WO2015105248A1 - 무선랜 시스템에서 짧은 mac 헤더를 지원하는 프레임 송수신 방법 및 장치 - Google Patents
무선랜 시스템에서 짧은 mac 헤더를 지원하는 프레임 송수신 방법 및 장치 Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
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- H—ELECTRICITY
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- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1829—Arrangements specially adapted for the receiver end
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- H—ELECTRICITY
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- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
- H04L5/0055—Physical resource allocation for ACK/NACK
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L63/00—Network architectures or network communication protocols for network security
- H04L63/04—Network architectures or network communication protocols for network security for providing a confidential data exchange among entities communicating through data packet networks
- H04L63/0428—Network architectures or network communication protocols for network security for providing a confidential data exchange among entities communicating through data packet networks wherein the data content is protected, e.g. by encrypting or encapsulating the payload
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- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/06—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols the encryption apparatus using shift registers or memories for block-wise or stream coding, e.g. DES systems or RC4; Hash functions; Pseudorandom sequence generators
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/70—Services for machine-to-machine communication [M2M] or machine type communication [MTC]
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- H04W84/10—Small scale networks; Flat hierarchical networks
- H04W84/12—WLAN [Wireless Local Area Networks]
Definitions
- the following description relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting / receiving a frame supporting a short MAC header in a WLAN system.
- Wireless LAN is based on radio frequency technology, using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), or the like. It is a technology that allows wireless access to the Internet in a specific service area.
- PDA personal digital assistant
- PMP portable multimedia player
- IEEE 802.11 ⁇ supports High Throughput (HT) with data throughput rates up to 540 Mbps and higher, and also uses multiple antennas at both the transmitter and receiver to minimize transmission errors and optimize data rates.
- HT High Throughput
- MIMC MIMC Multiple Inputs and Multiple Outputs
- Machine-to-Machine (M2M) communication technology is being discussed as the next generation communication technology.
- 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.
- An object of the present invention is to provide a sequence number management method when a short MAC header is used to save STA power and prevent malfunction. It is also an object of the present invention to provide a scheme for configuring an encrypted data unit when a short MAC header is used. [6]
- the technical problems to be achieved in the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above are apparent to those skilled in the art from the following description. Can be understood.
- a method for receiving a frame by a station (STA) in a wireless communication system includes a sequence control (Sequence Control; SO field) Determining a packet number (PN) by using a value of the SC field and a partial packet number (PN) value stored in the STA; and using the PN for the frame. And performing a decryption, if the sequence number value of the SC field of the received frame is smaller than the previous sequence number value, the partial PN value stored in the STA is increased by one.
- the arithmetic operation may be performed when the decoding is performed after block ACK reordering for the frame.
- a station (STA) device for receiving a frame in a wireless communication system according to another embodiment of the present invention, a transceiver; And a processor.
- the processor is configured to control the transceiver to receive the frame including a Sequence Control (SC) field; Determine a packet number (PN) using a value of the SC field and a partial packet number (PN) value stored in the STA;
- the PN may be configured to perform decryption on the frame. If the sequence number value of the SC field of the received frame is smaller than the previous sequence number value, the operation of increasing the partial PN value stored in the STA by 1 may include reordering the block ACK for the frame. It may be performed when the decoding is performed after ing).
- the block ACK reordering may include sorting in sequence of increasing sequence number values of a plurality of frames including the frame. [12] can be determined by concatenating ion of PNO, PN1, PN2, PN3, PN4, and PN5, each 8 bits in size.
- the value of the SC field may be configured to a value obtained by linking the PN0 and the PN1.
- the partial PN value may be configured by linking the PN2, PN3, PN4, and PN5.
- the sequence number value of the SC field of the received MPDU is smaller than the previous sequence number value, the sequence number may be rolled over.
- the frame may be a media access control (MAC) protocol data unit (MPDU).
- MAC media access control
- MPDU protocol data unit
- a method and apparatus for managing sequence number when a short MAC header is used can be provided. Further, according to the present invention, a method and apparatus for configuring an encrypted data unit when a short MAC header is used can be provided.
- FIG. 1 is a diagram showing 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 shows 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.
- 5 is a view for explaining a link setup process in a WLAN system. 6 illustrates a backoff process.
- FIG. 7 is a diagram for explaining a hidden node and an exposed node.
- 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 a group based AID.
- FIG. 14 is a diagram for explaining an example of a frame structure used in an IEEE 802.11 system.
- FIG. 15 is a diagram for explaining an example of a long range PLCP frame format.
- FIG. 16 is a transmission flow illustrating a repetition technique for configuring a PLCP frame format for a 1 MHz bandwidth.
- FIG 17 illustrates an example of an extended capability element according to the present invention.
- 18 is a block diagram illustrating CCMP encapsulation.
- FIG. 19 is a diagram illustrating an exemplary configuration of a frame control field of a short MAC header according to the present invention.
- FIG. 20 is a diagram showing an exemplary configuration of an AAD according to the present invention.
- Figure 21 is a diagram showing an exemplary configuration of a Nonce according to the present invention.
- Figure 22 illustrates an exemplary configuration of an encrypted MPDU according to the present invention.
- FIG. 23 is a diagram illustrating an MSDU reception flow in a MAC data plane structure.
- 24 is a diagram for explaining a method according to an example of the present invention.
- 25 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 configurations or features of one embodiment may be included in another embodiment, or may be replaced with other configurations or features of another embodiment.
- Embodiments of the present invention may be supported by standard documents disclosed in at least one of the IEEE 802 system, the 3GPP system, the 3GPP LTE and LTE-Advanced (LTE-A) system, and the 3GPP2 system, which are radio access systems. 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.
- CDM Code Division Multitude Access FDMA
- Frequency Diversity Access FDMA
- Time Diversity Access TDMA
- Orthogonal Frequency Diversity Access FDMA
- SC-FDMA Single Carrier Frequency Division Multiple Access
- CDMA may be implemented by radio technologies such as UTRA Jniversal Terrestrial Radio Access (CDMA2000) or CDMA2000.
- TDMA may be implemented in a wireless technology such as Global System for Mobile Communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolut ion (EDGE).
- GSM Global System for Mobile Communications
- GPRS General Packet Radio Service
- EDGE Enhanced Data Rates for GSM Evolut ion
- DMA is IEEE Wireless technology such as 802.11 (Wi-Fi), IEEE 802. 16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA) and the like.
- Wi-Fi Wi-Fi
- WiMAX IEEE 802. 16
- FIG. 1 is a diagram illustrating an exemplary structure of an IEEE 802.11 system to which the present invention can be applied.
- the IEEE 802.11 structure may be composed of a plurality of components, and a WLAN supporting transparent STA mobility for higher layers may be provided by their interaction.
- a basic service set (BSS) may correspond to a basic building block in an IEEE 802.11 LAN.
- FIG. 1 exemplarily shows that two BSSs (BSS1 and BSS2) exist and include two STAs 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 BSA (Basi c Service Area).
- BSA Base c 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.
- BSSCBSS1 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 is not 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, or entering or exiting the BSS region.
- 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 at i on may be set up dynamically and may include the use of a distributed system service (DSS).
- DSS distributed system service
- FIG. 2 illustrates another exemplary structure of an IEEE 802.11 system to which the present invention can be applied.
- the structure of Figure 1 The distribution system (Distr ibut ion System (DS)), the distribution system medium (Distr ibut ion System Medium (DSM)), access point (Access Point (AP)), etc. are added.
- DS Distributr ibut ion System
- DSM Distribution System Medium
- AP Access Point
- the direct station-to-station distance in a LAN can be limited by physical layer (PHY) performance. In some cases, this distance limit may be striking, but in some cases, communication between more distant stations may be necessary.
- a distribution system (DS) can be configured to support extended coverage.
- [57] 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).
- the IEEE 802.11 standard logically separates 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 mobile devices by providing seamless integration of multiple BSSs and providing logical services for handling addresses to destinations.
- the AP refers to an entity that enables access to the DS through 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 a functionality of STA, and provide a function of allowing 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 network and the address used by the AP for communication on the DSM need not necessarily be the same.
- FIG. 3 is a diagram showing 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 having any size and complexity may be configured with 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 LUXLogical Link Control (LUX) 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.
- LUX LUXLogical Link Control
- IEEE 802.11 does not assume anything about the relative physical location of the BSSs in FIG. 3, and all of the following forms are possible.
- BSSs can be partially overlapped, which is a form commonly used to provide continuous coverage. Further, BSS they may not be physically connected to, and, logically, there is no limit to the distance between the BSS.
- the BSSs may be located at the same physical location, which may 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. This may be the case when an ad-hoc network is operating at a location where an ESS network is present, or when IEEE 802. 11 networks are configured that are physically overlapped by different organisations, or at least two different accesses at the same location and This may correspond to the ESS network type when a security policy is required.
- 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 work like laptops and mobile phones. In general, this is a device that the user directly handles.
- STAl, 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 (MS). Mobile Terminal), Mobile Subscriber Station (MSS), or the like.
- the AP includes a base station (BS), a node-B (Node-B), an evolved Node-B (eNB), and a base transceiver system (BTS) in other wireless communication fields. It is a concept that stands for Femto BS.
- An operation of an STA operating in a WLAN system may be described in terms of a layer structure.
- the hierarchy may be implemented by a processor.
- the STA may have a plurality of tradeoff structures.
- the hierarchical structure covered by the 802.11 standard document is mainly a MAC sublayer and a physical (PHY) layer on the DLUData Link Layer.
- the PHY may include a Physical Layer Convergence Procedure (PLCP) entity, a PMDCPhysical Medium Dependent (PMDCP) entity, and the like.
- PLCP Physical Layer Convergence Procedure
- PMDCP PMDCPhysical Medium Dependent
- the MAC sublayer and the PHY conceptually contain management entities called MAC sublayer management entities (MLMEs) and physical layer management entities (PLMEs), respectively.These entities provide a layer management service interface on which layer management functions operate. .
- SME Station Management Entity
- LMEs Layer Management Entities
- a primitive refers to a set of elements or parameters related to a particular purpose.
- XX-GET The request primitive of the given MIB attribute (management information base attribute information) Used to request a value.
- the conf irm primitive is used to return the appropriate MIB attribute information value if Status is "success", otherwise return an error indication in the Status field.
- XX-SET The request primitive is used to request that the indicated MIB attribute be set to the given value. If the MIB attribute means a specific operation, this is to request that the operation be performed.
- XX-SET The conf irm primitive confirms that the indicated MIB attribute is set to the requested value when status is "successful”, otherwise it is used to return an error condition in the status field. If this means, this confirms that the operation has been performed.
- the MLME and the SME may exchange various MLME_GET / SET primitives through a MLME_SAP (Service Access Point).
- various PLME_GET / SET primitives can be exchanged between PLME and SME through PLME_SAP and between MLME and PLME through MLME-PLME_SAP.
- FIG. 5 is a diagram for explaining a general link setup process.
- the STA In order for a STA to set up a link and transmit data to and from a network, the STA first discovers the network, performs an authenticated icat ion, establishes an association ion, and establishes an establ i sh. For example, authentication procedures for security must be performed.
- the link setup process may also be referred to as a session initiation process and a 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. The network identification process existing in a specific area is called scanning.
- FIG. 5 illustrates an example of a network discovery operation including an active scanning process.
- active scanning the STA performing scanning moves channels A probe request frame is sent to discover what AP is around and wait for a response.
- the responder transmits a probe response frame to the STA that has transmitted the probe request frame in response to the probe request frame.
- the answering machine may be an STA that transmits a beacon frame last 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 (for example, number 2).
- Channel to perform scanning (ie, probe request / answer response 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 so that an STA performing scanning can find a 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 an advantage of smaller 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 (f i rst authent i cat ion) process 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 authentic i cat ion request frame to the AP, and in response thereto, the AP transmits an authentic i cat ion response frame to the STA.
- An authentication frame used for authentication request / response corresponds to a management frame.
- An authentication frame includes an authentication algorithm number, an authentication transaction sequence number, a status code, a chal lenge text, a Robust Security Network, and a finite loop. It may include information about a group (Finite Cyclic 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 transmit 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, a beacon listening interval, a service set identifier (SSID), supported rates, supported channels, and RSN.
- SSID service set identifier
- an association voice response frame may include information related to various capabilities, a status code, an association ID (AID), a support rate, an enhanced distributed channel access (EDCA) parameter set, an RCP KReceived channel power indicator (RSNI), and a received signal to RSNI.
- Information such as a noise indicator, a mobility domain, a timeout interval (association comeback time), an overlapping BSS scan parameter, and a TIM broadcast voice answer QoS map.
- This may correspond to some examples of information that may be included in the association request / response frame, and may be replaced with other information or further include additional information.
- a security setup process may be performed in 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 / answer.
- the authentication process may be referred to as a first authentication process, and the security setup process of step S540 may be simply referred to as an authentication process.
- RSNA Robust Security Network Association
- the security setup process of step S540 may include, for example, a private key setup through 4-way handshaking through an EAPOUExtensible Authentication Protocol over LAN frame. have.
- the security setup process may be performed according to a security scheme not defined in the IEEE 802.11 standard.
- IEEE 802.11 ⁇ is a relatively recent technical standard. IEEE 802.11 ⁇ aims to increase the speed and reliability of networks and to extend the operating distance of wireless networks. More specifically, IEEE 802.11 ⁇ supports High Throughput (HT) with data throughput rates 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. It is based on MIMOC Multiple Inputs and Multiple Outputs technology.
- HT High Throughput
- the next generation WLAN system supporting Very High Throughput is the next version of the IEEE 802.11 ⁇ WLAN system (e.g., IEEE 802. llac), which is used by the MAC Service Access Point (SAP). It is one of the recently proposed IEEE 802.11 WLAN system to support the data processing speed of lGbps or more.
- the next generation WLAN system supports transmission of a multi-user multiple input multiple output (MU-MIM0) scheme in which a plurality of STAs simultaneously access a channel in order to efficiently use a wireless channel.
- MU-MIM0 multi-user multiple input multiple output
- the AP may simultaneously transmit packets to one or more STAs paired with MIM0.
- TV whitespace TV whitespace
- the idle frequency band e.g., 54-698 MHz band
- IEEE 802.11af the idle frequency band
- the whitespace is only a licensed band that can be used preferentially by an authorized user.
- An authorized user refers to a user who is permitted to use an authorized band, and may also be referred to as an authorized device, a primary user, an incumbent user, or the like.
- an AP and / or STA operating in a WS should provide a protection ion function for an authorized user.
- a protection ion function for an authorized user.
- an authorized user such as a microphone
- the AP and / or STA cannot use the frequency band corresponding to the corresponding WS channel.
- 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 the 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 a spectrum sensing mechanism, an energy detect ion method and a signal detect ion method 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 (Machine-to-Machine) communication technology has been discussed as a next-generation communication technology.
- IEEE 802.11 WLAN system a technical standard for supporting M2M communication is being developed as IEEE 802.11ah.
- M2M communication refers to a communication method that includes one or more machines (Machine), may also be referred to as MTC (Machine Type Communicat ion) or thing communication.
- a machine is an entity (ent i ty) that does not require human intervention or intervention.
- devices such as meters or vending machines equipped with wireless communication modules, as well as user devices such as smartphones that can automatically connect and communicate with the network without user intervention / intervention, 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 a server (appl icat ion server), and the like.
- D2D device-to-device
- server communication between vending machines and servers, point of sale devices and servers, and electricity, gas or water meters and servers.
- M2M communication-based applications may include security (security), transport (ions), health care (health care) and the like.
- M2M communication should be able to support the transmission and reception of a small amount of data at low speeds in an environment where there are many devices.
- M2M communication should be able to support the number of STAs.
- WLAN system it is assumed that a maximum of 2007 STAs are associated with one AP, but in M2M communication, methods for supporting a case where a larger number (approximately 6000 STAs) are associated with one AP are discussed. It is becoming.
- many applications that support / require low data rates are expected in M2M communication.
- an STA may print the presence or absence of data to be transmitted to itself based on a TIMCTraf Indicat ion Map element. Is being discussed.
- M2M communication is expected to have a lot of traffic with a very long transmission / reception interval.
- WLAN technology is rapidly evolving, and in addition to the above examples, direct link setup, improvement of media streaming performance, support for high speed and / or large initial session setup, support for extended bandwidth and operating frequency, etc. Technology is being developed for.
- the basic access mechanism of MAC is a carrier sense multiple access avoidance (CSMA / CA) mechanism.
- the CSMA / CA mechanism also known as the Distributed Coordinat Ion Funct Ion (DCF) of the IEEE 802.11 MAC, employs a "l isten before talk" access mechanism by default.
- DCF Distributed Coordinat Ion Funct Ion
- the AP and / or STA may be able to A Clear Channel Assessment (CCA) that senses a radio channel or medium during a time interval (eg, DCF Inter-Frame Space (DIFS)) may be performed.
- CCA Clear Channel Assessment
- DIFS DCF Inter-Frame Space
- the medium is idle (frame is transmitted through the medium, if the medium is detected as occupied status, the AP and / or STA does not start its own transmission and accesses the medium.
- the frame transmission may be attempted after waiting by setting a delay period (for example, a random backoff period), for example, by applying a random backoff period, several STAs wait for different times. It is expected to attempt frame transmission later, thus minimizing col ision.
- a delay period for example, a random backoff period
- HCF Hypoid ion Funct ion.
- HCF is based on the DCF and PCF (Point Coordinat ion Funct ion).
- the PCF refers to a polling-based synchronous access method that polls 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 Control led Channel Access (HCCA).
- EDCA is a competition based approach for providers to provide data frames to multiple users, and HCCA uses a non-competitive based channel access method using polling mechanisms.
- HCF includes a media access mechanism to improve the quality of service (QoS) of the WLAN, and the QoS data in both contention period (CP) and contention free period (CFP). Can be transmitted.
- QoS quality of service
- CP contention period
- CCP contention free period
- FIG. 6 illustrates a backoff process
- the STAs may attempt to transmit data (or frames).
- the STAs may select a random backoff count and wait for the corresponding slot time, and then attempt transmission.
- the random backoff count has a packet number value and may be determined as one of values ranging from 0 to CW.
- CW is the 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 slot 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 occupied. In the meantime, data may be transmitted in each of STAl, 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 STA5 is shorter than the remaining backoff time of STA1.
- 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.
- data to be transmitted may also occur in STA4.
- the STA4 waits as much as DIFS, and then 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, and in this case, a stratification may occur between STA4 and STA5.
- both STA4 and STA5 do not receive an ACK and thus fail to transmit data.
- the STA4 and STA5 may double the CW value and then select a random backoff count value and perform a countdown.
- STA1 is a fun song of STA4 and STA5. If the media is idle while the media is idle,
- 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 for instructing other APs and / or STAs of an AP and / or STA that are currently using or are authorized to use a medium 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 frame, and the STA receiving the NAV value is prohibited from accessing the medium during the period.
- the NAV may be set, for example, according to the value of the "durat ion" field of the MAC header of the frame.
- FIG. 7 is a diagram for explaining a hidden node and an exposed node.
- FIG. 7A 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 stratification 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 where STA C has information to be transmitted from STA D in a situation in which data is transmitted 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, STA C transmits to STA D. Even if there is information, it is sensed as being occupied by the media and must wait until the media is 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 RTSC request to send and clear to send (CTS) may be used.
- the RTS / CTS between the two STAs may enable the neighboring STA (s) to overhear, allowing the neighboring STA (s) to consider whether to transmit information between the two STAs.
- the STA receiving the data may inform the neighboring STAs that it will receive the data by transmitting the CTS frame.
- FIG. 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 the data transmission of STA A and STA B is completed, thereby avoiding the dolmen.
- FIG. 8 (b) illustrates an example of a method for solving an exposed node problem, and STA C overhears RTS / CTS transmission between STA A and STA B so that STA C may identify another STA (eg, For example, even when data is transmitted to STA D, it may be determined that no stratification occurs. That is, STA B transmits the RTS to all the 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.
- 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 does not differ significantly compared to the power consumption in the transmit state, and maintaining the receive state is a great burden for the power limited STA (ie, operated by a battery). Therefore, the STA continuously If the standby state is maintained for sensing, power consumption is inefficiently consumed 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 while 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 As the STA operates in the sleep state for as long as possible, power consumption decreases, so that the STA increases the 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 be transmitted to the STA, the STA in the sleep state may not receive it and may not know that there is a frame to receive. Therefore, the STA may need to switch to the awake state according to a specific period in order to know whether there is a frame to be transmitted to it (and also to receive it if there is).
- FIG. 9 is a diagram for explaining a power management operation.
- an 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 TIM Traffic Indicat ion Map information element.
- the TIM information element includes information indicating that A 210 is present with buffered traffic for STAs associated with it and will transmit a frame.
- the TIM element includes a TIM used to indicate a unicast frame, and a DTIM (del ivery ways indi cat ion map) used to indicate a multicast (mult icast) or brocastcast frame.
- the AP 210 may transmit the DTIM once every three beacon frames.
- STAK220 and STA2 222 are STAs operating in a PS mode.
- STA1 220 and STA2 222 are in a sleep state every wakeup interval of a predetermined period. It may be configured to receive the TIM element transmitted by the AP 210 by switching to the awake state.
- 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 STAK220 may switch to the awake state for each beacon interval to receive the TIM element. Accordingly, the STA 220 may be switched to the awake state when the A 210 first transmits the beacon frame (S211) (S221). STAK220 may receive a beacon frame and obtain a TIM element. When the acquired TIM element indicates that there is a frame to be transmitted to the STA 220, the STAK220 transmits a PS-Pol 1 (Power Save-Pol l) frame to the A 210 requesting the AP 210 to transmit the frame. It may be (S221a). The AP 210 may transmit the frame to the STAK220 in response to the PS-Pol l frame (S231). After receiving the frame, the STA 220 switches to the sleep state again.
- PS-Pol 1 Power Save-Pol l
- the AP 210 transmitting the beacon frame for the second time, since the medium is occupied by another device accessing the medium such that the AP 210 is busy, the AP 210 matches the beacon frame according to the correct beacon interval. It can be transmitted at a delayed time without transmitting the data (S212). In this case, the STAK220 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 AK210 delays transmission of the beacon frame (S213).
- the STAK220 operates by switching to an awake state according to the beacon interval, and may acquire a DTIM through a beacon frame transmitted by the AP 210. It is assumed that the DTIM acquired by the STAK220 indicates that there is no frame to be transmitted to the STAK220 and that a frame for another STA exists. In this case, the STAK220 may determine that there is no frame to receive, and switch to the sleep state to operate.
- the AP 210 transmits the frame to the STA after the beacon frame transmission (S232).
- a 210 transmits a beacon frame for the fourth time (S214).
- STAK220 may not obtain information indicating that there is buffered traffic for itself through reception of the previous two TIM elements, and thus may adjust wakeup interval for receiving TIM elements. have.
- the wakeup interval value of the STAK220 may be adjusted.
- the STAU220 may be configured to switch the operating state by waking up once every three beacon intervals from the operating state for receiving the TIM element every beacon interval. Accordingly, the STAK220 cannot acquire the corresponding TIM element because the AP 210 maintains a sleep state (S215) at the time when the AP 210 transmits the fourth beacon frame (S214) and the fifth beacon frame (S215).
- the STAU220 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 STAK220 may receive a broadcast frame transmitted by the AP 210 without transmitting the PS-Pol l frame to the AP 210 ( S234). Meanwhile, the wakeup interval set in the STA2 230 may be set at a longer period than the STAK220. Accordingly, the STA2 230 may switch to the awake state and receive the TIM element at the time S215 when the AP 210 transmits the beacon frame for the fifth time (S241).
- the STA2 230 may know that there is a frame to be transmitted to itself through the TIM element, and transmit a PS-Pol l frame to the AP 210 to request frame transmission (S241a).
- the AP 210 may transmit a frame to the STA2 230 in response to the PS-Pol l frame (S233).
- the TIM element includes a TIM indicating whether there is a frame to be transmitted to the STA 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 describing in detail the operation of the STA receiving the TIM.
- the STA transitions from a sleep state to an awake state to receive a beacon frame including a TIM from an AP, interprets the received TIM element, and indicates that there is buffered traffic to be transmitted to the AP. Able to know.
- the STA may transmit a PS-Pol l frame to request transmission of a data frame from the AP after contending with other STAs for medium access for PS-Pol l frame transmission.
- PS transmitted by STA—An AP that receives a Pol l frame may transmit a frame to the STA. have.
- the STA may receive a data frame and transmit an acknowledgment (ACK) frame to the AP.
- the STA may then go back to sleep.
- ACK acknowledgment
- the AP immediately transmits a data frame after a predetermined time (for example, a short inter-frame space (SIFS)) after receiving a PS-Pol l frame from the STA. Can be operated according to. Meanwhile, when the AP fails to prepare a data frame to be transmitted to the STA during the SIFS time after receiving the PS-Pol l frame, the AP may operate according to a delayed response method, which will be described with reference to FIG. 11. .
- a predetermined time for example, a short inter-frame space (SIFS)
- SIFS short inter-frame space
- an operation of receiving a TIM from the AP by switching from the sleep state to the awake state and transmitting a PS-Pol l frame to the AP through contention is the same as the example of FIG. 10.
- the AP fails to prepare a data frame during SIFS even after receiving the PS-Pol l frame, the AP may transmit an ACK frame to the STA instead of transmitting the data 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 has been successfully received to the AP and go to sleep.
- the AP transmits a DTIM.
- 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 transmitting a beacon frame including a DTIM without transmitting and receiving a PS-Pol l 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.
- STAs may have a data frame to be transmitted for themselves through STA identification information included in a ⁇ element. You can check whether it exists.
- the STA identification information may be information related to an association ion identifier (AID), which is an identifier assigned to the STA at the time of association with the ⁇ .
- AID is used as a unique identifier for each STA in one BSS. For example, in the current WLAN system, the AID may be assigned to one of values from 1 to 2007. In the currently defined WLAN system, 14 bits may be allocated for an AID in a frame transmitted by an AP and / or STA, and an AID value may be allocated up to 16383, but in 2008, 16383 is set as a reserved value. It is.
- the TIM element according to the existing definition is not suitable for application of an M2M application in which a large number of STAs (eg, more than 2007) may be associated with one AP.
- the TIM bitmap size is so large that it cannot be supported by the existing frame format, and is not suitable for M2M communication considering low transmission rate applications.
- M2M communication it is expected that the number of STAs in which a received data frame exists during one beacon period is very small. Therefore, considering the application example of the M2M communication as described above, since the size of the TIM bitmap is expected to be large, but most of the bits have a value of 0, it is expected that a technique for efficiently compressing the bitmap.
- bitmap compression technique there is a scheme for omitting consecutive zeros in front of a bitmap and defining it as an offset (of fset) value.
- the compression efficiency is not high. For example, when only frames to be transmitted to only two STAs having AIDs of 10 and 2000 are buffered, the compressed bitmap has a length of 1990 but all have a value of 0 except at both ends.
- the inefficiency of bitmap compression is not a big problem, but when the number of STAs increases, such inefficiency may be a factor that hinders overall system performance. .
- the AID may be divided into groups to perform more efficient data transmission.
- Each group is assigned a designated group ID (GID).
- GID group ID
- AIDs allocated on a group basis will be described with reference to FIG. 13.
- FIG. 13 (a) is a diagram illustrating an example of an AID allocated on a group basis.
- the first few bits of the AID bitmap may be used to indicate a GID.
- the first two bits of the AID bitmap can be used to represent four GIDs. have. If the total length of the AID bitmap is N bits, the first two bits (B1 and B2) indicate the GID of the corresponding AID.
- FIG. 13B is a diagram illustrating another example of an AID allocated on a group basis.
- the GID may be allocated according to the location of the AID.
- AIDs using the same GID may be represented by an offset and a length value.
- GID 1 is represented by an offset A and a length B, it means that AIDs A through A + B-1 have GID 1 on the bitmap.
- FIG. 13B it is assumed that AIDs of all 1 to N4 are divided into four groups. In this case, AIDs belonging to GID 1 are 1 to N1, and AIDs belonging to this group may be represented by offset 1 and length N1.
- AIDs belonging to GID 2 may be represented by offset N1 + 1 and length N2-N1 + 1
- AIDs belonging to GID 3 may be represented by offset N2 + 1 and length N3-N2 +
- GID AIDs belonging to 4 may be represented by an offset N3 + 1 and a length N4-N3 + 1.
- the TIM element shortage problem for a large number of STAs is solved and efficient data transmission and reception are performed.
- channel access may be allowed only to STA (s) corresponding to a specific group during a specific time interval, and channel access may be restricted to other STA (s).
- a predetermined time interval in which only specific STA (s) are allowed access may be referred to as a restricted access window (RAW).
- RAW restricted access window
- FIG. 13C illustrates a channel access mechanism according to the beacon interval when the AID is divided into three groups.
- the first beacon interval (or the first RAW) is a period in which channel access of an STA corresponding to an AID belonging to GID 1 is permitted, and channel access of STAs belonging to another GID is not allowed.
- the first beacon includes a TIM element only for AIDs corresponding to GID 1.
- the second beacon frame includes a TIM element only for AIDs having GID 2, and thus only channel access of the STA corresponding to the AID belonging to GID 2 is allowed during the second beacon interval (or second RAW).
- the third beacon frame contains a TIM element for AIDs with GID 3 only, so that during the third beacon interval (or third RAW) only the channel access of the STA corresponding to the AID belonging to GID 3 Is allowed.
- the fourth beacon frame again includes a TIM element for only AIDs having GID 1, and accordingly, only the channel access of the STA corresponding to the AID belonging to GID 1 is allowed during the fourth beacon interval (or fourth RAW). Then, even in each of the fifth and subsequent beacon intervals (or fifth and subsequent RAWs), only channel access of the STA belonging to the specific group indicated in the TIM included in the beacon frame may be allowed.
- the order of GIDs allowed according to the beacon interval shows a cyclic or periodic example, but is not limited thereto. That is, by including only the AID (s) belonging to a particular GID (s) in the TIM element, allowing channel access only to the STA (s) corresponding to the particular AID (s) during a particular time interval (e.g., a particular RAW). And operate in a manner that does not allow channel access of the remaining STA (s).
- the group-based AID allocation scheme as described above may also be referred to as a hierarchical structure of the TIM. That is, the entire AID space may be divided into a plurality of blocks, and only channel access of STA (s) (that is, STA of a specific group) corresponding to a specific block having a non-zero value may be allowed. Accordingly, the TIM is divided into small blocks / groups so that the STAs can easily maintain the TIM information, and the blocks / groups can be easily managed according to the class, quality of service (QoS), or purpose of the STA.
- QoS quality of service
- a two-level hierarchy is shown, but a hierarchical TIM may be configured in the form of two or more levels.
- the entire AID space may be divided into a plurality of page groups, each page group may be divided into a plurality of blocks, and each block may be divided into a plurality of sub-blocks.
- the first N1 bits represent a page ID (i.e., PID)
- the next N2 bits represent a block ID
- the next N3 bits Represents a sub-block ID and may be configured in such a way that the remaining bits indicate the STA bit position in the sub-block.
- [1501 frame structure 14 is a diagram for explaining an example of a frame structure used in an IEEE 802.11 system.
- 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 (Data) field. Can be.
- the most basic (eg, non-HT (High Throughput)) PPDU frame format may consist of only L-STF (Legacy-STF), L-LTF (Legacy-LTF), SIG field, and data field.
- PPDU frame format for example, HT-mixed format PPDU, HT-green format PPDU, VHT (Very High Throughput) PPDU, etc.
- an additional (or other type) may be added between the SIG field and the data field.
- STF, LTF, and SIG fields may be included.
- STF is a signal for signal detection, AGC (Automatic Gain Control), diversity selection, precise time synchronization, etc.
- LTF is a signal for channel estimation and frequency error estimation.
- 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 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 (Protocol Data Unit) 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.
- the MAC PDU is defined according to various MAC frame formats, and a basic MAC frame includes a MAC header, a frame body, and a frame check sequence (FCS).
- the MAC frame may be composed of MAC PDUs and may be transmitted / received through the PSDU of the data portion of the PPDU frame format.
- the MAC header includes a frame control field, a duration (DuraUon) / ID field, an address field, and the like.
- Frame control fields are used to send / receive frames. It may include necessary control information.
- the duration / ID field may be set to a time for transmitting a corresponding frame.
- the frame control field of the MAC header may include Protocol Version, Type, Subtype, To DS, From DS, More Fragment, Retry, Power Management, More Data, Protected Frame, and Order subfields.
- the contents of each subfield of the frame control field may refer to the IEEE 802.11-2012 standard document.
- Table 1 below describes the To DS subfield and the From DS subfield in the frame control field defined in the existing IEEE llac standard.
- the four address fields (Address 1, Address 2, Address 3, and Address 4) of the MAC header are BSSIDCBasi c Servi ce Set Ident if ier (SA), Source Address (SA), Dest inat ion Address (DA), and TA ( It may be used to indicate a Transmitter Address (RA), a Receiver Address (RA), etc., and may include only some of the four address fields according to the frame type.
- the purpose of the address field may be specified by the relative position of the address field (Address 1-Address 4) in the MAC header, regardless of the type of address of the field. For example, the recipient address can always be determined based on the contents of the Address 1 field of the received frame.
- the recipient address of the CTS frame can always be obtained from the Address 2 field of the corresponding RTS frame.
- the recipient address of the ACK frame can always be obtained from the Address 2 field of the frame that is the target of the acknowledgment.
- Table 2 below describes the contents of the address fields (Address 1-Address 4) of the MAC header according to the values of the To DS subfield and the From DS subfield in the frame control field of the MAC header.
- RA means a recipient address
- TA means a sender address
- DA means a destination address
- SA means a source address.
- MSDU means MAC SDU (Service Data Unit), which is a unit of information transferred between MAC SAP (Servi ce Access Point).
- Aggregate-MSDU refers to a frame format for delivering a plurality of MAC SDUs through one MAC PDU. The values of these address fields (Address 1, Address 2, Address 3, or Address 4) may be set in the form of a 48-bit Ethernet MAC address.
- the null-data packet (NDP) frame format refers to a frame format of a type that does not include a data packet. That is, the NDP frame contains only the PIXP header portion (ie, STF, LTF, and SIG fields) in the general PPDU format, and the rest (ie, data). Field) means a frame format not included.
- the NDP frame may be referred to as a short frame format.
- the Sequence Control field of the MAC header can be used.
- the sequence control field includes a sequence number and a fragment number. MPDUs corresponding to parts of the same MSDU have the same sequence number, and different MSDUs have different sequence numbers.
- the STA allocates a sequence number of a frame according to a counter that is incremented by 1 for each new MSDU (eg, a modulo-4096 counter starting from 0).
- the STA transmitting the frame stores (or caches) the last used sequence number for each receiver address (RA).
- the STA receiving the frame caches a set of a sender address (TA), a sequence number, and a fragment number of the most recently received frame.
- the TA may be determined from the value of the Address 2 field of the received frame. If the Retry field of the frame control field is set to 1 and a frame having the same sequence number (or the same fragment number) is received from the same TA, the receiving STA determines that the frame is a duplicate frame. You can reject it.
- the present invention proposes a compression scheme of a MAC header to perform communication at low power.
- the MAC header compression scheme proposed in the present invention uses, for example, lMHz / 2MHz / 4MHz / 8MHz / 16MHz channel bandwidth and operates in a frequency band below 1 GHz (sub 1 GHz; S1G). It can be applied to a WLAN system.
- the MAC header is essentially included in a frame for data transmission. If the size of the MAC header is reduced (i.e., the overhead of the MAC header is reduced), the operation of generating, transmitting, and receiving the MAC frame of the STA may be simplified, and thus the power consumption of the STA may be reduced. have.
- a wireless LAN system for example, a system according to the IEEE 802.11ah standard
- S1G Sub 1 GHz
- S1G Sub 1 GHz
- the operation of a sensor or a meter type STA that is characterized by low transmission rate and low power is mainly defined.
- a power saving mechanism is absolutely important for such sensor type STAs.
- the STA needs to minimize unnecessary waking conditions and needs to effectively transmit data to be transmitted and received at waking times.
- a WLAN system operating in the S1G band it is required to configure a frame with low power consumption while supporting long-range transmission.
- it may be considered to repeat the fields of the frame more than twice on the time axis or the frequency axis.
- the size of the MAC header is increased according to field repetitive coding, a problem may occur in that power consumption for frame processing of the STA is increased.
- the present invention proposes a MAC header compression scheme to solve this problem. To this end, a method of configuring a frame in a WLAN system operating in the S1G band will be described first.
- the communication in the S1G band has much wider coverage than the indoor indoor WLAN system due to the propagation characteristics, and down-clocking the PHY defined in the existing IEEE 802.11ac system to 1/10. clocking).
- 2/4/8/16/8 + 8 z channel bandwidth in the S1G band by down-clocking the 20/40/80/160/80 + 80 MHz channel bandwidth supported by the 802.1 lac system to 1/10. It can be provided as.
- the guard interval (GI) is increased 10-fold to 8 // s in the 802.1 lac system.
- the PHY preamble Since there is no legacy device already operating in the S1G band, it is important to design the PHY preamble as effectively as possible in the S1G band without having to consider backward compatibility.
- the easiest way to think about is to design the S1G ⁇ preamble by down-clocking the previously defined HT-GreenField PLCP frame format (see IEEE 802.11 ⁇ standard) to 1/10. For example, it can be used for bandwidths above 2 MHz.
- Long distance by repeating the STF / LTF / SIG / DATA fields of the frame format of the S1G PHY structure used for the bandwidth of 2MHz or more to support long-distance communication more than twice on the time axis or the frequency axis PLCP frames can also be configured.
- 15 is a diagram for explaining an example of a long range PUP frame format.
- the PLCP frame format of FIG. 15 is composed of STF, LTF1, SIG, LTF2-LTFN, and Data fields similar to the Green-ield format defined in IEEE 802.11 ⁇ , but transmission of the preamble portion compared to Green-ield. It can be understood that time is more than doubled by repetition.
- a PLCP frame format such as the example of FIG. 15 may be used for 1 MHz bandwidth and may be referred to as a 1 MHz PPDU format.
- the STF field of the 1 MHz PPDU of FIG. 15 has the same periodicity as the STF (2 symbol length) in the PPDU for a bandwidth of 2 ⁇ z or more, the repetition (rep2) technique is applied in time. 4 symbol lengths (e.g. 160 / S), and 3 dB power boosting is applied.
- the LTF1 field of the 1 MHz PPDU of FIG. 15 is designed to be orthogonal in the frequency domain with the LTF1 field (2 symbol length) in the PPDU for a bandwidth of 2 MHz or more, and repeated four times in time to obtain a 4-symbol length.
- the SIG field of the 1 MHz PPDU of FIG. 15 may be repeatedly coded.
- a SIG field in a PPDU for a bandwidth of 2 MHz or more may be applied to QPSKC Quadrature Phase Shift Keying (MCS), Binary PSK (BPSK), etc. as a Modular Ion and Coding Scheme (MCS), and has a length of 2 symbols.
- MCS Quadrature Phase Shift Keying
- BPSK Binary PSK
- MCS Modular Ion and Coding Scheme
- the SIG field of the 1 MHz PPDU is configured such that the lowest MCS (ie, BPSK) and repetitive coding (rep2) are applied, the rate is 1/2, and may be defined as 6 symbols long.
- the LTFN field from the LTF2 field of the 1 MHz PPDU of FIG. 15 may be included in the case of MIM0, and each LTF field has one symbol length.
- the repetition scheme may or may not be applied to the Data field of the 1 MHz PPDU of FIG. 15.
- 16 is a transmission flow illustrating a repetition technique for configuring a PLCP frame format for a 1 MHz bandwidth.
- the scrambler of FIG. 16 may scramble the data in order to reduce the probability that 0 or 1 is repeated long.
- FEC Forward Error Correction
- the data may be encoded, and may include a binary convolutional encoder or a low density parity check (LDPC) encoder.
- LDPC low density parity check
- 2x block-wise repet it ion means that x encoded information bits of each OFDM symbol (if the encoding rate is 1/2, x / 2 information in each OFDM symbol) Bits may be encoded to generate X encoded information bits), which may be repeated in units of blocks to output 2x information bits.
- NCBPS coded bits per symbol may be included if the lowest MSC (eg MCS0) is applied in one spatial stream (SS).
- the interleaver may perform interleaving (or repositioning) to prevent adjacent noise bits from being continuously contiguous on the decoder side.
- the BPSK mapper can convert (or map to complex symbols) the encoded data bits into BPSK constellation points.
- time-spatial streams can be mapped to transport chains.
- Complex symbols may be transformed into a time domain block through an Inverse Discrete Fourier Transform (IDFT).
- IDFT Inverse Discrete Fourier Transform
- GI & Window an operation of implementing a guard interval (GI) by prepending a portion of the symbol itself to the symbol can be performed, and the edges of each symbol ( 6 (1 3 )) can be performed. Winding may be performed to soften and increase spectral decay Transmission symbols may be generated at the analog and R radio frequencies.
- the duration of one PPDU may be too long, resulting in a decrease in transmission efficiency and an increase in power consumption of the STA.
- the present invention proposes a specific scheme for the MAC header compression scheme that can be used for efficient data transmission in a WLAN system.
- the AP can perform a function as a router.
- the OSKOpen System Interconnect ion 7 layer described computer network protocol design and communication divided into layers is shown in Table 3 below.
- the AP when the AP does not function as a router, the AP performs only functions of a physical layer and a data link layer (MAC layer, LLCCLogi cal Link Control) layer. can do. Therefore, the AP needs four addresses (ie, source address (SA), destination address (DA sender address (TA), and receiver address (RA)) to receive the frame and deliver the frame to the correct destination.
- SA source address
- RA receiver address
- the WLAN system uses four address fields in the header of the MAC frame, as described with reference to Fig. 14. The contents of the four address fields include the To DS subfield and the From DS in the frame control field of the MAC header.
- the Address 4 field is not used because it does not exist in the current WLAN system, so the AP generally serves as a router. If the AP fails to perform the operation, three address fields are required for the AP to receive the frame and deliver the frame to the correct destination.
- the AP acts as a router, a network layer, a transport layer (eg, TCP / IP (Transmi), together with a physical layer and a data link layer (MAC binding, LLC binding) ss i on Control Protocol / Internet Protocol) layer).
- a transport layer eg, TCP / IP (Transmi)
- MAC binding, LLC binding ss i on Control Protocol / Internet Protocol
- Such an AP may transmit only TA and RA except for SA and DA in the MAC layer.
- the role of the delivery of the correct frame by detecting the SA and DA can be performed by the IP layer.
- the frame of the MAC header performs the transmission of the correct frame even if only the two address fields indicating TA and RA (for example, the address of the AP and the address of the STA) are included in the frame. can do.
- the AP may perform a router function. Should be However, not all APs can perform the functions of a router, so the AP must inform other STAs of capability information indicating whether it can function as a router.
- Figure 17 is a diagram for explaining an example of the extended capability element according to the present invention.
- the Element ID field may be set to a value indicating that the corresponding element is an Extended Capabilities element.
- the Length field may be set to a value of the number of octets corresponding to the length of the Capabilities field.
- the Capabilities field is a bit field indicating information on the capability of the STA (or AP STA) for transmitting the element.
- the length of the Capabilities field may be represented by a variable n, and each bit position indicates whether a specific capability is supported.
- the STA may check the value of the 1 bit to determine whether the AP can perform MAC header compression by performing a router function.
- extended capability elements may be included in the association request / answer frame, re-association request / answer frame, beacon frame, probe response frame, and the like.
- MAC header compression when MAC header compression is performed to include only two address fields of TA and RA as address information in the MAC header, it may be referred to as a compressed MAC frame format (or a short MAC frame frame format).
- TA and RA may be defined as shown in Table 4 below.
- TA and RA are determined according to a transmission direction.
- DL downlink
- UL uplink
- TA is set to the address of the STA transmitting the frame
- RA is set to the address of the AP.
- MAC header compression may be performed by excluding address information from the MAC header (that is, including only essential RA and TA and omitting other address information).
- the present invention proposes a method for further reducing the overhead of the address information itself included in the MAC header.
- the address field of the existing MAC header is. It is defined to be set in the form of a 48-bit long MAC address.
- the present invention proposes to use an association identifier (AID) instead of the MAC address of the STA.
- AID is defined to be 16 bits long. Therefore, when using AID, the overhead of the MAC header can be further reduced.
- TA and RA of the compressed MAC header proposed in the present invention may be defined as shown in Table 5 below.
- a TA for example, an Address 2 field
- an RA for example, an Address 1 field
- STA STA of a STA that receives a frame. It is set to AID.
- a TA eg, an Address 2 field
- AID AID of a STA that transmits a frame
- BSSID MAC address of the AP.
- the STA receiving the frame converts (or maps) the AID included in the MAC header of the frame into the MAC address and converts (or maps) the MAC address. ) Store the MAC address in memory (or cache) along with the sequence number. This is to support retransmission for the compressed MAC frame.
- an STA that receives a DL frame from an AP stores a MAC address corresponding to a BSSID included in a TA address field (ie, an Address 2 field) of the DL frame together with a sequence number in a cache. For an access category in the DL frame If the information is included, the BSSID, Sequence Number, and Access Category are stored in the cache.
- the AP that receives the IL frame from the STA may check the STA AID included in the TA address field (ie, the Address 2 field) of the UL frame. Since the STA AID is assigned by the AP, the AP knows the MAC address (that is, the mapping relationship between the STA AID and the STA MAC address) of the STA to which the corresponding AID is assigned. Accordingly, the AP may know the STA MAC address from the STA AID included in the address field (ie, the Address 2 field) of the UL frame. The AP then stores the STA MAC ' address identified by the AID (ie, mapped to the AID) in the cache along with the Sequence Number. If the UL frame includes information on the Access Category, the STA MAC Address, Sequence Number and Access Category are stored in the cache.
- retransmission for a compressed MAC frame may be properly performed.
- the MAC header compression scheme and the sequence control scheme proposed by the present invention are necessary. .
- the normal MAC header is used in the second frame transmitted to the second STA.
- the first frame and the second frame are frames for transmitting different MPDUs.
- an integrated cache maintenance scheme is required to efficiently determine whether or not duplicate reception is performed. Otherwise, not only the frame transmitting STA but also the frame receiving STA must maintain both the cache managed based on the AID and the sequence number and the cache managed based on the MAC address and the sequence number, thereby increasing the cost of the STA. there is a problem.
- the same sequence number and different fragment number may be used for a specific STA. If the control information is managed, the sequence number based on the AID and the sequence number based on the MAC address are managed separately, but a malfunction may occur that cannot be handled correctly even if such duplicates are detected. It may be. Accordingly, in the present invention, for a frame including a compressed MAC header using STA AID, the STA MAC address identified by the STA AID (or mapped to STA AID) is sequenced. It is suggested to store the cache with the number.
- the sequence number of a frame to be transmitted is sequentially increased for each RA or for each ⁇ RA, access category ⁇ .
- the RA address field that is, the Address 1 field
- the sequence number of the transmitting STA may be determined by the AID of the receiving STA. Rather, it is managed based on the MAC address of the receiving STA. That is, the STA transmitting the frame stores (or caches) the last used sequence number for each MAC address of the receiving STA.
- the retry bit of the frame control field of the retransmitted frame is set to one.
- the STA AID included in the address field of the compressed MAC header is converted into a STA MAC address.
- the present invention proposes an encryption scheme for short MAC frames (or compressed MAC frames).
- the encryption scheme may be different with respect to a frame using a normal MAC header and a frame using a short MAC header.
- AAD additional authentication data
- a short MAC frame (or a short MAC header) cannot be used in retransmitting the same MPDU, and a normal MAC frame (or Normal MAC headers) to retransmit.
- the normal MAC frame (or a normal MAC header) cannot be used to retransmit the same MPDU, and a short MAC frame (or a short MAC header) can be used. Can be retransmitted.
- 18 is a block diagram illustrating CCMP encapsulation.
- Temporal Key Integrity Protocol (TKIP), Counter mode with Ci-block chaining Message authentication code Protocol (CCMP), and the like may be used.
- CCMP is proposed in the IEEE 802.11 standard and is an enhanced cryptographic encapsulation method designed for data confidentiality based on AES (Advanced Encryption Standard) CCM.
- a security mechanism in the IEEE 802.11 system may be provided for data frames and management frames. Specifically, data confidentiality, authentication, integrity, replay protection, and the like may be provided using TKIP, CCMP, and the like.
- an encrypted MPDU may be obtained from a payload of a plaintext MPDU.
- AAD for CCM may be configured using the fields of the MAC header of the original MPDU.
- the CCM algorithm may provide integrity protection for the fields included in the AAD.
- D is FCXFrame Control (MPD) field, Al (Address 1) field, A2 (Address 2) field, A3 (Address 3) field, SC (Sequence Control) field, A4 (Address 4) field, QC (QoS Control) field of MPDU. It may include.
- the CCM Nonce may be configured from the PN value, the A2 (Address 2) field of the MPDU, and the Priority value. Nonce means similar or bit string that is used only once in a security algorithm.
- An 8-oxup CCMP header is formed from the PN value and the Keyld value.
- TK temporary key
- AAD AAD
- Nonce AAD
- MPDU data ASD
- MIC Message Integrity Code
- FIG. 19 is a diagram illustrating an exemplary configuration of a frame control field of a short MAC header according to the present invention.
- Subfields of the frame control (FC) field of the short MAC header of FIG. 19 may be configured to be partially different from the subfields of the normal MAC header described with reference to FIG. 14.
- the Type field of the normal MAC header is 2 bits long, whereas the Type field has a 3 bits size in the FC field of the short MAC header.
- the Subtype field of the normal MAC header has a 4-bit size, whereas the Subtype field has a 3-bit size in the FC field of the short MAC header.
- the FC field of the short MAC header does not include the To DS field, the Retry field, and the Order field.
- the FC field of the short MAC header includes an EOSK End Of Serve field, a relayed frame field, and an Ack Pol i cy field.
- the FC field of the short MAC header includes a Protocol Vers ion field (2 bits), a Type field (3 bits), and a Subtype field. (3 bits), From DS field (1 bit), More Fragments field (1 bit), Power Management field (1 bit), More Data field (1 bit), Protected Frame field (1 bit), E0SP field (1 bit ), Relayed Frame field (1 bit), Ack Pol i cy field (1 bit).
- the AAD is configured using the fields of the MAC header.
- FIG. 20 a method for configuring AAD when the FC field of the short MAC header is used as shown in FIG. 19 is described with reference to FIG. 20.
- FIG. 20 illustrates an exemplary configuration of an AAD according to the present invention.
- the FC indicates a frame control field and may have a size of two octets.
- the FC field of the AAD of FIG. 20 may be configured according to the FC field of the short MAC header of FIG. 19.
- the Type bit of the FC field in the MD may be masked to 0 (Type bit masked to 0).
- the Power Management bit of the FC field in the AAD may be masked to 0 (Power Management bit masked to 0).
- the More Data bit of the FC field in the AAD may be masked to zero.
- the Protected Frame bit in the FC field in the MD may always be set to 1.
- the E0SP bit of the FC field in the AAD may be masked to zero.
- the relayed frame bit of the FC field in the AAD may be masked to zero.
- the FC field at AAD The Ack Pol i cy bit can be masked to zero. The meaning that a field is masked with a value of zero can be understood as the field being included in the AAD but not used.
- Al, A2, A3, and A4 in FIG. 20 refer to Address 1, Address 2, Address 3, and Address 4 fields of the MPDU, respectively.
- the A1 field may have a size of 6 octets or 2 octaves.
- the A2 field may have a size of 6 octets or 2 octets.
- the A3 field may have a size of six octets or zero octaves (ie may be omitted).
- the A4 field may have a size of 6 octets or may have a size of 0 octaves (ie may be omitted).
- the short MAC header omits one or more of the A3 or A4 fields, and the A1 (ie RA) and A2 (ie TA) fields are always It may be configured to include.
- the A1 field may have a size of 6 ox when it is configured with a MAC address or BSSID, and may have a size of 2 ox when it is configured with AID.
- the A2 field may have a size of 6 octets when configured with a MAC address or a BSSID, and may have a size of 2 octets when configured with an AID.
- one of the A3 and A4 fields or all of the A3 and A4 fields may be omitted in the AAD.
- AAD may consist of FC, A1, A2, A4, and SC; or, if A4 is omitted in the short MAC header, D is FC, Al, A2, A3 and SC.
- the AAD may consist of FC, Al, A2 and SC.
- the A1 field of the AAD may have a size of 6 octaves or 2 octaves.
- the A1 node of the AAD of FIG. 20 is configured according to the Address 1 field of the MPDU.
- the A1 field of the AAD may be configured with an A8x2 octet or a MAC address (6 octets) according to a frame direction (eg, an uplink frame or a downlink frame).
- a frame direction eg, an uplink frame or a downlink frame.
- the A1 field of the AAD is the AID of the receiver STA (2 Octet) value.
- the A1 field of the AAD is the receiver STA (or AP).
- MAC address or BSSID (6 octet) value is the receiver STA (or AP).
- the A2 field of the AAD may have a size of 6 octets or 2 octaves.
- the A2 field of the AAD of FIG. 20 is configured according to the Address 2 field of the MPDU.
- the A2 field of the AAD may include a frame direction (eg, an uplink frame or a downlink). Frame) may be configured as an AID (2 octets) or a MAC address (6 octets).
- a frame direction eg, an uplink frame or a downlink.
- Frame may be configured as an AID (2 octets) or a MAC address (6 octets).
- the From DS bit of the FC field of the short MAC header is set to 1 (in this case, the From DS bit of the FC field of the AAD is also set to the value 1)
- the A2 field of the AAD is the sender STA (or AP). It consists of a MAC address or BSSID (6 octets) value.
- the A2 field of the MD is the AID of the sender STA. 2 octaves) value.
- the A3 field of FIG. 20 is configured according to the Address 3 field of the MPDU, if present (i f present).
- the A4 field of FIG. 20 is configured according to the Address 4 field of the MPDU, if present (i f present).
- the SC of FIG. 20 indicates a sequence control field and may have a size of two octets.
- the SC field of the AAD of FIG. 20 may be configured according to the Sequence Control field of the MPDU.
- the Sequence Control field of the MAC header is composed of a Sequence Number and Fragment Number subfields
- the SC field of the AAD of FIG. 20 is also composed of a Sequence Number and Fragment Number subfields. do.
- the Sequence Number subfield (bits 4-15 of the Sequence Control field) of the SC field in AAD of FIG. 20 may be masked to zero.
- the Fragment Number subfield of the SC field in the AAD of FIG. 20 is not modified as compared to the Fragment Number subfield of the SC field of the MAC header (not modi f ied).
- Figure 21 shows an exemplary configuration of a Nonce according to the present invention.
- Nonce indicates a STA MAC Address ident if ied by A2 and a PN field identified by a Nonce Flags field, an A2 (Address 2) field. It may include.
- the Nonce Flags field may have a size of one octet.
- the STA MAC Address ident if ied by A2 field may have a size of 6 octets.
- the PN field may have a size of 6 octets.
- FIG. 21 further illustrates a specific configuration of the Nonce Flags field.
- the Nonce Flags field may consist of 4 bits for the Priority subfield, 1 bit for the Management subfield, and 3 bits reserved.
- the Priory ty field of the Nonce Flags of FIG. 21 may be set to a value indicating the priority of a short MAC frame.
- the Primary i ty field may be set to a value indicating a TID (Traf f i c Ident i ier) or an Access Category of a plain text MPDU.
- the Management field of the Nonce Flags of FIG. 21 may be set to a value indicating whether the plaintext MPDU is a management frame.
- the A2 field of Nonce of FIG. 21 may be configured according to the Address 2 field of the short MAC header.
- the A2 field of Nonce may be configured with a MAC address (6 oct) or an AIIX2 octet of the sender STA according to the frame direction (eg, an uplink frame or a downlink frame).
- the A2 field of the nonce may be configured as a MAC address or a BSSID (6 octet) value of the sender STA (or AP).
- the A2 field of Nonce may consist of the MAC address or BSSID (6 octet) value of the sender STA (or AP) identified by the A2 field of the short MAC header.
- the A2 field of Nonce may be configured with an AID (2 ox) value of the sender STA.
- the STA MAC Address ident if ied by A2 field of Nonce of FIG. 21 may be configured according to Address 2 of a short MAC header and may be determined according to a frame direction (eg, an uplink frame or a downlink frame). Can be. Specifically, in the case of an uplink frame, the STA MAC address of the sender STA identified by AIDC2 octet), and in the case of a downlink frame, the value of the BSSID included in A2, the STA MAC Address ident if ied by A2 field. The value of may be set.
- Figure 22 illustrates an exemplary configuration of an encrypted MPDU in accordance with the present invention.
- an encrypted MPDU corresponding to an encryption result for a plaintext MPDU includes a MAC header of FIG. 22 (the MAC header of the pl aintext MPDU of FIG. 18) and a CCMP header of FIG. 22 (in FIG. 18).
- CCMP header generated based on PN and Keyld), encrypted data generated in FIG. 22, MIC, and Frame Check Sequence (FCS).
- a temporary key is required to be updated every session, and a nonce value is unique every frame for a given temporary key. Required.
- a 48-bit PN (Packet Number) value is used, and the PN value is initialized every time the temporary key is updated.
- a PN value may be included in a CCMP header and transmitted.
- the CCMP header contains a six-octet (ie 48-bit) long PN field, referred to as six octets of PNO, PN1, PN2, PN3, PN4, and PN5.
- the present invention proposes to further reduce the MAC overhead for the encrypted PPDU by reducing the size of the PN field in a short MAC frame.
- the CCMP header includes only a part (eg, PN0 and PN1) of 6 octaves of the PN, and transmits the MAC frame with the rest (for example, PN2, PN3, PN4, and PN5). It can be synchronized between the STA and the receiving STA.
- the entirety of the 48-bit PN value may be transmitted using the normal MAC frame format instead of the short MAC frame format.
- a PN value of 48 bit size of an encrypted PPDU transmitted using the normal MAC frame format may be stored or maintained at the receiving STA. have. For example, for a PPDU that has been successfully received without error, successfully decrypted, and verified integrity, the cache for the set of ⁇ Transmitter Address, Temporal Key, PN 48 bytes] is sent to the receiving STA. Can be stored and maintained.
- the transmitting STA transmits a PPDU in which a short MAC frame is encrypted, which is a PPDU different from an encrypted PPDU previously transmitted through a normal MAC frame. can do.
- a part (eg, PN0 and PN1) of the 48-bit PN value may be included in the CCMP header included in the short MAC frame, thereby reducing the MAC overhead.
- the STA that receives the PPDU encrypting the short MAC frame may use a previously stored PN value to decrypt the short MAC frame. That is, when only the PN0 and the PN1 are included in the CCMP header of the short MAC frame, the remaining PN2, PN3, PN4, and PN5 may be configured with a total of 48 bits of PN values using the values stored in the receiving STA. . As described above, the decoding of the MAC frame is performed by using the 48-bit PN value formed by combining the part included in the CCMP header and the remaining part stored in the CCMP header (that is, the PN value configured by the combination is used in the Nonce configuration). It can be done.
- the receiving STA deletes the PN value stored in the set of ⁇ Transmitter Address, Temporal Key, PN 48 bits). Therefore, when the temporary key is changed, the transmitting STA does not use the short MAC frame format but must transmit the entire 48-bit PN value to the receiving STA using the normal MAC frame format. Through this, the PN value may be synchronized again between the transmitting and receiving STAs.
- the MAC header includes a Sequence Control field, the value of the Sequence Number subfield of the Sequence Control field is increased by one for each PPDU.
- the present invention proposes to further reduce the MAC overhead by using the value of Sequence Number as part of the PN value (or by relating the value of Sequence Number to part of the PN value).
- the first transmitted frame may inform the receiving STA of the entire PN value.
- the receiving STA may store the set of Sequence Number values of the Sequence Control field of the MAC header of the currently received frame while storing the entire PN value.
- the receiving STA may store and maintain a set of ⁇ Transmitter Address, Temporal Key, PN 48 bits, Sequence Number ⁇ in the cache. If a short MAC frame is used in subsequent transmission, the PN field may not be included in the CCMP header. In this case, the receiving STA may derive the PN value using the Sequence Number value of the Sequence Control field of the encrypted MPDU generated from the short MAC frame.
- the receiving STA deletes the PN value stored in the set of ⁇ Transmitter Address, Temporal Key, PN 48 bits, Sequence Number ⁇ . Therefore, when the temporary key is changed, the transmitting STA does not use the short MAC frame format and must transmit the entire 48-bit PN value to the receiving STA using the normal MAC frame format. Through this, the PN value may be synchronized again between the transmission and reception STAs.
- sequence number when used as part of the PN value, the sequence number may also be initialized and used as the temporary key is changed and the PN value is initialized.
- the sequence number is a part of the PN value, for example, PNO 1 1 PN1 (where I I operation means concatenat ion of PN0 and PN1) may correspond to a value of the Sequence Control field.
- the PN value may be calculated (or restored) as shown in Equation 1 below using Sequence Control (PNO I I PN1 corresponding to the SO field and PN2 to PN5 stored in the receiving terminal).
- Equation 1 PN2 I I PN3 I I PN4
- the STA sets the value of BPN (ie, PN2 II PN3) 1 PN4 II PN5) stored by the corresponding STA by 1; Increase.
- BPN ie, PN2 II PN3 1 PN4 II PN5
- FIG. 23 is a diagram to describe an MSDU reception flow in a MAC data plane structure.
- the STA that receives the MPDU may decompose it into individual MPDUs (De—aggregat ion).
- Val idat ion for verifying that the MPDU header and the CRC are valid for each MPDI] may be performed.
- the frame may be filtered whether the frame received by the STA is a frame transmitted for itself based on Address 1 (ie, a recipient address) included in the MAC header of the frame.
- Address 1 ie, a recipient address
- the MPDU decoding and integrity check are performed optionally if necessary (opt ional).
- Block ACK reordering is performed after decoding and integrity check are performed.
- Block ACK reordering means that MPDUs that have been successfully received are not considered to be immediately transmitted to a higher layer or higher MAC element for a plurality of MPDUs successfully received by a receiving STA, and considering MPDUs to be retransmitted later through a block ACK. This refers to the operation of buffering and managing until it is completely aligned according to the actual transmission order.
- Block ACK reordering for a plurality of frames is, for example, The sequence number values of the respective frames may be arranged in increasing order, and a frame corresponding to a sequence number already present in the Block ACK buffer may be discarded.
- defragment is an operation of restoring original information by combining a plurality of fragments.
- MSDU reception process is performed through integrity check and reporting on MSDU (opt ional), replay detection (in case of non-mesh STA), A-MSDU decomposition, rate limiting of received MSDU, etc. May proceed.
- the sequence number is rolled over.
- the BPN stored in the receiving STA ie, PN2
- the transmitting STA may aggregate a plurality of MPDUs, configure one A-MPDU, and then transmit the same to one PPDU. From the perspective of the STA receiving such a PPDU, Ack information is configured for each individual MPDU constituting the A-MPDU using a control frame called a Block ACK frame, and fed back to the transmitting STA.
- the transmitting STA that receives the feedback of the Block Ack frame performs retransmission for the MPDU indicated that an error has occurred.
- sequence numbers of the combined individual short MAC frames are N-2, N-1, N, 0, 1, and 2, respectively.
- an error occurred in short MAC frames having a sequence number corresponding to N and 0, and short MAC frames having a sequence number corresponding to N-2, N-1, 1, and 2 were successfully received without an error. Assume that
- the receiving STA performs MPDU decoding and integrity check before performing Block ACK reordering on the received short MAC frames (ie, regardless of the actual transmission order of the received frames).
- the sequence number In the process of processing a short MAC frame having 1 it is determined that a frame having a sequence number smaller than the sequence number of a previously received frame is received, and the BPN (ie, PN2
- the Sequence Control field is configured as part of the PN (for example, PNO II PN1) in the short MAC frame. Only when the MACDU decoding and integrity check operation is performed after the short MAC frames received through the Ack reordering are arranged in the order of actual transmission, if the Sequence Number is over-(ie, smaller than the previously received Sequence Number value).
- the BPN for example, PN2
- the same meaning may be used when the Block Ack is used or when the decoding is performed after Block Ack reordering, the Sequence Number of the received MPDU is assigned to the Sequence Number of the previously received MPDU.
- the BPN stored in the receiving STA for example, PN2 II PN3 II PN4 II PN5
- PN2 II PN3 II PN4 II PN5 may be defined as increasing by one.
- the Block ACK rearrangement buffer is generated by the MPDU that does not pass the integrity check (that is, the Integr i ty Check Failu) occurs. It may be updated incorrectly. In other words, whether or not to pass the integrity check during the Block ACK reordering operation, it is necessary to first store all MPDUs as already received in the Block ACK reordering buffer. Thereafter, the Integr i ty Check Fai lure causes retransmissions to that MPDU. If performed, the Block ACK reordering buffer may consider a frame duplicated with an MPDU previously received (ie, normally transmitted by the transmitting STA), and may cause a problem of discarding the MPDU.
- the execution order of the MPDU decoding and integrity check function is performed prior to the Block ACK reordering.
- the sequence numbers of the corresponding MPDUs roll over. MPDU transmissions must be performed so that there are no MPDUs waiting for an ack before they become available.
- sequence numbers of the combined individual short MAC frames are N-2, N-1, N, 0, 1, 2, respectively. Should not be allowed. That is, before the sequence number rolls over from N to 0, the restriction that the acknowledgment for the MPDU corresponding to the sequence numbers N-2 and N-1 should be received is applied.
- the transmitting STA can combine and transmit only short MAC frames corresponding to the sequence numbers N-2, N-1, and N, and transmit the sequence number only when no other MPDU waiting for ack exists in the transmitting STA.
- a short MAC frame with 0 can be transmitted.
- 24 is a flowchart for explaining a method according to an example of the present invention.
- the STA may receive a frame (eg, an MPDU).
- a frame eg, an MPDU
- the STA may determine a PN value by using a value of an SC field included in the received frame and a partial PN (or BPN) value stored in the STA.
- the STA may perform decoding on the frame using a PN value.
- an operation of increasing the partial PN (or BPN) value stored in the STA by 1 may be performed due to a-over of the value of the SC field.
- an operation of increasing the partial PN (or BPN) value stored in the STA by 1 due to a-over of the value of the SC field should not be performed.
- the partial PN (or BPN) value stored in the STA is increased by 1 due to the over-over of the SC field value regardless of the decoding and reordering of the block ACK.
- the operation can be performed.
- the example method described in FIG. 24 is represented by a series of operations for simplicity of description, but is not intended to limit the order in which the steps are performed, where each step is concurrent or in a different order if necessary. In addition, not all the steps illustrated in FIG. 24 are necessary to implement the method proposed by the present invention.
- 25 is a block diagram illustrating a configuration of a wireless device according to an embodiment of the present invention.
- the STA (IO) may include a processor 11, a memory 12, and a transceiver 13.
- the transceiver 13 may transmit / receive a radio signal and, for example, may implement a physical layer in accordance with the IEEE 802 system.
- the processor 11 may be connected to the transceiver 13 to implement a physical layer and / or a MAC layer according to the IEEE 802 system.
- the processor 11 may be configured to perform an operation according to the various embodiments of the present invention described above.
- modules for implementing the operations of the STA according to various embodiments of the present invention described above may be stored in the memory 12 and executed by the processor 11.
- the memory 12 may be included inside the processor 11 or installed outside the processor 11 and connected to the processor 11 by known means.
- the STA (IO) of FIG. 25 may be an AP STA or a non-AP STA.
- the processor 11 of the STA (IO) of FIG. 25 may be configured to control the transceiver 13 to receive an arbitrary frame.
- the processor 11 may be configured to determine the PN value by using a value of the SC field of the received frame and a partial PN (or BPN) value stored in the memory 12 of the processor.
- the processor 11 may be configured to perform decoding on the received frame using the determined PN value.
- the processor 11 determines the partial PN (or BPN) value stored in the STA due to the over-over of the value of the SC field.
- the operation of incrementing by 1 is limited to the case where the decoding is performed after the block ACK rearrangement.
- the specific configuration of the STA (IO) of FIG. 25 may be implemented so that the above-described matters described in various embodiments of the present invention may be independently applied or two or more embodiments may be applied at the same time. The description is omitted for the sake of brevity.
- embodiments of the present invention may be implemented through various means.
- embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.
- the method according to the embodiments of the present invention may include one or more ASICs (Appl icat ion Speci- fic Integrated Signals), DSPs CD Signal Signal Processors (DSPs), and Digital Signal Processing Devices (DSPDs). ), PLDs (Programmable Logic Devices), Field Programmable Gate Arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.
- ASICs Appl icat ion Speci- fic Integrated Signals
- DSPs CD Signal 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 modules, procedures, or functions for performing 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.
Abstract
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CN201480073052.XA CN105917597B (zh) | 2014-01-13 | 2014-07-04 | 无线lan系统中发送和接收支持短mac报头的帧的方法和装置 |
US15/111,165 US9826336B2 (en) | 2014-01-13 | 2014-07-04 | Method and apparatus for transmitting and receiving frame supporting short MAC header in wireless LAN system |
JP2016538034A JP6157746B2 (ja) | 2014-01-13 | 2014-07-04 | 無線lanシステムにおいて短いmacヘッダーを支援するフレームの送受信方法及び装置 |
KR1020167010397A KR101779436B1 (ko) | 2014-01-13 | 2014-07-04 | 무선랜 시스템에서 짧은 mac 헤더를 지원하는 프레임 송수신 방법 및 장치 |
EP14877812.9A EP3096467B1 (en) | 2014-01-13 | 2014-07-04 | Method and apparatus for transmitting and receiving frame supporting short mac header in wireless lan system |
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