transmission of the response messages (MY_ACK, O_ACK) is completed, there is a problem that the legacy terminal L approaches the channel after an EIFS (Extended Inter Frame Spacing) longer than the AIFS.

[0180] Next, FIG. 22 is a diagram showing another embodiment of adjusting the data transmission period of a terminal based on the length information of the received wireless LAN signal. In the embodiment of FIG. 22, the same or corresponding parts as those in the embodiment of FIG. 21 described above are omitted from the overlapping description.

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

[0182] On the other hand, the terminal MT, the terminal MR, or other terminals in MYBSS may attempt data transmission while O_ACK is being transmitted. According to an embodiment, arbitrary information is inserted into a preset specific message, such as RTS, CTS, and ACK messages, etc., and when a message containing the corresponding information is received, the adjustment of the CCA threshold according to the above-described embodiment may not be allowed. That is, the terminals of other BSSs that receive the message perform channel access based on the first CCA threshold CCA-SD1 instead of the second CCA threshold CCA-SD2.

[0183] Thus, according to the embodiment of FIG. 22, all terminals including legacy terminals will attempt channel access if the channel is idle during the time of AIFS after the O_ACK transmission of the terminal OR is completed. Therefore, an equitable access opportunity between non-legacy terminals and legacy terminals is guaranteed.

[0184] FIG. 23 is a diagram showing another embodiment of adjusting the data transmission period of a terminal based on the length information of a received wireless LAN signal. In the embodiment of FIG. 23, the same or corresponding parts of the embodiments of FIGS. 21 to 22 described above are omitted from the overlapping description.

[0185] According to the embodiment of FIG. 23, the terminal OT in the OBSS continuously transmits a plurality of data (O_DATA-1, O_DATA-2, O_DATA-3) during the TXOP interval (OT_TXOP) assigned to the corresponding terminal. In the case of a QoS (Quality of Service) terminal that transmits video data, voice data, etc., a plurality of data including at least one sub-sequent frame are continuously transmitted during the TXOP interval assigned to the corresponding terminal. Also, the terminal OR that receives 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 such a plurality of data and the corresponding response messages is completed within the TXOP interval (OT_TXOP) assigned to the terminal OT.

[0186] Thus, 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. At this time, 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 data of the terminal, the data transmission period means the duration of the corresponding data frame, and if the terminal MT continuously transmits a plurality of data, the data transmission period means the TXOP of the corresponding terminal.

[0187] As in the embodiment of FIG. 23, when the terminal MT transmits data during the transmission of O_DATA-1, the terminal MT extracts the length information LEN(O_DATA-1) from O_DATA-1, and adjusts the data transmission period of the corresponding terminal MT based on the extracted length information LEN(O_DATA-1). At this time, the length information LEN(O_DATA-1) extracted 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 is extracted, and LEN-2 indicates the TXOP interval (OT_TXOP) assigned to the terminal OT that transmits the corresponding data O_DATA-1, that is, the length of (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 the MAC.

[0188] As described above, the information indicated by LEN-1 and LEN-2 is not limited to this, and may be modified by other methods. For example, LEN-1 may indicate the length of the TXOP interval (OT_TXOP) assigned to the terminal OT that transmits the corresponding data O_DATA-1. If LEN-1 indicates length information (for example, overall 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 (for example, overall 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 FIG. 23, the terminal MT adjusts the data transmission period of the terminal MT to end before the data transmission completion time of the terminal OT based on the extracted length information LEN(O_DATA-1). As in the embodiment of FIG. 23, when the terminal transmits a plurality of data continuously, the length of the TXOP interval (MT_TXOP) assigned to the terminal MT, that is, (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 shorter than the length of the TXOP interval (OT_TXOP) assigned to the terminal OT. More specifically, referring to FIG. 23, the length of the TXOP interval (MT_TXOP) assigned to the terminal MT is set to be equal to or less than OT_TXOP-LEN(O-ACK)-SIFS. That is, the terminal MT adjusts so that the total length of one or more data transmitted by the corresponding terminal 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, respectively.

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

[0191] As described above, according to the embodiments of the present invention, the terminal MT determines the data transmission period of the corresponding terminal by using the 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 during a short time before decoding the MAC header of O_DATA.

[0192] FIG. 24 is a diagram showing still another embodiment for solving the inequality problem of legacy terminals that may occur when the CCA threshold adjusted according to the embodiments 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 each represent a non-legacy terminal, and Leg and Leg X each represent a legacy terminal. Also, in the first BSS operated by HE A, terminals HE1, HE2, HE3, and Leg X are associated, and in the second BSS operated by HE B, terminals HE, HE0, and Leg are associated.

[0193] In the embodiment of FIG. 24, when the terminal HE0 in the second BSS transmits data, the signal of the corresponding data is sensed by the terminals in the adjacent first BSS. When the wireless signals of other BSSs are sensed in this way, the non-legacy terminals HE1, HE2, and HE3 in the first BSS perform CCA based on the second CCA threshold CCA-SD2 described above, and the legacy terminal Leg X performs CCA based on the first CCA threshold CCA-SD1. Assuming that the data of the terminal HE0 is received by each terminal at a received signal strength between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, the non-legacy terminals HE1, HE2, and HE3 each perform a backoff procedure while decreasing the backoff counter (backoff1, backoff2, backoff3) assigned to the corresponding terminal, but the legacy terminal Leg X cannot perform the backoff procedure and defers channel access, etc., resulting in an inequality problem.

[0194] In addition, when the data transmission of terminals HE0 and HE1 is completed and the channel becomes idle, non-legacy terminals HE2 and HE3 resume the backoff procedure using the remaining backoff counters (remainig backoff2, remainig backoff3) left in the previous backoff procedure respectively. However, since terminal Leg X was unable to decrement the backoff counter during the previous backoff procedure of the non-legacy terminals, it resumes the backoff procedure using the backoff counter (backoff X) conventionally assigned to the corresponding terminal. Therefore, even in subsequent contention window periods, the probability of the legacy terminal accessing the channel is reduced compared to that of the non-legacy terminal.

[0195] To solve such problems, according to an embodiment of the present invention, by adjusting the backoff counter used in the backoff procedure of non-legacy terminals in the spatial reuse section, the balance of channel access between non-legacy terminals and legacy terminals can be maintained. The spatial reuse section in the present invention refers to a section where channel access is performed based on an adjusted CCA threshold when the BSS identifier information of the received radio signal is different from the BSS identifier information of the terminal.

[0196] In the spatial reuse section, non-legacy terminals HE1, HE2, and HE3 of the first BSS perform CCA based on the second CCA threshold CCA-SD2. As a result of performing the CCA, if the corresponding channel is determined to be idle, the non-legacy terminals perform the backoff procedure using the backoff counters assigned to each terminal. In the embodiment of FIG. 24, during the backoff procedure, the terminal HE1 whose backoff counter expires first transmits data. At this time, the backoff procedures of the remaining terminals HE2 and HE3 are interrupted.

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

[0198] On the other hand, according to another embodiment of the present invention, the non-legacy terminal performs channel access using a plurality of backoff counters. For example, the non-legacy terminal is assigned a first backoff counter and a second backoff counter for the backoff procedure. At this time, 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 radio signal. For example, if the received signal strength of a radio signal having BSS identifier information different from the corresponding terminal is lower than a first CCA threshold CCA-SD1, the non-legacy terminal consumes the backoff counter, and if the received signal strength of the radio signal is between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, the non-legacy terminal consumes the second backoff counter. The non-legacy terminal transmits data when at least one of the first backoff counter and the second backoff counter expires.

[0199] Thus, the non-legacy terminal according to the embodiment of FIG. 24 can minimize the inequality that may occur in the legacy terminal by adjusting the backoff counter used in the backoff procedure in the spatial reuse section or performing the backoff procedure using a plurality of backoff counters.

[0200] FIG. 25 is a diagram showing interference problems that may occur when the 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 indicate a transmission terminal and a reception terminal of a first BSS (MYBSS), and OT and OR indicate a transmission terminal and a reception terminal of another second BSS (OBSSS) different from this.

[0201] As shown in FIG. 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). On the other hand, the terminal MT of the MYBSS, which is a BSS different from the OBSS, determines whether the channel can be occupied based on the reception signal strength of the wireless signal O_DATA and the BSS identifier information of the corresponding signal as in the above-described embodiment. That is, when the BSS identifier information of the received wireless signal O_DATA is different from the BSS identifier information of the corresponding terminal, the terminal MT performs CCA based on the above-described second CCA threshold CCA-SD2. At this time, the second CCA threshold has a higher level than the first CCA threshold used in the legacy terminal.

[0202] If the reception signal strength of O_DATA is lower than the second CCA threshold, the terminal MT determines that the corresponding channel is in an idle state 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 that has received MY_DATA from the terminal MT transmits a response message (MY_ACK) in response thereto.

[0203] However, since whether the terminal MT can access the channel is determined based on the reception signal strength of O_DATA transmitted by the terminal OT, the MY_DATA transmitted by the terminal MT causes interference to the terminal OR of the OBSS. Such a problem can occur not only during single MPDU transmission but also in a transmission situation based on TXOP or A-MPDU.

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

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

[0206] According to the embodiments of the present invention, when the terminal MT of the MYBSS receives a request message (O_REQ) having BSS identifier information different from that of the corresponding terminal and a response message (O_RSP) corresponding thereto, it determines whether it is possible to approach the channel, that is, whether it is possible to transmit the data (MY_DATA) of the corresponding terminal, based on the received signal strengths of O_REQ and O_RSP. At this time, the terminal MT determines whether it is possible to transmit MY_DATA based on the result of comparing the received signal strengths of O_REQ and O_RSP with the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2 described above. 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 perform data transmission according to other 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 both lower than the threshold CCA-SD1 of the first CCA, 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, if 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 influence of the interference 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. Thus, when the BSS identifier information of the received radio signal is different from the BSS identifier information of the terminal, the section in which channel approach is performed based on the adjusted CCA threshold is referred to as a spatial reuse section in the present invention.

[0209] According to an embodiment of the present invention, a terminal MT that transmits data in a spatial reuse space can transmit data immediately without exchanging separate request messages and response messages. Also, the terminal MT continuously measures the received signal strength of data transmitted by an OBSS terminal in the spatial reuse space, and adjusts the channel accessibility in real time based on the measured results. At this time, the same criteria as O_REQ are applied to the data (O_DATA-1, O_DATA-2) transmitted by the OBSS terminal OT, and the same criteria as O_RSP are applied to the data (O_ACK-1, O_ACK-2) transmitted by the terminal OR. If the received signal strength of the data transmitted by the OBSS terminal belongs to 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 the data transmitted by the OBSS terminal belongs to a different signal strength interval from the received signal strength of the corresponding O_REQ or O_RSP, the terminal MT re-determines the channel accessibility based on the received signal strength of the received data. Here, the received signal strength interval includes a first interval lower than the first CCA threshold CCA-SD1, a second interval between the first CCA threshold CCA-SD1 and the second CCA threshold CCA-SD2, and a third interval higher than the second CCA threshold CCA-SD2.

[0210] If O_REQ and O_RSP include the length information according to the above-described embodiment, the terminal MT that receives this extracts the length information from the corresponding message and adjusts the data transmission period of the corresponding terminal MT based on this. 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, FIG. 27 is a diagram showing an additional embodiment for minimizing the interference on the terminal MR of MYBSS. In the embodiment of FIG. 27, the same or corresponding parts as those in the embodiment of FIG. 26 described above are omitted from the overlapping description.

[0212] As described in the embodiment of FIG. 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 it is possible to access the channel based on the received signal strengths of O_REQ and O_RSP. According to the embodiment of FIG. 27, when it is determined that the terminal MT approaches the channel, the terminal MT transmits a request message (MY_REQ) to the receiving terminal MR. The MY_REQ is a message indicating that data transmission of the terminal MT is possible, and is implemented by RTS, NDP, or a single MPDU, etc.

[0213] The terminal MR that receives the MY_REQ from the terminal MT determines whether to receive the data (MY_DATA) of the terminal MT based on the received signal strengths of O_REQ and O_RSP. At this time, the terminal MR determines whether it is possible to receive MY_DATA based on the result of comparing the received signal strengths of O_REQ and O_RSP with the above-mentioned first CCA threshold CCA-SD1 and 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 when 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 MR cannot receive MY_DATA. However, in this case, the terminal MR may exceptionally receive data according to 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 both 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 _RSP is lower than the second CCA threshold CCA-SD2, if the received signal strength of O_REQ is lower than the first CCA threshold CCA-SD1, the terminal MR can receive MY_DATA. In this case, it is presumed that the influence of the interference on MR caused by the O_DATA transmitted by the OBSS terminal OT is small. Therefore, the terminal MR can successfully receive the data (MY_DATA-1, MY_DATA-2) transmitted by the terminal MT.

[0216] Based on whether the terminal MR can receive the determined MY_DATA, the terminal MR transmits a response message (MY_RSP) corresponding to the MY_REQ transmitted by the terminal MT. The MY_RSP is a message indicating that the data of the terminal MT can be received, and is embodied by CTS or ACK, etc. 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 MY_RSP is received 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 MY_RSP is not received from the terminal MR, the terminal MT cannot transmit MY_DATA. Thus, according to the embodiment of FIG. 27, by exchanging MY_REQ and MY_RSP between the terminals of MYBSS in the spatial reuse interval, it is possible to additionally determine whether the terminal MR can receive the data (MY_DATA) of the terminal MT without being interfered.

[0217] FIG. 28 and FIG. 29 are diagrams showing still other interference problems that may occur when the CCA threshold adjusted according to the embodiment of the present invention is used for channel access. In the embodiments of FIGS. 28 and 29, the same or corresponding parts as those in the embodiment of FIG. 25 are omitted from the repeated description.

[0218] As shown in FIGS. 28 and 29, in 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). On the other hand, terminal MT of MYBSS, which is a BSS different from OBSS, determines whether it can occupy the channel and approaches the channel according to the above-described embodiments. That is, terminal MT performs a backoff procedure and transmits data (MY_DATA) when the backoff counter in the backoff procedure expires. Further, terminal MR that has received MY_DATA from terminal MT transmits a response message (MY_ACK) in response thereto.

[0219] However, MY_ACK transmitted by terminal MR may interfere with the terminals in OBSS. Referring to FIG. 28, MY_ACK transmitted by terminal MR interferes with terminal OR receiving the data (O_DATA) of terminal OT. Further, referring to FIG. 29, MY_ACK transmitted by terminal MR may also interfere with terminal OT receiving the response message (O_ACK) of terminal OR.

[0220] FIG. 30 is a diagram showing still another embodiment showing a data transmission method of non-legacy terminals for minimizing the interference problem between terminals. In the embodiment of FIG. 30, the same or corresponding parts as those in the embodiments of FIGS. 26 and 27 are not described repeatedly.

[0221] As shown in the figure, when the OBSS terminal transmits O_REQ and O_RSP, the terminals MT and MR of MYBSS can receive them. As in the above-described embodiment, the terminal MT of MYBSS determines whether the channel is accessible based on the received signal strengths of O_REQ and O_RSP, and transmits data (MY_DATA). Also, 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 timing of MY_ACK based on the received signal strengths of O_REQ and O_RSP. At this time, the terminal MR determines the transmission timing of MY_ACK based on the result of comparing the received signal strengths of O_REQ and O_RSP with the above-described first CCA threshold value CCA-SD1 and second CCA threshold value CCA-SD2. Here, the second CCA threshold value CCA-SD2 has a higher level than the first CCA threshold value CCA-SD1.

[0222] First, if the received signal strength of O_REQ is between the first CCA threshold value CCA-SD1 and the second CCA threshold value CCA-SD2, and the received signal strength of O_RSP is lower than the first CCA threshold value CCA-SD1, the terminal MR transmits MY_ACK841 within the transmission period of the data (O_DATA) of the terminal OT. In this case, it is presumed that the influence of the interference that MY_ACK841 transmitted by the terminal MR has 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 value CCA-SD1 and the second CCA threshold value CCA-SD2, and the received signal strength of O_REQ is lower than the first CCA threshold value CCA-SD1, the terminal MR transmits MY_ACK842 together with the transmission of the terminal OR response message (O_ACK). In this case, it is presumed that the influence of the interference that MY_ACK842 transmitted by the terminal MR has on the OBSS terminal OT is small. Therefore, the terminal OT can successfully receive the O_ACK transmitted by the terminal OR.

[0224] Next, if the received signal strengths of all of O_REQ and O_RSP are higher than the second CCA threshold CCA-SD2, after the transmission of the terminal OT data (O_DATA) and the transmission of the response message (O_ACK) of the terminal OR are completed, the terminal MR transmits MY_ACK843. In this case, it is estimated that the MY_ACK843 transmitted by the terminal MR interferes with the OBSS terminals OT and OR. Therefore, the terminal MR can prevent data collisions that may occur in the OBSS terminal by transmitting MY_ACK843 after the data exchange between the terminal OT and OR is completed.

[0225] According to an additional 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, the received signal strength of MY_DATA, and the like. Through this, the terminal MR can minimize the amount of interference that MY_ACK causes to the terminal OT or the terminal OR.

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

[0227] The embodiments of the present invention described above are implemented through various means. For example, the embodiments of the present invention are implemented by hardware, firmware, software, or a combination thereof.

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

[0229] In the case of implementation by firmware or software, the method according to an embodiment of the present invention is implemented in the form of modules, procedures, functions, etc. that perform the functions or operations described above. The software code is stored in a memory and executed by a processor. The memory is located inside or outside the processor and exchanges data with the processor by various means already known.

[0230] The above description of the present invention is for illustrative purposes, and those with ordinary knowledge in the technical field to which the present invention pertains should be able to understand that it can be easily changed to other specific forms without changing the technical idea or essential features of the present invention. Therefore, the embodiments described so far should be analyzed as being exemplary and limiting in all aspects. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as being distributed may also be implemented in a combined form.

[0231] The scope of the present invention is indicated by the claims described later rather than the above detailed description, and it should be analyzed that all changes or modified forms derived from the meaning and scope of the claims and the equivalent concept thereof are included in the scope of the present invention.

Industrial Applicability

[0232] Although various embodiments of the present invention have been described mainly with respect to IEEE 802.11 systems, they are applicable to various other forms of mobile communication devices, mobile communication systems, and the like.

Claims

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 unit; The processor, receiving a first packet including BSS (Basic Service Set) identifier information via the transceiver unit; transmitting a second packet based on the first packet; a second duration associated with the transmission of the second packet is limited to end simultaneously with or prior to a completion time of the transmission of the first packet based on the first duration associated with the first packet when the BSS identifier information indicates a specific BSS other than the BSS of the wireless communication terminal; Wireless communication terminal.

2. The BSS identifier information is used to identify whether the first packet is transmitted from the specific BSS different from the BSS of the wireless communication terminal.

2. The wireless communication terminal according to claim 1.

3. The processor, measuring a signal strength of the first packet; and determining whether a particular channel over which the first packet is to be transmitted is occupied based on the signal strength and the BSS identifier information.

2. The wireless communication terminal according to claim 1.

4. The determination of whether the specific channel is occupied or not is made based on a CCA (Clear Channel Assessment) for the specific channel, and a CCA threshold value for the CCA is set to a different level depending on whether the BSS identifier information of the first packet is the same as the BSS identifier information of the wireless communication terminal.

4. The wireless communication terminal according to claim 3.

5. The second duration represents a TXOP (Transmission Opportunity) of the wireless communication terminal.

2. The wireless communication terminal according to claim 1.

6. The information of the TXOP of the wireless communication terminal is included in a non-legacy preamble of the second packet.

6. The wireless communication terminal according to claim 5.

7. A wireless communication method for a wireless communication terminal, comprising: receiving a first packet including BSS (Basic Service Set) identifier information via a transceiver; transmitting a second packet based on the first packet; a second duration associated with the transmission of the second packet is limited to end simultaneously with or prior to a completion time of the transmission of the first packet based on the first duration associated with the first packet when the BSS identifier information indicates a specific BSS other than the BSS of the wireless communication terminal; A wireless communication method.

8. The BSS identifier information is used to identify whether the first packet is transmitted from the specific BSS different from the BSS of the wireless communication terminal. The wireless communication method according to claim 7.

9. A step of measuring a signal strength of the first packet; determining whether a particular channel through which the first packet is transmitted is occupied based on the signal strength and the BSS identifier information.

8. The wireless communication terminal according to claim 7.

10. The step of determining whether the specific channel is occupied or not is performed based on a CCA (Clear Channel Assessment) for the specific channel, and a CCA threshold value for the CCA is set to a different level depending on whether the BSS identifier information of the first packet is the same as the BSS identifier information of the wireless communication terminal. The wireless communication method according to claim 9.

11. The second duration represents a transmission opportunity (TXOP) of the wireless communication terminal. The wireless communication method according to claim 7.

12. The information of the TXOP of the wireless communication terminal is included in a non-legacy preamble of the second packet. The wireless communication method according to claim 11.

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