WO2014092450A1 - 무선랜 시스템에서 제한된 액세스 윈도우 기반 채널 액세스 방법 및 장치 - Google Patents
무선랜 시스템에서 제한된 액세스 윈도우 기반 채널 액세스 방법 및 장치 Download PDFInfo
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Definitions
- the following description relates to a wireless communication system, and more particularly, to a method and apparatus for accessing a channel based on a restricted access window in a WLAN system.
- WLAN is based on radio frequency technology, and can be used in homes, businesses, or businesses by using portable terminals such as personal digital assistants (PDAs), laptop computers, and portable multimedia players (PMPs). It is a technology that allows wireless access to the Internet in a specific service area.
- PDAs personal digital assistants
- PMPs portable multimedia players
- IEEE 802.11n supports High Throughput (HT) with data throughput up to 540 Mbps or more, and also uses multiple antennas at both the transmitter and receiver to minimize transmission errors and optimize data rates.
- HT High Throughput
- MIMO Multiple Inputs and Multiple Outputs
- IEEE 802.11 WLAN system a technical standard for supporting M2M communication is being developed as IEEE 802.11ah.
- M2M communications you may want to consider a scenario where you occasionally communicate a small amount of data at low speeds in an environment with many devices.
- Communication in a WLAN system is performed in a medium shared between all devices.
- M2M communication spending a large amount of time for channel access of one device may not only reduce the overall system performance, but also prevent power saving of each device.
- RAW restricted access windows
- An object of the present invention is to provide a method for setting whether to allow channel access related to a RAW boundary when RAW is allocated.
- a method of performing a channel access by a station (STA) in a wireless communication system when a limited access window (RAW) is assigned to the STA, an access point Receiving RAW cross boundary transmission permission (CBTA) information from the (AP); And performing transmission from the STA based on the RAW CBTA information.
- RAW CBTA information is set to the first value, transmission of the STA that crosses the boundary of the RAW may be allowed.
- an access point supports a channel access of a station (STA), and a limited access window (RAW) for the STA If is assigned, may include transmitting RAW cross boundary transmission permission (CBTA) information to the STA.
- the transmission from the STA may be performed based on the RAW CBTA information.
- RAW CBTA information is set to the first value, transmission of the STA that crosses the boundary of the RAW may be allowed.
- a station (STA) apparatus for performing channel access in a wireless communication system according to another embodiment of the present invention, a transceiver; And a processor.
- the processor when the restricted access window (RAW) is allocated to the STA, receives RAW cross boundary transmission permission (CBTA) information from the access point (AP) using the transceiver;
- the transmission from the STA may be configured to be performed using the transceiver based on the RAW CBTA information.
- RAW CBTA information is set to the first value, transmission of the STA that crosses the boundary of the RAW may be allowed.
- an access point (AP) device supporting channel access of a station (STA) in a wireless communication system may include transmitting RAW cross boundary transmission permission (CBTA) information to the STA using the transceiver when a restricted access window (RAW) is allocated to the STA.
- RAW cross boundary transmission permission
- RAW restricted access window
- the RAW may be divided into one or more slots.
- the transmission from the STA may be performed based on the RAW CBTA information.
- the RAW CBTA information may be included in a RAW parameter set information element (RPS IE).
- RPS IE RAW parameter set information element
- the RPS IE may be received from the AP through a beacon frame.
- One or more RAW CBTA information may be received from the AP during the RAW.
- the one or more RAW CBTA information may be received from the AP through a null-data packet (NDP) frame or a control frame.
- NDP null-data packet
- the NDP frame may be a NDP-CTS (Clear To Send) frame or an NDP-ACK (Acknowledgment) frame.
- NDP-CTS Clear To Send
- NDP-ACK Acknowledgment
- the control frame may be a CTS frame or an ACK frame.
- the transmission from the STA may be performed based on the last received RAW CBTA information among the one or more RAW CBTA information.
- the RAW may be divided into one or more slots.
- the one or more RAW CBTA information may be transmitted after the start of the one or more slots or before the boundary of the RAW.
- a method and apparatus for setting whether to allow channel access related to a boundary of RAW when RAW is allocated may be provided.
- FIG. 1 is a diagram illustrating an exemplary structure of an IEEE 802.11 system to which the present invention can be applied.
- FIG. 2 is a diagram illustrating another exemplary structure of an IEEE 802.11 system to which the present invention can be applied.
- FIG. 3 is a diagram illustrating another exemplary structure of an IEEE 802.11 system to which the present invention can be applied.
- FIG. 4 is a diagram illustrating an exemplary structure of a WLAN system.
- FIG. 5 is a diagram illustrating a link setup process in a WLAN system.
- FIG. 6 is a diagram for describing a backoff process.
- 7 is a diagram for explaining hidden nodes and exposed nodes.
- FIG. 8 is a diagram for explaining an RTS and a CTS.
- FIG. 9 is a diagram for describing a power management operation.
- 10 to 12 are diagrams for explaining in detail the operation of the STA receiving the TIM.
- FIG. 13 is a diagram for explaining RAW allocation.
- FIGS. 14 to 19 are diagrams for explaining examples of a RAW allocation method according to the present invention.
- FIG. 20 illustrates a method of accessing a channel based on a restricted access window according to an embodiment of the present invention.
- 21 is a block diagram illustrating a configuration of a wireless device according to an embodiment of the present invention.
- each component or feature may be considered to be optional unless otherwise stated.
- Each component or feature may be embodied in a form that is not combined with other components or features.
- some components and / or features may be combined to form an embodiment of the present invention.
- the order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment.
- Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802 system, 3GPP system, 3GPP LTE and LTE-A (LTE-Advanced) system and 3GPP2 system. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.
- CDMA code division multiple access
- FDMA frequency division multiple access
- TDMA time division multiple access
- OFDMA orthogonal frequency division multiple access
- SC-FDMA single carrier frequency division multiple access
- CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000.
- TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE).
- GSM Global System for Mobile communications
- GPRS General Packet Radio Service
- EDGE Enhanced Data Rates for GSM Evolution
- OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA).
- Wi-Fi IEEE 802.11
- WiMAX IEEE 802.16
- E-UTRA Evolved UTRA
- FIG. 1 is a diagram showing an exemplary structure of an IEEE 802.11 system to which the present invention can be applied.
- the IEEE 802.11 architecture may be composed of a plurality of components, and by their interaction, a WLAN may be provided that supports transparent STA mobility for higher layers.
- the Basic Service Set (BSS) may correspond to a basic building block in an IEEE 802.11 LAN. 1 exemplarily shows that there are two BSSs (BSS1 and BSS2) and two STAs are included as members of each BSS (STA1 and STA2 are included in BSS1 and STA3 and STA4 are included in BSS2). do.
- an ellipse representing a BSS may be understood to represent a coverage area where STAs included in the BSS maintain communication. This area may be referred to as a basic service area (BSA).
- BSA basic service area
- the most basic type of BSS in an IEEE 802.11 LAN is an independent BSS (IBSS).
- the IBSS may have a minimal form consisting of only two STAs.
- the BSS (BSS1 or BSS2) of FIG. 1, which is the simplest form and other components are omitted, may correspond to a representative example of the IBSS.
- This configuration is possible when STAs can communicate directly.
- this type of LAN may not be configured in advance, but may be configured when a LAN is required, which may be referred to as an ad-hoc network.
- the membership of the STA in the BSS may be dynamically changed by turning the STA on or off, the STA entering or exiting the BSS region, and the like.
- the STA may join the BSS using a synchronization process.
- the STA In order to access all services of the BSS infrastructure, the STA must be associated with the BSS. This association may be set up dynamically and may include the use of a Distribution System Service (DSS).
- DSS Distribution System Service
- FIG. 2 is a diagram illustrating another exemplary structure of an IEEE 802.11 system to which the present invention can be applied.
- components such as a distribution system (DS), a distribution system medium (DSM), and an access point (AP) are added in the structure of FIG. 1.
- DS distribution system
- DSM distribution system medium
- AP access point
- the station-to-station distance directly in the LAN can be limited by PHY performance. In some cases, this distance limit may be sufficient, but in some cases, communication between more distant stations may be necessary.
- the distribution system DS may be configured to support extended coverage.
- the DS refers to a structure in which BSSs are interconnected. Specifically, instead of the BSS independently as shown in FIG. 1, the BSS may exist as an extended type component of a network composed of a plurality of BSSs.
- DS is a logical concept and can be specified by the nature of the distribution system medium (DSM).
- DSM distribution system medium
- the IEEE 802.11 standard logically distinguishes between wireless medium (WM) and distribution system media (DSM).
- Each logical medium is used for a different purpose and is used by different components.
- the definition of the IEEE 802.11 standard does not limit these media to the same or to different ones.
- the plurality of media logically different, the flexibility of the IEEE 802.11 LAN structure (DS structure or other network structure) can be described. That is, the IEEE 802.11 LAN structure can be implemented in various ways, the corresponding LAN structure can be specified independently by the physical characteristics of each implementation.
- the DS may support the mobile device by providing seamless integration of multiple BSSs and providing logical services for handling addresses to destinations.
- An AP means an entity that enables access to a DS through WM for associated STAs and has STA functionality. Data movement between the BSS and the DS may be performed through the AP.
- STA2 and STA3 shown in FIG. 2 have the functionality of a STA, and provide a function to allow associated STAs STA1 and STA4 to access the DS.
- all APs basically correspond to STAs, all APs are addressable entities. The address used by the AP for communication on the WM and the address used by the AP for communication on the DSM need not necessarily be the same.
- Data transmitted from one of the STAs associated with an AP to the STA address of that AP may always be received at an uncontrolled port and processed by an IEEE 802.1X port access entity.
- transmission data (or frame) may be transmitted to the DS.
- FIG. 3 is a diagram illustrating another exemplary structure of an IEEE 802.11 system to which the present invention can be applied. 3 conceptually illustrates an extended service set (ESS) for providing wide coverage in addition to the structure of FIG. 2.
- ESS extended service set
- a wireless network of arbitrary size and complexity may be composed of DS and BSSs.
- this type of network is called an ESS network.
- the ESS may correspond to a set of BSSs connected to one DS. However, the ESS does not include a DS.
- the ESS network is characterized by what appears to be an IBSS network at the LLC (Logical Link Control) layer. STAs included in the ESS can communicate with each other, and mobile STAs can move from within one BSS to another BSS (within the same ESS) transparently to the LLC.
- LLC Logical Link Control
- BSSs can be partially overlapped, which is a form commonly used to provide continuous coverage.
- the BSSs may not be physically connected, and logically there is no limit to the distance between the BSSs.
- the BSSs can be located at the same physical location, which can be used to provide redundancy.
- one (or more) IBSS or ESS networks may be physically present in the same space as one (or more than one) ESS network.
- the ad-hoc network is operating at the location of the ESS network, if IEEE 802.11 networks are physically overlapped by different organizations, or if two or more different access and security policies are required at the same location. It may correspond to an ESS network type in a case.
- FIG. 4 is a diagram illustrating an exemplary structure of a WLAN system.
- an example of an infrastructure BSS including a DS is shown.
- BSS1 and BSS2 constitute an ESS.
- an STA is a device that operates according to MAC / PHY regulations of IEEE 802.11.
- the STA includes an AP STA and a non-AP STA.
- Non-AP STAs are devices that users typically handle, such as laptop computers and mobile phones.
- STA1, STA3, and STA4 correspond to non-AP STAs
- STA2 and STA5 correspond to AP STAs.
- a non-AP STA includes a terminal, a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), and a mobile terminal. May be referred to as a Mobile Subscriber Station (MSS).
- the AP may include a base station (BS), a node-B, an evolved Node-B (eNB), and a base transceiver system (BTS) in other wireless communication fields.
- BS base station
- eNB evolved Node-B
- BTS base transceiver system
- FIG. 5 is a diagram illustrating a general link setup process.
- an STA In order for an STA to set up a link and transmit / receive data with respect to a network, an STA first discovers the network, performs authentication, establishes an association, and authenticates for security. It must go through the back.
- the link setup process may also be referred to as session initiation process and session setup process.
- a process of discovery, authentication, association, and security establishment of a link setup process may be collectively referred to as association process.
- the STA may perform a network discovery operation.
- the network discovery operation may include a scanning operation of the STA. That is, in order for the STA to access the network, the STA must find a network that can participate. The STA must identify a compatible network before joining the wireless network. A network identification process existing in a specific area is called scanning.
- the STA performing scanning transmits a probe request frame and waits for a response to discover which AP exists in the vicinity while moving channels.
- the responder transmits a probe response frame to the STA that transmits the probe request frame in response to the probe request frame.
- the responder may be an STA that last transmitted a beacon frame in the BSS of the channel being scanned.
- the AP transmits a beacon frame, so the AP becomes a responder.
- the responder is not constant.
- an STA that transmits a probe request frame on channel 1 and receives a probe response frame on channel 1 stores the BSS-related information included in the received probe response frame and stores the next channel (eg, number 2).
- Channel to perform scanning (i.e., probe request / response transmission and reception on channel 2) in the same manner.
- the scanning operation may be performed by a passive scanning method.
- passive scanning the STA performing scanning waits for a beacon frame while moving channels.
- the beacon frame is one of management frames in IEEE 802.11.
- the beacon frame is notified of the existence of a wireless network and is periodically transmitted to allow the STA performing scanning to find the wireless network and participate in the wireless network.
- the AP periodically transmits a beacon frame
- the IBSS STAs in the IBSS rotate and transmit a beacon frame.
- the STA that performs the scanning receives the beacon frame, the STA stores the information on the BSS included in the beacon frame and records beacon frame information in each channel while moving to another channel.
- the STA may store BSS related information included in the received beacon frame, move to the next channel, and perform scanning on the next channel in the same manner.
- active scanning has the advantage of less delay and power consumption than passive scanning.
- step S520 After the STA discovers the network, an authentication process may be performed in step S520.
- This authentication process may be referred to as a first authentication process in order to clearly distinguish from the security setup operation of step S540 described later.
- the authentication process includes a process in which the STA transmits an authentication request frame to the AP, and in response thereto, the AP transmits an authentication response frame to the STA.
- An authentication frame used for authentication request / response corresponds to a management frame.
- the authentication frame includes an authentication algorithm number, an authentication transaction sequence number, a status code, a challenge text, a Robust Security Network, and a finite cyclic group. Group) and the like. This corresponds to some examples of information that may be included in the authentication request / response frame, and may be replaced with other information or further include additional information.
- the STA may send an authentication request frame to the AP.
- the AP may determine whether to allow authentication for the corresponding STA based on the information included in the received authentication request frame.
- the AP may provide a result of the authentication process to the STA through an authentication response frame.
- the association process includes a process in which the STA transmits an association request frame to the AP, and in response thereto, the AP transmits an association response frame to the STA.
- the association request frame may include information related to various capabilities, beacon listening interval, service set identifier (SSID), supported rates, supported channels, RSN, mobility domain. Information about supported operating classes, TIM Broadcast Indication Map Broadcast request, interworking service capability, and the like.
- an association response frame may include information related to various capabilities, status codes, association IDs (AIDs), support rates, Enhanced Distributed Channel Access (EDCA) parameter sets, Received Channel Power Indicators (RCPI), Received Signal to Noise Information, such as an indicator, a mobility domain, a timeout interval (association comeback time), an overlapping BSS scan parameter, a TIM broadcast response, and a QoS map.
- AIDs association IDs
- EDCA Enhanced Distributed Channel Access
- RCPI Received Channel Power Indicators
- Received Signal to Noise Information such as an indicator, a mobility domain, a timeout interval (association comeback time), an overlapping BSS scan parameter, a TIM broadcast response, and a QoS map.
- a security setup process may be performed at step S540.
- the security setup process of step S540 may be referred to as an authentication process through a Robust Security Network Association (RSNA) request / response.
- the authentication process of step S520 is called a first authentication process, and the security setup process of step S540 is performed. It may also be referred to simply as the authentication process.
- RSNA Robust Security Network Association
- the security setup process of step S540 may include, for example, performing a private key setup through 4-way handshaking through an Extensible Authentication Protocol over LAN (EAPOL) frame. .
- the security setup process may be performed according to a security scheme not defined in the IEEE 802.11 standard.
- IEEE 802.11n In order to overcome the limitation of communication speed in WLAN, IEEE 802.11n exists as a relatively recently established technical standard. IEEE 802.11n aims to increase the speed and reliability of networks and to extend the operating range of wireless networks. More specifically, IEEE 802.11n supports High Throughput (HT) with data throughput of up to 540 Mbps and also uses multiple antennas at both the transmitter and receiver to minimize transmission errors and optimize data rates. It is based on Multiple Inputs and Multiple Outputs (MIMO) technology.
- HT High Throughput
- MIMO Multiple Inputs and Multiple Outputs
- the next generation WLAN system supporting Very High Throughput is the next version of the IEEE 802.11n WLAN system (e.g., IEEE 802.11ac), which is 1 Gbps at the MAC Service Access Point (SAP).
- IEEE 802.11ac the next version of the IEEE 802.11n WLAN system
- SAP MAC Service Access Point
- the next generation WLAN system supports MU-MIMO (Multi User Multiple Input Multiple Output) transmission in which a plurality of STAs simultaneously access a channel in order to use the wireless channel efficiently.
- MU-MIMO Multi User Multiple Input Multiple Output
- the AP may simultaneously transmit packets to one or more STAs that are paired with MIMO.
- whitespace may be referred to as a licensed band that can be preferentially used by a licensed user.
- An authorized user refers to a user who is authorized to use an authorized band and may also be referred to as a licensed device, a primary user, an incumbent user, or the like.
- an AP and / or STA operating in a WS should provide protection for an authorized user. For example, if an authorized user such as a microphone is already using a specific WS channel, which is a frequency band divided in a regulation to have a specific bandwidth in the WS band, the AP may be protected. And / or the STA cannot use a frequency band corresponding to the corresponding WS channel. In addition, the AP and / or STA should stop using the frequency band when the authorized user uses the frequency band currently used for frame transmission and / or reception.
- the AP and / or STA should be preceded by a procedure for determining whether a specific frequency band in the WS band is available, that is, whether there is an authorized user in the frequency band. Knowing whether there is an authorized user in a specific frequency band is called spectrum sensing. As the spectrum sensing mechanism, energy detection, signal detection, and the like are used. If the strength of the received signal is greater than or equal to a predetermined value, it may be determined that the authorized user is in use, or if the DTV preamble is detected, the authorized user may be determined to be in use.
- M2M communication refers to a communication method that includes one or more machines (Machine), may also be referred to as MTC (Machine Type Communication) or thing communication.
- a machine refers to an entity that does not require human direct manipulation or intervention.
- a device such as a meter or a vending machine equipped with a wireless communication module, as well as a user device such as a smartphone that can automatically connect and communicate with a network without a user's operation / intervention, may be used. This may correspond to an example.
- the M2M communication may include communication between devices (eg, device-to-device (D2D) communication), communication between a device, and an application server.
- D2D device-to-device
- Examples of device and server communication include communication between vending machines and servers, point of sale devices and servers, and electricity, gas or water meter readers and servers.
- applications based on M2M communication may include security, transportation, health care, and the like. Considering the nature of these applications, M2M communication should generally be able to support the transmission and reception of small amounts of data at low speeds in the presence of very many devices.
- M2M communication should be able to support a large number of STAs.
- WLAN system it is assumed that a maximum of 2007 STAs are associated with one AP, but in M2M communication, there are methods for supporting a case where a larger number (approximately 6000 STAs) are associated with one AP. Is being discussed.
- many applications are expected to support / require low data rates in M2M communication.
- an STA may recognize whether data to be transmitted to it is based on a TIM (Traffic Indication Map) element, and methods for reducing the bitmap size of the TIM are discussed. It is becoming.
- TIM Traffic Indication Map
- M2M communication is expected to be a lot of traffic with a very long transmission / reception interval. For example, very small amounts of data are required to be sent and received every long period (eg, one month), such as electricity / gas / water use. Accordingly, in the WLAN system, even if the number of STAs that can be associated with one AP becomes very large, it is possible to efficiently support the case where the number of STAs having data frames to be received from the AP is very small during one beacon period. The ways to do this are discussed.
- WLAN technology is rapidly evolving and, in addition to the above examples, technologies for direct link setup, media streaming performance improvement, support for high speed and / or large initial session setup, support for extended bandwidth and operating frequency, etc. Is being developed.
- a basic access mechanism of MAC is a carrier sense multiple access with collision avoidance (CSMA / CA) mechanism.
- the CSMA / CA mechanism is also called the Distributed Coordination Function (DCF) of the IEEE 802.11 MAC. It basically employs a "listen before talk" access mechanism.
- the AP and / or STA may sense a radio channel or medium during a predetermined time period (e.g., during a DCF Inter-Frame Space (DIFS), before starting transmission.
- DIFS DCF Inter-Frame Space
- a delay period for example, a random backoff period
- HCF hybrid coordination function
- the PCF refers to a polling-based synchronous access scheme in which polling is performed periodically so that all receiving APs and / or STAs can receive data frames.
- the HCF has an Enhanced Distributed Channel Access (EDCA) and an HCF Controlled Channel Access (HCCA).
- EDCA is a competition based approach for providers to provide data frames to multiple users, and HCCA uses a non-competition based channel access scheme using a polling mechanism.
- the HCF includes a media access mechanism for improving the quality of service (QoS) of the WLAN, and can transmit QoS data in both a contention period (CP) and a contention free period (CFP).
- QoS quality of service
- FIG. 6 is a diagram for describing a backoff process.
- the random backoff count has a pseudo-random integer value and may be determined to be one of values in the range of 0 to CW.
- CW is a contention window parameter value.
- the CW parameter is given CWmin as an initial value, but may take a double value in case of transmission failure (eg, when an ACK for a transmitted frame is not received).
- the STA continues to monitor the medium while counting down the backoff slots according to the determined backoff count value. If the medium is monitored as occupied, the countdown stops and waits; if the medium is idle, it resumes the remaining countdown.
- the STA3 may confirm that the medium is idle as much as DIFS and transmit the frame immediately. Meanwhile, the remaining STAs monitor and wait for the medium to be busy. In the meantime, data may also be transmitted in each of STA1, STA2, and STA5, and each STA waits for DIFS when the medium is monitored idle, and then counts down the backoff slot according to a random backoff count value selected by the STA. Can be performed. In the example of FIG. 6, STA2 selects the smallest backoff count value and STA1 selects the largest backoff count value.
- the remaining backoff time of the STA5 is shorter than the remaining backoff time of the STA1 at the time when the STA2 finishes the backoff count and starts the frame transmission.
- STA1 and STA5 stop counting for a while and wait for STA2 to occupy the medium.
- the STA1 and the STA5 resume the stopped backoff count after waiting for DIFS. That is, the frame transmission can be started after counting down the remaining backoff slots by the remaining backoff time. Since the remaining backoff time of the STA5 is shorter than that of the STA1, the STA5 starts frame transmission. Meanwhile, while STA2 occupies the medium, data to be transmitted may also occur in STA4.
- the STA4 waits for DIFS, performs a countdown according to a random backoff count value selected by the STA4, and starts frame transmission.
- the remaining backoff time of STA5 coincides with an arbitrary backoff count value of STA4.
- a collision may occur between STA4 and STA5. If a collision occurs, neither STA4 nor STA5 receive an ACK, and thus data transmission fails. In this case, STA4 and STA5 may double the CW value, select a random backoff count value, and perform a countdown.
- the STA1 waits while the medium is occupied due to transmission of the STA4 and STA5, waits for DIFS when the medium is idle, and starts frame transmission after the remaining backoff time passes.
- the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing in which the AP and / or STA directly sense the medium.
- Virtual carrier sensing is intended to compensate for problems that may occur in media access, such as a hidden node problem.
- the MAC of the WLAN system may use a network allocation vector (NAV).
- the NAV is a value in which an AP and / or STA currently using or authorized to use a medium instructs another AP and / or STA how long to remain until the medium becomes available.
- the value set to NAV corresponds to a period during which the medium is scheduled to be used by the AP and / or STA transmitting the corresponding frame, and the STA receiving the NAV value is prohibited from accessing the medium (or channel access) during the period. prohibit or defer.
- the NAV may be set, for example, according to the value of the "duration" field of the MAC header of the frame.
- 7 is a diagram for explaining hidden nodes and exposed nodes.
- STA A illustrates an example of a hidden node, in which STA A and STA B are in communication and STA C has information to transmit.
- STA A may be transmitting information to STA B, it may be determined that the medium is idle when STA C performs carrier sensing before sending data to STA B. This is because transmission of STA A (ie, media occupation) may not be sensed at the location of STA C.
- STA B since STA B receives the information of STA A and STA C at the same time, a collision occurs.
- STA A may be referred to as a hidden node of STA C.
- FIG. 7B is an example of an exposed node
- STA B is a case in which STA C has information to be transmitted from STA D while transmitting data to STA A.
- FIG. 7B when STA C performs carrier sensing, it may be determined that the medium is occupied by the transmission of STA B. Accordingly, since STA C is sensed as a medium occupancy state even if there is information to be transmitted to STA D, it must wait until the medium becomes idle. However, since STA A is actually outside the transmission range of STA C, transmission from STA C and transmission from STA B may not collide with STA A's point of view, so STA C is unnecessary until STA B stops transmitting. To wait. At this time, STA C may be referred to as an exposed node of STA B.
- FIG. 8 is a diagram for explaining an RTS and a CTS.
- a short signaling packet such as a request to send (RTS) and a clear to send (CTS) may be used.
- RTS request to send
- CTS clear to send
- the RTS / CTS between the two STAs may allow the surrounding STA (s) to overhear, allowing the surrounding STA (s) to consider whether to transmit information between the two STAs. For example, when an STA to transmit data transmits an RTS frame to an STA receiving the data, the STA receiving the data may inform the neighboring STAs that they will receive the data by transmitting the CTS frame.
- 8A illustrates an example of a method for solving a hidden node problem, and assumes that both STA A and STA C try to transmit data to STA B.
- FIG. 8A When STA A sends the RTS to STA B, STA B transmits the CTS to both STA A and STA C around it. As a result, STA C waits until data transmission between STA A and STA B is completed, thereby avoiding collision.
- FIG. 8 (b) is an example of a method of solving an exposed node problem, and STA C overhears RTS / CTS transmission between STA A and STA B so that STA C is a different STA (eg, STA). It may be determined that no collision will occur even if data is transmitted to D). That is, STA B transmits the RTS to all neighboring STAs, and only STA A having the data to actually transmit the CTS. Since STA C receives only RTS and not STA A's CTS, it can be seen that STA A is out of STC C's carrier sensing.
- STA C overhears RTS / CTS transmission between STA A and STA B so that STA C is a different STA (eg, STA). It may be determined that no collision will occur even if data is transmitted to D). That is, STA B transmits the RTS to all neighboring STAs, and only STA A having the data to actually transmit the CTS. Since STA C receives only
- the WLAN system channel sensing must be performed before the STA performs transmission and reception, and always sensing the channel causes continuous power consumption of the STA.
- the power consumption in the receive state is not significantly different from the power consumption in the transmit state, and maintaining the receive state is also a great burden for the power limited STA (ie, operated by a battery). Therefore, if the STA maintains a reception standby state in order to continuously sense the channel, it inefficiently consumes power without any particular advantage in terms of WLAN throughput.
- the WLAN system supports a power management (PM) mode of the STA.
- PM power management
- the power management mode of the STA is divided into an active mode and a power save (PS) mode.
- the STA basically operates in the active mode.
- the STA operating in the active mode maintains an awake state.
- the awake state is a state in which normal operation such as frame transmission and reception or channel scanning is possible.
- the STA operating in the PS mode operates by switching between a sleep state (or a doze state) and an awake state.
- the STA operating in the sleep state operates at the minimum power, and does not perform frame scanning as well as channel scanning.
- the STA operates in the sleep state for as long as possible, power consumption is reduced, so the STA has an increased operation period. However, it is impossible to operate unconditionally long because frame transmission and reception are impossible in the sleep state. If there is a frame to be transmitted to the AP, the STA operating in the sleep state may transmit the frame by switching to the awake state. On the other hand, when the AP has a frame to transmit to the STA, the STA in the sleep state may not receive it and may not know that there is a frame to receive. Accordingly, the STA may need to switch to the awake state according to a specific period in order to know whether or not the frame to be transmitted to (or, if there is, receive it) exists.
- FIG. 9 is a diagram for describing a power management operation.
- the AP 210 transmits a beacon frame to STAs in a BSS at regular intervals (S211, S212, S213, S214, S215, and S216).
- the beacon frame includes a traffic indication map (TIM) information element.
- the TIM information element includes information indicating that the AP 210 is present with buffered traffic for STAs associated with it and will transmit a frame.
- the TIM element includes a TIM used to inform unicast frames and a delivery traffic indication map (DTIM) used to inform multicast or broadcast frames.
- DTIM delivery traffic indication map
- the AP 210 may transmit the DTIM once every three beacon frames.
- STA1 220 and STA2 222 are STAs operating in a PS mode.
- the STA1 220 and the STA2 222 may be configured to receive a TIM element transmitted by the AP 210 by switching from a sleep state to an awake state at every wakeup interval of a predetermined period. .
- Each STA may calculate a time to switch to the awake state based on its local clock. In the example of FIG. 9, it is assumed that the clock of the STA coincides with the clock of the AP.
- the predetermined wakeup interval may be set such that the STA1 220 may switch to the awake state for each beacon interval to receive the TIM element. Accordingly, the STA1 220 may be switched to an awake state when the AP 210 first transmits a beacon frame (S211) (S221). STA1 220 may receive a beacon frame and obtain a TIM element. When the obtained TIM element indicates that there is a frame to be transmitted to the STA1 220, the STA1 220 sends a PS-Poll (Power Save-Poll) frame requesting the AP 210 to transmit the frame, and the AP 210. It may be transmitted to (S221a). The AP 210 may transmit the frame to the STA1 220 in response to the PS-Poll frame (S231). After completing the frame reception, the STA1 220 switches to the sleep state again.
- S211 beacon frame
- S221a Power Save-Poll
- the AP 210 When the AP 210 transmits the beacon frame for the second time, the AP 210 does not transmit the beacon frame at the correct beacon interval because the medium is busy, such as another device accessing the medium. It can be transmitted at a delayed time (S212). In this case, the STA1 220 switches the operation mode to the awake state according to the beacon interval, but fails to receive the delayed beacon frame, and switches back to the sleep state (S222).
- the beacon frame may include a TIM element set to DTIM.
- the AP 210 delays transmission of the beacon frame (S213).
- the STA1 220 may operate by switching to an awake state according to the beacon interval, and may obtain a DTIM through a beacon frame transmitted by the AP 210. It is assumed that the DTIM acquired by the STA1 220 indicates that there is no frame to be transmitted to the STA1 220 and that a frame for another STA exists. In this case, the STA1 220 may determine that there is no frame to receive, and then switch to the sleep state again.
- the AP 210 transmits the frame to the STA after transmitting the beacon frame (S232).
- the AP 210 transmits a beacon frame fourthly (S214).
- the STA1 220 cannot adjust the wakeup interval for receiving the TIM element because the STA1 220 cannot obtain information indicating that there is buffered traffic for itself through the previous two times of receiving the TIM element.
- the wakeup interval value of the STA1 220 may be adjusted.
- the STA1 220 may be configured to switch the operating state by waking up once every three beacon intervals from switching the operating state for TIM element reception every beacon interval. Accordingly, the STA1 220 cannot acquire the corresponding TIM element because the AP 210 maintains a sleep state at the time when the AP 210 transmits the fourth beacon frame (S214) and transmits the fifth beacon frame (S215).
- the STA1 220 may operate by switching to an awake state and may acquire a TIM element included in the beacon frame (S224). Since the TIM element is a DTIM indicating that a broadcast frame exists, the STA1 220 may receive a broadcast frame transmitted by the AP 210 without transmitting the PS-Poll frame to the AP 210. (S234). Meanwhile, the wakeup interval set in the STA2 230 may be set in a longer period than the STA1 220. Accordingly, the STA2 230 may switch to the awake state at the time S215 at which the AP 210 transmits the beacon frame for the fifth time (S215) and receive the TIM element (S241).
- the STA2 230 may know that there is a frame to be transmitted to itself through the TIM element, and transmit a PS-Poll frame to the AP 210 to request frame transmission (S241a).
- the AP 210 may transmit the frame to the STA2 230 in response to the PS-Poll frame (S233).
- the TIM element includes a TIM indicating whether a frame to be transmitted to the STA exists or a DTIM indicating whether a broadcast / multicast frame exists.
- DTIM may be implemented through field setting of a TIM element.
- 10 to 12 are diagrams for explaining the operation of the STA receiving the TIM in detail.
- the STA may switch from a sleep state to an awake state to receive a beacon frame including a TIM from an AP, interpret the received TIM element, and know that there is buffered traffic to be transmitted to the AP. .
- the STA may transmit a PS-Poll frame to request an AP to transmit a data frame.
- the AP may transmit the frame to the STA.
- the STA may receive a data frame and transmit an acknowledgment (ACK) frame thereto to the AP.
- the STA may then go back to sleep.
- ACK acknowledgment
- the AP may operate according to an immediate response method after transmitting a data frame after a predetermined time (for example, short inter-frame space (SIFS)) after receiving a PS-Poll frame from the STA. Can be. Meanwhile, when the AP fails to prepare a data frame to be transmitted to the STA during the SIFS time after receiving the PS-Poll frame, the AP may operate according to a deferred response method, which will be described with reference to FIG. 11.
- a predetermined time for example, short inter-frame space (SIFS)
- SIFS short inter-frame space
- the STA transitions from the sleep state to the awake state to receive the TIM from the AP and transmits the PS-Poll frame to the AP through contention as in the example of FIG. 10. If the AP does not prepare a data frame during SIFS even after receiving the PS-Poll frame, the AP may transmit an ACK frame to the STA instead of transmitting the data frame. When the data frame is prepared after transmitting the ACK frame, the AP may transmit the data frame to the STA after performing contention. The STA may transmit an ACK frame indicating that the data frame was successfully received to the AP and go to sleep.
- STAs may transition from a sleep state to an awake state to receive a beacon frame containing a DTIM element from the AP. STAs may know that a multicast / broadcast frame will be transmitted through the received DTIM.
- the AP may transmit data (ie, multicast / broadcast frame) immediately after the beacon frame including the DTIM without transmitting and receiving the PS-Poll frame.
- the STAs may receive data while continuously awake after receiving the beacon frame including the DTIM, and may switch back to the sleep state after the data reception is completed.
- the Physical Layer Convergence Protocol (PLCP) Packet Data Unit (PPDU) frame format may include a Short Training Field (STF), a Long Training Field (LTF), a SIG (SIGNAL) field, and a Data field.
- STF Short Training Field
- LTF Long Training Field
- SIGNAL SIG
- Data field e.g., Data field
- L-STF legacy-STF
- L-LTF legacy-LTF
- SIG field et Data Unit
- PPDU frame format e.g., HT-mixed format PPDU, HT-greenfield format PPDU, VHT (Very High Throughput) PPDU, etc.
- an additional (or other type) may be used between the SIG field and the data field.
- the STF, LTF, and SIG fields may be included.
- the STF is a signal for signal detection, automatic gain control (AGC), diversity selection, precise time synchronization, etc.
- the LTF is a signal for channel estimation, frequency error estimation, and the like.
- the STF and LTF may be referred to as a PCLP preamble, and the PLCP preamble may be referred to as a signal for synchronization and channel estimation of an OFDM physical layer.
- the SIG field may include a RATE field and a LENGTH field.
- the RATE field may include information about modulation and coding rate of data.
- the LENGTH field may include information about the length of data.
- the SIG field may include a parity bit, a SIG TAIL bit, and the like.
- the data field may include a SERVICE field, a PLC Service Data Unit (PSDU), a PPDU TAIL bit, and may also include a padding bit if necessary.
- Some bits of the SERVICE field may be used for synchronization of the descrambler at the receiving end.
- the PSDU corresponds to a MAC PDU defined in the MAC layer and may include data generated / used in an upper layer.
- the PPDU TAIL bit can be used to return the encoder to zero.
- the padding bit may be used to adjust the length of the data field in a predetermined unit.
- MAC PDUs are defined according to various MAC frame formats, and basic MAC frames are composed of a MAC header, a frame body, and a frame check sequence (FCS).
- FCS frame check sequence
- the MAC frame consists of a MAC PDU and can be transmitted / received through the PSDU of the data portion of the PPDU frame format.
- the null-data packet (NDP) frame format means a frame format of a type that does not include a data packet. That is, the NDP frame refers to a frame format including only PLCP header parts (ie, STF, LTF, and SIG fields) in the general PPDU format and not including the remaining parts (ie, data fields).
- the NDP frame may be referred to as a short frame format.
- An STA that is allowed to active polling may perform polling to the AP immediately after wakeup. That is, an STA that is allowed to active polling may perform a polling operation (eg, transmission of a PS-Poll frame) without having to listen to a beacon after waking up.
- a polling operation eg, transmission of a PS-Poll frame
- Such a STA may be referred to as a non-TIM STA in that polling may be performed without checking a TIM element included in the beacon frame.
- an STA performing polling when there is data to be transmitted to itself according to a TIM element included in a beacon frame may be referred to as a TIM STA.
- Active polling can be classified into a scheduled active polling type and an unscheduled active polling type.
- the AP schedules a wakeup time of the STA, and the STA wakes up at the scheduled time to perform an operation for uplink / downlink (UL / DL) transmission, and the STA is a beacon There is no need to track it.
- the AP may allow the STA or STA group to transmit an uplink frame at any point in time when the STA or STA group wakes up, and the STA does not need to track the beacons.
- the active polling STA that does not track the beacon may miss the information, time stamp information, etc. updated through the beacon. Therefore, the active polling STA may request that the AP provide such information immediately upon waking up. The AP may immediately provide the information to the STA, or may inform the STA to receive the information through the next beacon. To this end, the AP may provide the STA with a timer for receiving the next beacon.
- RAW refers to a time interval in which only channel access of a specific STA or STA group is allowed.
- the AP may inform the STA (s) of the RAW allocation information through the beacons.
- FIG. 13 is a diagram for explaining RAW allocation.
- More than one RAW may be set within one beacon interval.
- RAW may be divided into one or more time slots.
- the reference at the time point at which the slots are divided is called a slot boundary.
- the length of one slot is referred to as slot duration.
- the STA that wakes up in the target beacon transmission time (TBTT) listens to the beacon frame and can know the information about the slot duration in each RAW through the beacon frame.
- TBTT target beacon transmission time
- the duration of the plurality of slots may be set to be the same.
- slot durations in different RAWs may be set differently.
- the STA may determine a slot in which its channel access is allowed as allocated by the AP.
- the STA may operate in a sleep state before its channel access slot.
- the STA may initiate channel access on an EDCA basis at the slot boundary of its channel access slot.
- the AP may inform whether Transmission Opportunity (TXOP) or transmission in the TXOP can continue cross the slot boundary. If the transmission of the STA is not allowed to cross the slot boundary, the STA may perform channel access without waiting for the ProbeDelay time when the STA wakes up at the slot boundary.
- TXOP Transmission Opportunity
- the AP may inform the paged STA of the channel access slot, and the STA may perform competition in the slot. Informing the channel access slot may be based on the TIM of the beacon.
- the paged STA may start contention at the slot boundary.
- the STA may transmit a PS-Poll or trigger frame to the AP based on EDCA after the slot boundary of its channel access slot.
- the AP may inform the paged STA that it will transmit traffic after the downlink BU delivery slot.
- the downlink BU transfer slot for each STA may be indicated by a management frame.
- the AP may protect the PS-Poll or trigger frame by setting the NAV.
- the paged STA may ignore the NAV set by the AP. If NAV is set, only paged STAs can transmit PS-Poll or trigger frames in RAW.
- the AP may allow the STA or STA group to transmit the uplink frame at any time.
- the AP may allocate a channel access slot that allows competition of the STA or the STQ group through the beacon frame.
- the STA may wake up in the TBTT to listen to the beacon frame and determine its channel access slot based on the information in the beacon frame.
- the STA may start channel access based on EDCA after the slot boundary of its channel access slot.
- the AP may allocate a channel access slot to the STA. In this case, the STA may start channel access based on EDCA after the slot boundary of its channel access slot.
- the RAW duration may be expressed as T RAW
- the slot duration may be expressed as T S.
- the slot mapping function is defined as in Equation 1 below.
- Equation 1 i is an index of a slot allocated to the STA.
- Equation 1 is the AID of the STA.
- N offset is an offset value given to provide fairness between STAs indicated in the TIM.
- a time stamp value or an FCS may be used as an offset value.
- Equation 1 mod denotes a modulo operation.
- RAW allocation as described above may be defined by a RPS (RAW Parameter Set) information element included in a beacon frame or a short beacon frame.
- the RPS information element (IE) may include subfields as shown in Table 1 below.
- a RAW may exist in which RAW does not allow channel access of the TIM STAs, and the AP may inform the TIM STAs of such RAW information. Since the non-TIM STA does not need to listen to the beacon and can be active polled, it can perform channel access for the polling operation at the time of wake-up. By informing the TIM STAs of RAWs that are prohibited from accessing the TIM STAs, In response, the RAW may be used as a time interval for non-TIM STAs to access the channel.
- periodic RAW may be set.
- the AP may allocate resources for scheduled active polling STAs and inform corresponding resource allocation information. Information about the PRAW is not indicated through a short beacon frame, but may be indicated through a general beacon frame. If PRAW is configured, the AP may periodically allocate resources to a group of scheduled active polling STAs. The resources allocated for the PRAW may not change until the updated PRAW information is broadcast. Resources for the scheduled active polling STA may be allocated within a PRAW duration. If the scheduled active polling STA has a data packet to transmit, it may wake up in a designated slot in the PRAW to perform a basic CCA and then transmit the packet. TIM STAs are not allowed channel access during PRAW. Each STA in the PRAW may perform channel access according to an EDCA-based channel access scheme.
- a channel access slot of an STA may be allocated through the RPS IE, and the STA may attempt channel access in the allocated slot. If the field indicating whether to allow cross boundary transmission in the slot definition in the RPS IE is set to 1, the STA goes beyond the boundary of the slot allocated to the STA (ie, in a slot for another STA). Channel access cannot be performed.
- the STA may continue channel access beyond the boundary of the slot allocated to the STA (ie, in a slot for another STA). However, since there is no slot after the RAW end point or the boundary of the RAW, even if transmission beyond the slot boundary is allowed (i.e. cross-boundary transmission to the slot is allowed), it is possible It is not defined whether or not the STA assigned the slot can continue channel access beyond the RAW endpoint. On the other hand, if the cross boundary transmission for the slot is not allowed, since the STA does not continue the transmission beyond the slot allocated to the slot, it does not matter whether the transmission can continue beyond the RAW endpoint.
- the STAs assigned slots in the RAW stop transmitting at the RAW end point (or RAW boundary) and retransmit at another point when their channel access is allowed. You can try If the system defines that the RAW end point (or RAW boundary) can be exceeded, an STA assigned a slot in the RAW may continue to perform channel access beyond the RAW end point (or RAW boundary).
- the channel usage efficiency may be degraded because the channel cannot be used even if the channel is idle after the RAW boundary.
- the system is defined as capable of crossing the RAW boundary, if there is a target wake time (TWT) for another RAW or non-TIM STA after some RAW terminates, the probability of collision of channel access due to congestion This can be high.
- TWT target wake time
- PRAW the area of the PRAW (e.g., the RPS IE for the PRAW is provided only in the initial beacon and not currently in the beacon or short beacons). May cause congestion in the PRAW.
- the present invention proposes a method of adaptively setting whether transmission is allowed beyond the RAW end point (or RAW boundary). Accordingly, the efficiency of resource utilization can be increased by RAW or more dynamically in consideration of the system situation.
- the AP when the AP allocates a RAW to the STA through the beacon, the AP may include information indicating whether to allow channel access beyond the end point of the corresponding RAW in the beacon.
- a field indicating whether to allow RAW cross boundary transmission eg, RAW Cross Boundary Transmission Allowance
- Table 2 shows an example of the RPS IE further including this new field.
- the AP transmits by setting the value of the RAW cross boundary transmission allowance (CBTA) field in the RPS IE to the first value (or 1), and does not allow the transmission beyond the RAW boundary.
- the AP may transmit by setting the value of the RAW CBTA field to a second value (or 0). For example, when the RAW CBTA value is set to 0, when RAW2 exists after RAW1 and many STAs are allocated to RAW2, when RAW1 PRAW exists, when there is an urgent downlink frame to be transmitted after RAW1, And the case where the TWT of the Non-TIM STA (s) is set after RAW1.
- FIG. 14 is a view for explaining an example of the RAW allocation method according to the present invention.
- the value of the slot CBTA ie, information indicating whether transmission is allowed beyond the slot boundary
- the RAW CBTA ie, RAW boundary
- the value of information indicating whether transmission is allowed is set to 1.
- RAW CBTA may be set to 1 in consideration that no other RAW exists after RAW1, it is not limited to this reason. Since the value of the RAW CBTA is set to 1, an STA allocated a slot in RAW1 may transmit an uplink frame beyond a RAW boundary.
- first, second, third and fourth slots in RAW1 are allocated to STA1, STA2, STA3 and STA4, respectively.
- STA1 and STA2 may not attempt channel access in the first and second slots because they do not have an uplink frame to transmit.
- the STA3 assigned to the third slot wakes up and transmits an uplink frame based on the EDCA, and the frame may continue beyond the slot boundary and may continue beyond the RAW boundary.
- the STA4 has an uplink frame to be woken up and transmitted at the boundary of the slot allocated thereto, the STA4 cannot transmit the uplink frame because the STA3 occupies the channel.
- FIG. 15 is a diagram for explaining another example of the RAW allocation method according to the present invention.
- a value of slot CBTA is set to 1 and a value of RAW CBTA is set to 0 in an RPS IE for RAW1 provided through a beacon.
- RAW CBTA may be set to 0 considering that RAW2 does not exist after RAW1, it is not limited to this reason. Since the value of the RAW CBTA is set to 0, an STA allocated a slot in RAW1 cannot transmit an uplink frame over a RAW boundary. For example, STA1 and STA2 may not attempt channel access in the first and second slots because they do not have an uplink frame to transmit.
- the STA3 assigned to the third slot wakes up and transmits an uplink frame based on the EDCA, and the frame may continue beyond the slot boundary, but may not continue beyond the RAW boundary. Therefore, uplink frame transmission of STA3 must be completed or stopped before the RAW endpoint. Meanwhile, although the STA4 has an uplink frame to be woken up and transmitted at the boundary of the slot allocated thereto, the STA4 cannot transmit the uplink frame because the STA3 occupies the channel.
- FIG. 16 is a view for explaining another example of the RAW allocation method according to the present invention.
- RAW CBTA is basically included in the RPS IE sent through the beacon, but you can change the value of the RAW CBTA during the beacon interval.
- the RAW CBTA value may be set through a predetermined frame transmitted from the AP during the beacon interval.
- the predetermined frame that carries the RAW CBTA information during the beacon interval may be an NDP frame (eg, NDP-CTS frame, NDP-ACK frame, etc.) or a general control frame (eg, CTS frame or ACK frame). Etc.) may be used.
- a value of slot CBTA is set to 1 and a value of RAW CBTA is set to 0 in an RPS IE for RAW1 provided through a beacon. Since the value of the RAW CBTA is set to 0, an STA allocated a slot in RAW1 cannot transmit an uplink frame over a RAW boundary.
- the AP includes the RAW CBTA field in the NDP frame (for example, the NDP-CTS frame in FIG. 16) and transmits it.
- the value of the RAW CBTA field may be set to one.
- the STA (s) receiving the NDP frame and allocating slots in the RAW1 may transmit an uplink frame across the RAW boundary.
- the first, second, third and fourth slots in RAW1 are allocated to STA1, STA2, STA3 and STA4, respectively.
- STA1 assigned to the first slot wakes up and transmits an uplink frame on an EDCA basis, and the frame may continue beyond the slot boundary.
- STA2 and STA3 have uplink frames to wake up and transmit in the second slot and the third slot, respectively, but cannot transmit an uplink frame because STA1 occupies a channel.
- STAs in the wake-up state in the fourth slot may receive an NDP-CTS frame in which the RAW CBTA is set to 1 (that is, changing a RAW CBTA value previously set to 0 to 1).
- the STA4 since the STA4 wakes up and has an uplink frame to be transmitted in the fourth slot, the STA2, STA3, and STA4 may attempt channel access in the fourth slot. STA3 can transmit the uplink frame through the competition. Since the value of the RAW CBTA is set to 1, the STA3 can continue to transmit the uplink frame over the RAW boundary. That is, as shown in FIG. 16, uplink frame transmission of STA3 started in the fourth slot of RAW1 may continue in RAW2.
- FIG. 17 is a view for explaining another example of the RAW allocation method according to the present invention.
- a slot CBTA value is set to 1 and a RAW CBTA value is set to 1 in an RPS IE for RAW1 provided through a beacon. Since the value of the RAW CBTA is set to 1, an STA allocated a slot in RAW1 may transmit an uplink frame beyond a RAW boundary. Further, assume that the first, second, third and fourth slots in RAW1 are allocated to STA1, STA2, STA3 and STA4, respectively. For example, STA1 assigned to the first slot wakes up and transmits an uplink frame on an EDCA basis, and the frame may continue beyond the slot boundary.
- STA2 has an uplink frame to wake up and transmit in the second slot, but cannot transmit an uplink frame because STA1 occupies a channel.
- the STA2 may know that the channel usage of the STA1 is finished by receiving an ACK frame transmitted from the AP to the STA1, or when receiving a frame such as the NDP-CTS, may recognize the channel as idle and attempt to use the channel.
- STAs in the wake-up state in the third slot may receive an NDP-CTS frame in which the RAW CBTA is set to 0 (that is, changing the RAW CBTA value previously set to 1 to 0).
- the STA3 since the STA3 wakes up and has an uplink frame to be transmitted in the third slot, the STA2 and the STA3 may attempt channel access in the third slot. Through competition, STA3 can transmit an uplink frame. Since the value of the RAW CBTA is set to 0, an STA allocated a slot in RAW1 cannot transmit an uplink frame over a RAW boundary. That is, as shown in FIG. 17, uplink frame transmission of STA3 started in the third slot of RAW1 may continue beyond the slot boundary, but may not continue beyond the RAW boundary.
- uplink frame transmission of STA3 must be completed or stopped before the end point of RAW1. Meanwhile, although the STA4 has an uplink frame to be woken up and transmitted at the boundary of the slot allocated thereto, the STA4 cannot transmit the uplink frame because the STA3 occupies the channel.
- STA4 since STA4 does not receive an NDP-CTS frame in which the value of the RAW CBTA is set to 0 (that is, STA4 operates in a sleep state until the fourth slot), STA4 is configured through the RPS IE of the beacon. Therefore, the value of RAW CBTA is recognized as 1. Accordingly, STA4 may attempt uplink frame transmission beyond the RAW boundary. That is, while other STAs recognize the value of the RAW CBTA as 0, a problem may occur in that only STA4 recognizes the value of the RAW CBTA as 1.
- a predetermined frame including a RAW CBTA value may be transmitted before the RAW boundary.
- the predetermined frame that carries the RAW CBTA information before the RAW boundary may be an NDP frame (eg, NDP-CTS frame, NDP-ACK frame, etc.) or a general control frame (eg, CTS frame or ACK frame). Etc.) may be used.
- FIG. 18 is a view for explaining another example of the RAW allocation method according to the present invention.
- an NDP-CTS frame (that is, an NDP frame that sets the value of the RAW CBTA to 0) transmitted in the third slot of RAW1 may be received by the STA2 and the STA3 in the wake-up state. It cannot be received in the STA4 in the sleep state. That is, STA2 and STA3 recognize the value of the RAW CBTA as 0 as set through the NDP-CTS frame, and STA4 recognizes the value of the RAW CBTA as 1 as set through the beacon frame. Accordingly, the uplink frame transmission of the STA3 started in the third slot of the RAW1 can continue beyond the slot boundary, but the uplink frame transmission of the STA3 must be completed or stopped before the end point of the RAW1.
- STA4 has an uplink frame that wakes up and transmits at the boundary of a slot allocated thereto, but STA4 cannot transmit an uplink frame because STA3 occupies a channel, and when the channel occupancy of STA3 ends, STA4 accesses a channel. You can try
- the AP may transmit the NDP-CTS frame including the RAW CBTA set to 0 before the RAW boundary of the RAW1, and the STA4 in the wake-up state may receive the NDP-CTS frame. Accordingly, it may be recognized that the RAW CBTA value is set to 0 and may not attempt to access the channel beyond the RAW boundary.
- STA2 and STA3 may also receive an NDP-CTS frame including RAW CBTA information transmitted before the RAW boundary.
- STA2 and STA3 may determine whether to allow transmission beyond the RAW boundary according to the last received RAW CBTA information.
- RAW CBTA value set for the STA2 and the STA3 is 0 and the RAW CBTA value additionally received before the RAW boundary is also 0, it may be finally recognized as the value of the RAW CBTA.
- FIG. 19 is a view for explaining another example of the RAW allocation method according to the present invention.
- a response frame (eg, an ACK frame or an NDP-ACK) for uplink frame transmission from STA3 is used.
- a RAW CBTA value may be included in the response frame for transmission.
- NDP frame eg, an NDP-CTS frame or an NDP-ACK frame, etc.
- Information for allowing or scheduling channel access of a specific STA in a specific slot may be provided through an NDP frame.
- Such an operation may be referred to as a polling operation of slot-by-slot scheduling for a specific STA. Accordingly, the efficiency of resource utilization can be further increased by dynamically scheduling which STAs are allowed to access a channel in a specific slot.
- RAW CBTA information is provided through an NDP frame (for example, an NDP-CTS frame or an NDP-ACK frame), the present invention is not limited thereto.
- RAW CBTA information may be provided from the AP to the STA during the beacon interval or before the RAW boundary (via a CTS frame or ACK frame).
- FIG. 20 illustrates a method of accessing a channel based on a restricted access window according to an embodiment of the present invention.
- the AP may allocate RAW to the STA.
- RAW allocation information may be provided through the RPS IE of the beacon frame.
- the AP may provide RAW CBTA information to the STA.
- the STA may determine whether to perform the transmission beyond the RAW boundary based on the RAW CBTA information, and perform the transmission operation accordingly.
- the RAW allocation information of step S2010 and the RAW CBTA information of step S2020 may be provided to the STA through the RPS IE included in the beacon frame.
- additional RAW CBTA information may be provided to the STA during the RAW.
- FIG. 20 Although the example method described in FIG. 20 is represented by a series of operations for simplicity of description, it is not intended to limit the order in which the steps are performed, and each step may be performed simultaneously or in a different order as necessary. have. In addition, not all the steps illustrated in FIG. 20 are necessary to implement the method proposed by the present invention.
- 21 is a block diagram illustrating a configuration of a wireless device according to an embodiment of the present invention.
- the AP 10 may include a processor 11, a memory 12, and a transceiver 13.
- the STA 20 may include a processor 21, a memory 22, and a transceiver 23.
- the transceivers 13 and 23 may transmit / receive wireless signals and, for example, may implement a physical layer in accordance with the IEEE 802 system.
- the processors 11 and 21 may be connected to the transceivers 13 and 21 to implement a physical layer and / or a MAC layer according to the IEEE 802 system. Processors 11 and 21 may be configured to perform operations according to the various embodiments of the present invention described above.
- modules for implementing the operations of the AP and the STA according to various embodiments of the present invention described above may be stored in the memory 12 and 22 and executed by the processors 11 and 21.
- the memories 12 and 22 may be included in the processors 11 and 21 or may be installed outside the processors 11 and 21 and connected to the processors 11 and 21 by known means.
- the processor 11 of the AP 10 may be configured to transmit RAW CBTA information to the STA 20 using the transceiver 13 when RAW is allocated to the STA 20.
- the processor 21 of the STA 20 may be configured to receive RAW CBTA information from the AP 10 using the transceiver 23 when RAW is allocated by the AP 10. Accordingly, the processor 21 of the STA 20 may be configured to perform transmission from the STA 10 based on the RAW CBTA information. For example, when the RAW CBTA information is set to the first value, transmission of the STA beyond the boundary of the RAW is allowed, and accordingly, the processor 21 notifies the transmission from the STA 20 after the RAW boundary. It may be operable to attempt using the transceiver 23. Alternatively, when the RAW CBTA information is set to the second value, transmission of the STA that crosses the boundary of the RAW is not allowed, and accordingly, the processor 21 does not perform transmission from the STA 20 after the RAW boundary. Can be operated.
- Embodiments of the present invention described above may be implemented through various means.
- embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.
- a method according to embodiments of the present invention may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), and Programmable Logic Devices (PLDs). It may be implemented by field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.
- ASICs Application Specific Integrated Circuits
- DSPs Digital Signal Processors
- DSPDs Digital Signal Processing Devices
- PLDs Programmable Logic Devices
- FPGAs field programmable gate arrays
- processors controllers, microcontrollers, microprocessors, and the like.
- the method according to the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function that performs the functions or operations described above.
- the software code may be stored in a memory unit and driven by a processor.
- the memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.
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Abstract
Description
Claims (14)
- 무선 통신 시스템에서 스테이션(STA)이 채널 액세스를 수행하는 방법에 있어서,상기 STA에 대해서 제한된 액세스 윈도우(RAW)가 할당되는 경우, 액세스 포인트(AP)로부터 RAW 크로스 경계 전송 허용(CBTA) 정보를 수신하는 단계; 및상기 RAW CBTA 정보에 기초하여 상기 STA으로부터의 전송을 수행하는 단계를 포함하고,상기 RAW CBTA 정보가 제 1 값으로 설정되는 경우, 상기 RAW의 경계를 넘어서는 상기 STA의 전송이 허용되는, 채널 액세스 수행 방법.
- 제 1 항에 있어서,상기 RAW CBTA 정보가 제 2 값으로 설정되는 경우, 상기 RAW의 경계를 넘어서는 상기 STA의 전송이 허용되지 않는, 채널 액세스 수행 방법.
- 제 1 항에 있어서,상기 RAW는 하나 이상의 슬롯으로 분할되고,상기 하나 이상의 슬롯의 경계를 넘어서는 상기 STA의 전송이 허용되는 경우에, 상기 RAW CBTA 정보에 기초하여 상기 STA으로부터의 전송이 수행되는, 채널 액세스 수행 방법.
- 제 1 항에 있어서,상기 RAW CBTA 정보는 RAW 파라미터 세트 정보요소(RPS IE)에 포함되는, 채널 액세스 수행 방법.
- 제 4 항에 있어서,상기 RPS IE는 비콘 프레임을 통하여 상기 AP로부터 수신되는, 채널 액세스 수행 방법.
- 제 1 항에 있어서,하나 이상의 RAW CBTA 정보가 상기 RAW 도중에 상기 AP로부터 수신되는, 채널 액세스 수행 방법.
- 제 6 항에 있어서,상기 하나 이상의 RAW CBTA 정보는 널-데이터 패킷(NDP) 프레임 또는 제어 프레임을 통하여 상기 AP로부터 수신되는, 채널 액세스 수행 방법.
- 제 7 항에 있어서,상기 NDP 프레임은, NDP-CTS(Clear To Send) 프레임 또는 NDP-ACK(Acknowledgment) 프레임인, 채널 액세스 수행 방법.
- 제 7 항에 있어서,상기 제어 프레임은 CTS 프레임 또는 ACK 프레임인, 채널 액세스 수행 방법.
- 제 6 항에 있어서,상기 하나 이상의 RAW CBTA 정보 중에서 마지막으로 수신된 RAW CBTA 정보에 기초하여 상기 STA으로부터의 전송이 수행되는, 채널 액세스 수행 방법.
- 제 1 항에 있어서,상기 RAW는 하나 이상의 슬롯으로 분할되고,상기 하나 이상의 RAW CBTA 정보는 상기 하나 이상의 슬롯의 시작 후 또는 상기 RAW의 경계 전에 전송되는, 채널 액세스 수행 방법.
- 무선 통신 시스템에서 액세스 포인트(AP)가 스테이션(STA)의 채널 액세스를 지원하는 방법에 있어서,상기 STA에 대해서 제한된 액세스 윈도우(RAW)가 할당되는 경우, 상기 STA에게 RAW 크로스 경계 전송 허용(CBTA) 정보를 전송하는 단계를 포함하고,상기 RAW CBTA 정보에 기초하여 상기 STA으로부터의 전송이 수행되며,상기 RAW CBTA 정보가 제 1 값으로 설정되는 경우, 상기 RAW의 경계를 넘어서는 상기 STA의 전송이 허용되는, 채널 액세스 지원 방법.
- 무선 통신 시스템에서 채널 액세스를 수행하는 스테이션(STA) 장치에 있어서,송수신기; 및프로세서를 포함하고,상기 프로세서는, 상기 STA에 대해서 제한된 액세스 윈도우(RAW)가 할당되는 경우, 액세스 포인트(AP)로부터 RAW 크로스 경계 전송 허용(CBTA) 정보를 상기 송수신기를 이용하여 수신하고; 상기 RAW CBTA 정보에 기초하여 상기 STA으로부터의 전송을 상기 송수신기를 이용하여 수행하도록 설정되며,상기 RAW CBTA 정보가 제 1 값으로 설정되는 경우, 상기 RAW의 경계를 넘어서는 상기 STA의 전송이 허용되는, 채널 액세스 수행 STA 장치.
- 무선 통신 시스템에서 스테이션(STA)의 채널 액세스를 지원하는 액세스 포인트(AP) 장치에 있어서,송수신기; 및프로세서를 포함하고,상기 프로세서는, 상기 STA에 대해서 제한된 액세스 윈도우(RAW)가 할당되는 경우, 상기 STA에게 RAW 크로스 경계 전송 허용(CBTA) 정보를 상기 송수신기를 이용하여 전송하는 단계를 포함하고,상기 RAW CBTA 정보에 기초하여 상기 STA으로부터의 전송이 수행되며,상기 RAW CBTA 정보가 제 1 값으로 설정되는 경우, 상기 RAW의 경계를 넘어서는 상기 STA의 전송이 허용되는, 채널 액세스 지원 AP 장치.
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US14/651,192 US9913292B2 (en) | 2012-12-11 | 2013-12-11 | Method and device for restricted access window-based channel access in WLAN system |
KR1020157018400A KR20150104568A (ko) | 2012-12-11 | 2013-12-11 | 무선랜 시스템에서 제한된 액세스 윈도우 기반 채널 액세스 방법 및 장치 |
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US20150334742A1 (en) | 2015-11-19 |
KR20150104568A (ko) | 2015-09-15 |
US9913292B2 (en) | 2018-03-06 |
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