Method and apparatus for accessing channel in wlan system
11 claims: 8 independent, 3 dependent
- 1無線通信システムの 少なくとも一つの ステーション(STA)でチャネルアクセスを行う方法であって、 前記方法は、 アクセスポイント(AP)からトラフィック指示マップ(TIM)要素及び制限されたアクセスウィンドウ(RAW)パラメータセット要素を含む第1フレームを受信する こと と、 前記RAWパラメータセット(RPS)要素に基づいて、前記STAのチャネルアクセス を 許容 する RAWを決定する こと と、 前記決定されたRAW内で前記APに第2フレームを伝送する こと と を含み、 前記RPS要素は 少なくとも一つ のRAW割当フィールドを含み、 前記 少なくとも一つ のRAW割当フィールドのそれぞれは、RAWグループ に関する情報 、RAW開始時点 に関する情報、クロススロット境界に関する情報 及びRAWデュレーション に関する情報 を含 み、前記RAWデュレーションは、スロットデュレーションと、前記RAWデュレーション内に含まれるスロットの個数との積に対応する、 方法。
- 2前記RAWグループ に関する情報 は、前記RAW内でチャネルアクセス の実行 が許容されるSTAの関連付け識別子(AID)を指示する、請求項1に記載 の方 法。
- 3前記STAがグループに属するか否かが、 前記RAWグループ に関する情報 によって指示される 、 請求項1に記載 の方 法。
- 4前記スロットデュレーション の値 は、前記RAW デュレーション 内 に含まれるスロットについて共通である 、請求項 1 に記載 の方 法。
- 5前記クロススロット境界 に関する情報 は、前記STA による 伝送がスロット境界を越え るこ とが許容されるか否かを指示する、請求項 1 に記載 の方 法。
- 6前記 少なくとも一つ のRAW割当フィールドのそれぞれは、ページングされたSTAのみに チャネル アクセスが制限されるか否かを示す 情報 をさらに含む、請求項1に記載 の方 法。
- 7前記STAは、前記RAW内でチャネルアクセスが許容される時点以前にドーズ状態で動作し、前 記時 点でアウェイク状態に変更される、請求項1に記載 の方 法。
- 8前記第1フレームはビーコンフレームである、請求項1に記載 の方 法。
- 9前記第2フレームは、Power Save(PS)-Pollフレームまたはトリガーフレームである、請求項1に記載 の方 法。
- 10前記第2フレームは、前記RAW内でEDCA(Enhanced Distributed Channel Access)に基づいて伝送される、請求項1に記載 の方 法。
- 11無線通信システムでチャネルアクセスを行うステーション(STA )で あって、 前記STAは、 送受信器と、 プロセッサと を備え、 前記プロセッサは、 アクセスポイン トか らトラフィック指示マップ(TIM)要素及び制限されたアクセスウィンドウ(RAW)パラメータセット要素を含む第1フレームを前記送受信器を用いて受信 することと、 前記RAWパラメータセット(RPS)要素に基づいて、前記STAのチャネルアクセス を 許容 する RAWを決定 することと、 前記決定されたRAW内で アクセスポイント( AP ) に第2フレームを前記送受信器を用いて伝送する ことと を行うように構成 され、 前記RPS要素は 少なくとも一つ のRAW割当フィールドを含み、 前記 少なくとも一つ のRAW割当フィールドのそれぞれは、RAWグループ に関する情報 、RAW開始時点 に関する情報、クロススロット境界に関する情報 及びRAWデュレーション に関する情報 を含 み、前記RAWデュレーションは、スロットデュレーションと、前記RAWデュレーション内に含まれるスロットの個数との積に対応する、STA 。
Independent claims11
200 paragraphs, as filed
The following description relates to a wireless communication system, and more specifically, to a method and an apparatus for accessing a channel in a wireless LAN system.
Recently, various wireless communication technologies have been developed with the development of information and communication technology. Among them, wireless LAN (WLAN) is a mobile phone such as a personal digital assistant (PDA), a laptop computer, or a portable multimedia player (PMP) based on wireless frequency technology. It is a technology that enables wireless access to the Internet at homes, companies, or areas where specific services are provided using personal digital assistants.
In order to overcome the limitation on communication speed, which has been pointed out as a weakness in wireless LAN , recent technical standards have introduced a system that increases the speed and reliability of the network and extends the operating distance of the wireless network. For example, IEEE 802.11n supports transmit and receive to support high processing rates (HT) with data processing speeds up to 540 Mbps or higher, and to minimize transmission errors and optimize data speeds. The application of MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas at both ends, has been introduced.
<p num="0004"> M2M (Machine-to-Machine) communication technology is being discussed as a next-generation communication technology. A technical standard for supporting M2M communication in IEEE 802.11 WLAN systems has also been developed as IEEE 802.11ah. In M2M communication, it is possible to consider a scenario in which a small amount of data is occasionally communicated at low speed in an environment where many devices exist.</p><p num="0005"> Communication in a wireless LAN system is performed on a medium shared by all devices. When the number of devices increases as in M2M communication, if it takes a lot of time to access the channel of one device, not only the overall system performance will deteriorate, but also the power saving of each device will be hindered. is there.</p><p num="0006"> It is a technical subject of the present invention to provide a new channel access plan capable of reducing the time required for channel access and reducing the power consumption of the device.</p><p num="0007"> The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned are the ordinary knowledge in the technical field to which the present invention belongs from the following description. Will be clearly understood by those who have.</p>
<p num="0008"> In order to solve the above technical problems, in the method of performing channel access at the station (STA) of the wireless communication system according to the embodiment of the present invention, the traffic instruction map (TIM) element and the limitation from the access point (AP). With the step of receiving the first frame containing the access window (RAW) parameter set element; and with the step of determining the RAW through which channel access of the STA is allowed based on the RAW parameter set (RPS) element; Including the step of transmitting the second frame to the AP in the determined RAW; the RPS element contains one or more RAW allocation fields, and each of the one or more RAW allocation fields is a RAW group field. , RAW start point field and RAW duration field can be included.</p><p num="0009"> In order to solve the above technical problems, a station (STA) device that performs channel access in a wireless communication system according to another embodiment of the present invention includes a transmitter / receiver and a processor, and the processor provides access. The first frame containing the traffic instruction map (TIM) element and the restricted access window (RAW) parameter set element is received from the point (AP) using the transmitter / receiver; based on the RAW parameter set (RPS) element. The STA is set to transmit a second frame to the AP using the transmitter / receiver within the determined RAW; the RPS element is one or more. Each of the one or more RAW assigned fields may include a RAW group field, a RAW start point field, and a RAW duration field, including a RAW assigned field.</p><p num="0010"> The following items can be commonly applied to the above examples according to the present invention.</p><p num="0011"> The RAW group field can indicate an association identifier (AID) of the STA that is allowed channel access within the RAW.</p><p num="0012"> It may be determined whether or not the STA belongs to the group indicated by the RAW group field.</p><p num="0013"> The RAW may include one or more slots.</p><p num="0014"> Each of the one or more RAW allocation fields may further include a slot duration field and a cross slot boundary field.</p><p num="0015"> The slot duration field can indicate the duration of one or more slots having the same value in the RAW.</p><p num="0016"> The cross-slot boundary field can indicate whether transmission of the STA is allowed to cross the slot boundary.</p><p num="0017"> Each of the one or more RAW assigned fields may further include a field indicating whether access is restricted only to the paged STA.</p><p num="0018"> The STA may operate in the dose state before the time when channel access is allowed in the RAW, and may be changed to the awake state when the channel access is allowed.</p><p num="0019"> The first frame may be a beacon frame.</p><p num="0020"> The second frame may be a Power Save (PS) -Poll frame or a trigger frame.</p><p num="0021"> The second frame may be transmitted in the RAW based on EDCA (Enhanced Distributed Channel Access).<u style="single"> The present specification also provides, for example, the following items.</u><u style="single">(Item 1)</u><u style="single"> A method of channel access at a station (STA) of a wireless communication system.</u><u style="single"> The step of receiving the first frame from the access point (AP) containing the traffic instruction map (TIM) element and the restricted access window (RAW) parameter set element, and</u><u style="single"> Based on the RAW parameter set (RPS) element, the step of determining the RAW that the STA channel access is allowed to be, and</u><u style="single"> Including a step of transmitting a second frame to the AP within the determined RAW.</u><u style="single"> A channel access method, wherein the RPS element includes one or more RAW allocation fields, each of which includes a RAW group field, a RAW start point field, and a RAW duration field.</u><u style="single">(Item 2)</u><u style="single"> The channel access method according to item 1, wherein the RAW group field indicates an association identifier (AID) of an STA in which channel access is permitted in the RAW.</u><u style="single">(Item 3)</u><u style="single"> The channel access method according to item 1, wherein it is determined whether or not the STA belongs to the group indicated by the RAW group field.</u><u style="single">(Item 4)</u><u style="single"> The channel access method according to item 1, wherein the RAW includes one or more slots.</u><u style="single">(Item 5)</u><u style="single"> The channel access method according to item 4, wherein each of the one or more RAW allocation fields further includes a slot duration field and a cross-slot boundary field.</u><u style="single">(Item 6)</u><u style="single"> The channel access method according to item 5, wherein the slot duration field indicates the duration of the one or more slots having the same value in the RAW.</u><u style="single">(Item 7)</u><u style="single"> The channel access method according to item 5, wherein the cross-slot boundary field indicates whether or not the transmission of the STA is allowed to cross the slot boundary.</u><u style="single">(Item 8)</u><u style="single"> The channel access method according to item 1, wherein each of the one or more RAW allocation fields further includes a field indicating whether access is restricted only to the paged STA.</u><u style="single">(Item 9)</u><u style="single"> The channel access method according to item 1, wherein the STA operates in a doze state before the time when channel access is allowed in the RAW, and is changed to an awake state when the channel access is allowed.</u><u style="single">(Item 10)</u><u style="single"> The channel access method according to item 1, wherein the first frame is a beacon frame.</u><u style="single">(Item 11)</u><u style="single"> The channel access method according to item 1, wherein the second frame is a Power Save (PS) -Poll frame or a trigger frame.</u><u style="single">(Item 12)</u><u style="single"> The channel access method according to item 1, wherein the second frame is transmitted in the RAW based on EDCA (Enhanced Distributed Channel Access).</u><u style="single">(Item 13)</u><u style="single"> A station (STA) device that provides channel access in a wireless communication system.</u><u style="single"> With the transmitter / receiver</u><u style="single"> Equipped with a processor</u><u style="single"> The processor receives a first frame from an access point (AP) containing a traffic instruction map (TIM) element and a restricted access window (RAW) parameter set element using the transmitter / receiver, and receives the RAW parameter set (RPS). Based on the) element, the RAW that allows channel access of the STA is determined, and the second frame is set to be transmitted to the AP using the transmitter / receiver within the determined RAW.</u><u style="single"> The RPS element includes one or more RAW allocation fields, each of which is a channel access execution STA device, including a RAW group field, a RAW start point field, and a RAW duration field.</u></p><p num="0022"> Both the general description described above and the detailed description below for the present invention are exemplary and are for further description of the claimed invention.</p>
<p num="0023"> In the present invention, by proposing a new channel access plan, it is possible to provide a method and an apparatus capable of reducing the time required for channel access and reducing the power consumption of the device.</p><p num="0024"> The effects obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned above are clearly understood by those having ordinary knowledge in the technical field to which the present invention belongs from the following description. Will be.</p>
The drawings attached herein are for the purpose of providing an understanding of the present invention, for showing various embodiments of the present invention, and for explaining the principles of the present invention together with the description of the specification.<figref num="1">It is a figure which shows the exemplary structure of the IEEE 802.11 system to which this invention is applied.</figref><figref num="2">It is a figure which shows the other exemplary structure of the IEEE 802.11 system to which this invention is applied.</figref><figref num="3">It is a figure which shows still another exemplary structure of the IEEE 802.11 system to which this invention is applied.</figref><figref num="4">It is a figure which shows the exemplary structure of the wireless LAN system.</figref><figref num="5">It is a figure for demonstrating the link setup process in a wireless LAN system.</figref><figref num="6">It is a figure for demonstrating the back-off process.</figref><figref num="7">It is a figure for demonstrating a hidden node and an exposed node.</figref><figref num="8">It is a figure for demonstrating RTS and CTS.</figref><figref num="9">It is a figure for demonstrating the power management operation.</figref><figref num="10">It is a figure for demonstrating the operation of STA which received TIM in detail.</figref><figref num="11">It is a figure for demonstrating the operation of STA which received TIM in detail.</figref><figref num="12">It is a figure for demonstrating the operation of STA which received TIM in detail.</figref><figref num="13">It is a figure for demonstrating group-based AID.</figref><figref num="14">It is a figure for demonstrating the existing TIM-based channel access method.</figref><figref num="15">It is a figure for demonstrating the basic concept of a slot-based channel access method.</figref><figref num="16">It is a figure which shows the exemplary format of RPS IE.</figref><figref num="17">It is a figure for demonstrating the structure of RAW which concerns on an example of this invention.</figref><figref num="18">It is a figure for demonstrating an example of the slot-based channel access which concerns on this invention.</figref><figref num="19">It is a figure for demonstrating another example of the slot-based channel access which concerns on this invention.</figref><figref num="20">It is a figure for demonstrating the multicast / broadcast slot allocation in RAW which concerns on an example of this invention.</figref><figref num="21">It is a figure for demonstrating the multicast / broadcast slot allocation in RAW which concerns on another example of this invention.</figref><figref num="22">It is a figure for demonstrating the channel access method which concerns on an example of this invention.</figref><figref num="23">It is a block diagram which shows the structure of the wireless device which concerns on one Example of this invention.</figref>
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description disclosed below, along with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and does not represent the only embodiment in which the invention can be practiced. The following detailed description includes specific details to provide a complete understanding of the present invention. However, those skilled in the art will appreciate that the present invention is feasible without those specific details.
Each of the following examples is a combination of each component and feature of the present invention in a predetermined form. Each component or feature may be considered as selective unless otherwise specified. Each component or feature can be implemented in a form that is not combined with other components or features. In addition, some components and / or features may be combined to form an embodiment of the present invention. The order of operations described in each embodiment of the present invention can be changed. Some configurations or features of one embodiment may be included in another embodiment or may be replaced by the corresponding configurations or features of another embodiment.
The specific terms used in the following description are provided to aid the understanding of the present invention, and the use of these specific terms may be changed to other forms without departing from the technical idea of the present invention. Is.
In some cases, in order to avoid obscuring the concept of the present invention, known structures and devices may be omitted or illustrated in the form of a block diagram centered on the core functions of each structure and device. In addition, the same components will be described with reference to the same drawing reference throughout the present specification.
The embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802 system, 3GPP system, 3GPP LTE and LTE-A (LTE-Advanced) system, and 3GPP2 system. it can. That is, in the examples of the present invention, the steps or parts where the explanation is omitted in order to clarify the technical idea of the present invention can be supported by the above-mentioned documents. In addition, all the terms disclosed in this document can be explained by the above standard documents.
The following technologies include CDMA (Code Division Multiple Access), FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access), SC-FDMA (Single Carrier Frequency Division Multiple Access), etc. It can be used for various wireless access systems such as. CDMA can be embodied by radio technology such as UTRA (Universal Terrestrial Radio Access) and CDMA2000. TDMA is GSM (registered trademark) (Global System for Mobile communications) / GPRS (General Packet Radio Service) / EDGE (Enhanced) It can be embodied by wireless technologies such as Data Rates for GSM® Evolution). OFDMA can be embodied by wireless technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and E-UTRA (Evolved UTRA). For the sake of clarity, the IEEE 802.11 system will be mainly described below, but the technical idea of the present invention is not limited thereto.
(WLAN system structure) 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 can be composed of multiple components, and these interactions can provide a WLAN that supports transparent mobility to the upper layers. The Basic Service Set (BSS) can be a basic building block in an IEEE 802.11 LAN. In Figure 1, there are two BSSs (BSS1 and BSS2), and two STAs are included as members of each BSS (STA1 and STA2 are included in BSS1, and STA3 and STA4 are included in BSS2). Is shown as an example. In FIG. 1, the ellipse indicating the BSS may be understood to indicate the coverage area in which the STA contained in the BSS maintains communication. This area can be called BSA (Basic Service Area). When a STA moves out of the BSA, it will not be able to communicate directly with other STAs within that BSA.
The most basic type of BSS in an IEEE 802.11 LAN is an independent BSS (IBSS). For example, IBSS can have a minimal form consisting of only two STAs. Further, the BSS (BSS1 or BSS2) in FIG. 1, which is the simplest form and omits other components, may correspond to a typical example of IBSS. Such a configuration is possible when the STAs can communicate directly with each other. Further, such a form of LAN is not configured in advance, but is configured when LAN is required, and this can also be called an ad-hoc network.
STA membership in BSS may change dynamically as STAs turn on and off, and STAs enter and exit the BSS area of STAs. To become a member of BSS, STAs can join BSS using a synchronization process. In order to access all services of the BSS infrastructure, the STA must be associated with the BSS. Such associations can be set dynamically and can include the use of Distribution System Service (DSS).
FIG. 2 is a diagram showing another exemplary structure of an IEEE 802.11 system to which the present invention can be applied. FIG. 2 shows a form in which components such as a distribution system (Distribution System; DS), a distribution system medium (DSM), and an access point (AP) are added to the structure of FIG.
The direct station-to-station distance in the LAN may be limited by PHY performance. In some cases, such distance limits are sufficient, but in some cases communication between stations at greater distances may be required. A distribution system (DS) can be configured to support extended coverage.
DS means a structure in which BSSs are interconnected with each other. Specifically, instead of the BSSs existing independently as shown in FIG. 1, the BSSs may exist as a component of an extended form of a network composed of a plurality of BSSs.
DS is a logical concept and can be identified by the characteristics of the distribution system medium (DSM). In this regard, the IEEE 802.11 standard makes a logical distinction between wireless medium (WM) and distribution system medium (DSM). Each logical medium is used for different purposes and is used by different components. The definition of the IEEE 802.11 standard does not limit such media to being identical or different from each other. The flexibility of the IEEE 802.11 LAN structure (DS structure or other network structure) can be explained in that the plurality of media are logically different from each other in this way. That is, the IEEE 802.11 LAN structure can be embodied in various ways, and the LAN structure can be independently specified by the physical characteristics of each embodied example.
The DS can provide seamless integration of multiple BSSs and assist the transfer synchronizer by providing the logical services needed to handle addresses to destinations.
AP means an individual having STA functionality and allowing access to the DS through WM for each associated STA. Data can be moved between BSS and DS through AP. For example, STA2 and STA3 shown in FIG. 2 have the functionality of STA and provide the function of allowing each associated STA (STA1 and STA4) to access the DS. Also, since any AP basically corresponds to STA, each AP is an addressable individual. The address used by the AP for communication on the WM and the address used by the AP for communication on the DSM do not necessarily have to be the same.
Data transmitted from any one of the STAs associated with an AP to the STA address of that AP may always be received on an uncontrolled port and processed by an IEEE 802.1X port access individual. Also, once the controlled port is authenticated, the transmitted data (or frame) may be transmitted to the DS.
FIG. 3 shows yet another exemplary structure of an IEEE 802.11 system to which the present invention can be applied. Figure 3 conceptually shows an Extended Service Set (ESS) to provide even greater coverage for the structure in Figure 2.
Radio networks of arbitrary size and complexity may consist of DS and BSS. In the IEEE 802.11 system, such a network is called an ESS network. ESS can correspond to a set of BSS connected to one DS. However, ESS does not include DS. The feature of the ESS network is that it can be seen as an IBSS network at the LLC (Logical Link Control) layer. The STAs contained in the ESS can communicate with each other, and the mobile STA can transparently move from one BSS to another (within the same ESS) to LLC.
IEEE 802.11 makes no assumptions about the relative physical location of the BSS in Figure 3, and any of the following forms are possible: BSS may partially overlap, which is a commonly used form to provide continuous coverage. In addition, the BSSs do not have to be physically connected, and logically there is no limit to the distance between the BSSs. Also, the BSSs can be physically located in the same position, which can be used to provide redundancy. Also, one (or one or more) IBSS or ESS networks can physically exist in the same space as one (or one or more) ESS networks. This can be the case if the ad-hook network operates where the ESS network resides, if different organizations form physically overlapping IEEE 802.11 networks, or if two or more are different from each other at the same location. It may correspond to the ESS network form when access and security policies are required.
FIG. 4 is a diagram showing an exemplary structure of a wireless LAN system. FIG. 4 shows an example of the base structure BSS including the DS.
In the example of FIG. 4, BSS1 and BSS2 constitute ESS. In a wireless LAN system, STA is a device that operates in accordance with the MAC / PHY regulations of IEEE 802.11. STAs include AP STAs and non-AP STAs. Non-AP STA corresponds to devices that users generally handle directly, such as laptop computers and mobile phones. In the example of FIG. 4, STA1, STA3, and STA4 correspond to non-AP STA, and STA2 and STA5 correspond to AP STA.
In the following description, the non-AP STA is a terminal, a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), and a mobile terminal (MS). It can also be called a Mobile Terminal, a Mobile Subscriber Station (MSS), and so on. APs are also base stations (BS), node-B (Node-B), advanced node-B (evolved Node-B; eNB), and base transmission / reception systems (Base Transceiver System) in other wireless communication fields. ; BTS), Femto BS), etc.
(Link setup process) FIG. 5 is a diagram for explaining a general link setup process.
In order for the STA to set up a link to a network and send and receive data, it first discovers the network, authenticates it, establishes an association, and secures it. ), Etc. must be performed. The link setup process can also be called the session start process or session setup process. In addition, the process of discovery, authentication, association, and security setting in the link setup process can be collectively called the association process.
An exemplary link setup process will be described with reference to FIG.
In step S510, the STA can perform a network discovery operation. Network discovery operations can include STA scanning operations. That is, in order for the STA to access the network, it must search for a network in which it can participate. The STA must identify compatible networks before joining a wireless network, and the process of identifying a network that exists in a specific area is called scanning.
Scanning methods include active scanning and passive scanning.
FIG. 5 shows a network discovery operation including an active scanning process as an example. In active scanning, the scanning STA transmits a probe request frame to search for which APs are present in the vicinity while moving channels, and waits for a response to the probe request frame. The responder transmits a probe response frame to the STA that transmitted the probe request frame as a response to the probe request frame. Here, the responder is the last beacon in the BSS of the scanned channel. It can be the STA that transmitted frame). In BSS, the AP transmits the beacon frame, so the AP becomes the responder, and in IBSS, the STAs in the IBSS alternately transmit the beacon frame, so that the responder is not constant. For example, a STA that transmits a probe request frame on channel 1 and receives a probe response frame on channel 1 stores the BSS-related information contained in the received probe response frame and stores the BSS-related information contained in the received probe response frame on the next channel (for example, channel 2). You can go to the channel) and scan in the same way (ie, send and receive probe requests / responses on channel 2).
Although not shown in FIG. 5, the scanning operation may be performed by a passive scanning method. In passive scanning, the scanning STA waits for a beacon frame while moving channels. The beacon frame is one of the management frames in IEEE 802.11, and is transmitted periodically so that the scanning STA can search for the wireless network and join the wireless network by notifying the existence of the wireless network. To. In BSS, the AP plays a role of periodically transmitting the beacon frame, and in IBSS, the STAs in the IBSS alternately transmit the beacon frame. When the scanning STA receives the beacon frame, it stores the information about the BSS contained in the beacon frame and records the beacon frame information in each channel while moving to another channel. The STA that received the beacon frame can store the BSS-related information contained in the received beacon frame, move to the next channel, and perform scanning on the next channel in the same way.
Comparing active scanning with passive scanning has the advantage that active scanning has less delay and power consumption than passive scanning.
After the STA discovers the network, the authentication process can be performed in step S520. Such an authentication process can be referred to as a first authentication process in order to clearly distinguish it from the security setup operation of step S540 described later.
The authentication process includes a process in which the STA sends an authentication request frame to the AP, and in response, the AP sends an authentication response frame to the STA. The authentication frame used for authentication request / response corresponds to the management frame.
Authentication frames include authentication algorithm number, authentication transaction sequence number, status code, challenge text, RSN (Robust Security Network), and Finite. It can contain information about Cyclic Group) and so on. This is just an example of the information that can be included in the authentication request / response frame and may be replaced by other information or may further include additional information.
The STA can send an authentication request frame to the AP. The AP can decide whether to allow authentication for the STA based on the information contained in the received authentication request frame. The AP can provide the result of the authentication process to the STA through the authentication response frame.
After the STA has been successfully authenticated, the association process can be performed in step S530. The association process includes the process in which the STA transmits an association request frame to the AP, and in response the AP transmits an association response frame to the STA.
For example, an association request frame can be information about various capabilities, beacon listening interval, SSID (service set identifier), supported rates, supported channels, RSN, mobile domain. , Supported operating classes, TIM Traffic Indication Map Broadcast request, interworking service capability, etc. can be included.
For example, the association response frame includes information on various capabilities, status code, AID (Association ID), support rate, EDCA (Enhanced Distributed Channel Access) parameter set, RCPI (Received Channel Power Indicator), and RSNI (Received Signal to Noise Indicator). ), Mobility domain, timeout interval (association comeback time), overlapping BSS scan parameters, TIM broadcast response, QoS map, and other information can be included.
This is just one example of the information that can be included in the association request / response frame and may be replaced by other information or may contain additional information.
After the STA has been successfully associated with the network, the security setup process can be performed in step S540. The security setup process of step S540 can be said to be an authentication process through an RSNA (Robust Security Network Association) request / response. The authentication process of step S520 described above is set as the first authentication process, and the security of step S540 is performed. The setup process can also be simply called the authentication process.
The security setup process of step S540 can include, for example, performing a private key setup through 4-way handshaking through an Extensible Authentication Protocol over LAN (EAPOL) frame. In addition, the security setup process may be performed by a security method not defined by the IEEE 802.11 standard.
(Evolution of WLAN) IEEE 802.11n is a relatively recently established technical standard for overcoming the limits of communication speed in wireless LAN. IEEE 802.11n aims to increase the speed and reliability of networks and extend the operating range of wireless networks. More specifically, IEEE 802.11n supports high throughput (HT) with data processing speeds up to 540 Mbps and above, and also at the transmit end to minimize transmission errors and optimize data speed. It is based on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas at both the receiving end and the receiving end.
With the spread of wireless LAN and the diversification of applications using it, recently, a new wireless LAN system for supporting a processing rate higher than the data processing speed supported by IEEE 802.11n. The need for is emerging. The next-generation wireless LAN system that supports Very High Throughput (VHT) is the next version of the IEEE 802.11n wireless LAN system (eg, IEEE 802.11ac), which is the MAC Service Access Point. ; SAP) is one of the newly proposed IEEE 802.11 wireless LAN systems to support data processing speeds of 1 Gbps or higher.
The next-generation wireless LAN system supports MU-MIMO (Multi User Multiple Input Multiple Output) transmission in which multiple STAs access the channel at the same time in order to use the wireless channel efficiently. The MU-MIMO transmission scheme allows APs to simultaneously transmit packets to one or more MIMO paired STAs.
It is also being discussed to support the operation of wireless LAN systems in white space. For example, the introduction of wireless LAN systems in the TV white space (TV WS), such as the idle frequency band (eg, 54-698 MHz band) due to the digitization of analog TV, is being discussed as the IEEE 802.11af standard. However, this is only an example, and the white space can be said to be a permitted band that can be preferentially used by a licensed user. An authorized user means a user who is authorized to use the authorized bandwidth, and is called an authorized device, a primary user, an incumbent user, and the like. You can also.
For example, APs and / or STAs running on WS must provide protection for authorized users. For example, if a specific WS channel, which is a frequency band divided by regulation so as to have a specific bandwidth in the WS band, is already in use by an authorized user such as a microphone, it is permitted. In order to protect the user, AP and / or STA cannot use the frequency band corresponding to the WS channel. In addition, APs and / or STAs must discontinue use of the frequency band currently used for frame transmission and / or reception when authorized users use it.
Therefore, the AP and / or STA must precede the procedure for ascertaining whether or not a specific frequency band within the WS band can be used, that is, whether or not there is an authorized user in that frequency band. Must be. Knowing whether an authorized user is in a specific frequency band is called spectral sensing. As the spectrum sensing mechanism, an energy detection method, a signature detection method, or the like is utilized. If the strength of the received signal is above a certain value, it is determined that the authorized user is in use, and if a DTV preamble is detected, it is determined that the authorized user is in use. Can be done.
In addition, M2M (Machine-to-Machine) communication technology is being discussed as a next-generation communication technology. A technical standard for supporting M2M communication in IEEE 802.11 wireless LAN systems has been developed as IEEE 802.11ah. M2M communication means a communication method including one or more machines, and is sometimes called MTC (Machine Type Communication) or thing communication. Here, a machine means an entity that does not require direct human manipulation or intervention. For example, not only devices such as meter detectors and vending machines equipped with wireless communication modules, but also users such as smartphones that can automatically connect to a network and communicate without user operation / intervention. The device may also fall under the example of a machine. M2M communication can include communication between devices (eg, D2D (Device-to-Device) communication), communication between a device and an application server, and the like. Examples of communication between devices and servers include vending machines and servers, and POS (Point). of Sale) Communication between equipment and server, electricity, gas or water meter detector and server. Other M2M communication-based applications may include security, transportation, health care, and the like. Considering the characteristics of such application examples, in general, M2M communication must be able to support the occasional transmission and reception of a small amount of data at low speed in an environment where a large number of devices exist.
Specifically, M2M communication must be able to support a large number of STAs. In the currently defined wireless LAN system, it is assumed that a maximum of 2007 STAs are associated with one AP, but in M2M communication, a larger number (about 6000) of STAs are associated with one AP. There are discussions on ways to help if this is the case. Also, in M2M communication, it is expected that there are many applications that support / request low transmission speeds. To support this smoothly, for example, in a wireless LAN system, the STA can recognize the presence or absence of data transmitted to itself based on the TIM (Traffic Indication Map) element, but there is a way to reduce the bitmap size of the TIM. It is being discussed. Also, in M2M communication, it is expected that there will be a lot of traffic with a very long transmission / reception interval. For example, it is required to exchange a very small amount of data every long cycle (for example, one month) such as electricity / gas / water usage. Also, in M2M communication, downlink (ie, AP to non-AP) A structure in which the STA behaves in response to instructions provided via the STA), resulting in data being reported via the uplink (ie, the non-AP STA to AP link). Since it has, M2M communication mainly deals with improved communication methods on the uplink where the main data is transmitted. In addition, since M2M STA mainly operates on a battery and is often difficult for the user to charge well, it is required to ensure a long life by minimizing battery consumption. In addition, M2M STA is expected to be difficult for users to operate directly in specific situations, so it is required to have a function to recover by itself. Therefore, in a wireless LAN system, even if the number of STAs that can be associated with one AP is very large, the number of STAs that have data frames received from the AP during one beacon cycle is very small. Plans are being discussed to help efficiently and reduce STA power consumption.
Thus, wireless LAN technology is evolving rapidly, in addition to the above examples, direct link setup, improved media streaming performance, support for high speed and / or large initial session setup, extended bandwidth and Technologies for supporting operating frequencies have been developed.
(WLAN operating below 1GHz (sub-1GHz)) As mentioned earlier, the IEEE 802.11ah standard is under discussion with M2M communication as a use case. The IEEE 802.11ah standard operates in the unlicensed band, excluding the TV white space band, at operating frequencies below 1 GHz (sub-1 GHz) and primarily supports existing indoor coverage. It can have a much wider coverage (for example, up to 1km) than the WLAN that was used. That is, unlike the existing WLANs operating at 2.4GHz and 5GHz frequencies, when WLANs are used in the operating frequency band of sub-1GHz (for example, 700 to 900MHz), they are the same due to the propagation characteristics of that band. AP coverage is extended approximately 2-3 times in transmission power. In this case, it has a feature that a very large number of STAs can be connected per AP. Table 1 below summarizes the use cases considered by the IEEE 802.11ah standard.
<tables num="1"><img id="000002" he="78" wi="141" file="JP5961749B2_D0001.tif" img-format="tif" img-content="drawing" /></tables> According to Use Case 1 in Table 1 above, various types of sensor / meter devices can be connected to 802.11ah APs for M2M communication. In particular, in the case of a smart grid, up to 6,000 sensor / meter devices can be connected to a single AP.
According to Use Case 2 in Table 1 above, an 802.11ah AP that provides wide coverage acts as a backhaul link for other systems such as IEEE 802.15.4g.
According to Use Case 3 in Table 1 above, an extended range of outdoor areas such as Extended home coverage, Campus wide coverage, and Shopping malls. Hotspot (outdoor extended range hotspot) Communication can be assisted. According to Use Case 3, 802.11ah APs can also serve to distribute the overload of cellular traffic by supporting traffic offloading of cellular mobile communications.
Such a physical layer (PHY) configuration for communication in the sub-1 GHz band can be realized by down-clocking the existing IEEE 802.11ac PHY. In this case, the 20/40/80/160/80 + 80MHz channel bandwidth on 802.11ac is 2/4/8/16/8 + 8MHz channel in the sub-1GHz band through 1/10 downclocking. Bandwidth can be provided. As a result, the guard interval (GI) increases 10-fold from 0.8 μs to 8 μs. Table 2 below compares the throughput of the 802.11ac PHY and the 1/10 downclocked sub-1GHz PHY.
<tables num="2"><img id="000003" he="45" wi="159" file="JP5961749B2_D0001.tif" img-format="tif" img-content="drawing" /></tables> (Media access mechanism) In a wireless LAN system based on IEEE 802.11, the basic access mechanism of MAC (Medium Access Control) is the CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism. The CSMA / CA mechanism, also known as the IEEE 802.11 MAC Distributed Coordination Function (DCF), basically employs a "listen before talk" access mechanism. According to these types of access mechanisms, APs and / or STAs have a radio channel or medium during a predetermined time interval (eg, DIFS (DCF Inter-Frame Space)) prior to initiating transmission. CCA (Clear Channel Assessment) can be performed. As a result of sensing, the medium is idle. If it is determined to be status), frame transmission is started through the medium. On the other hand, when the medium is perceived as occupied status, the AP and / or STA does not start its own transmission and a delay period for media access (eg, a random backoff period). After setting)) and waiting, frame transmission can be attempted. By applying an arbitrary backoff cycle, multiple STAs are expected to try frame transmission after waiting different times, thus minimizing collisions.
The IEEE 802.11 MAC protocol also provides HCF (Hybrid Coordination Function). HCF is based on DCF and PCF (Point Coordination Function). PCF is a polling-based synchronous access method that periodically polls all receiving APs and / or STAs so that they can receive data frames. In addition, HCF has EDCA (Enhanced Distributed Channel Access) and HCCA (HCF Controlled Channel Access). EDCA is a competition-based access method for providers to provide data frames to multiple users, and HCCA is a non-competitive channel access method that uses a polling mechanism. is there. HCF also includes a medium access mechanism to improve WLAN quality of service (QoS), and contention. QoS data can be transmitted in both Period (CP) and Non-Competitive Period (CFP).
FIG. 6 is a diagram for explaining the backoff process.
The operation based on an arbitrary backoff cycle will be described with reference to FIG. When the medium that was in the occupied (occupy or busy) state is changed to the idle (idle) state, multiple STAs can attempt data (or frame) transmission. At this time, as a measure for minimizing the collision, the STA can select an arbitrary back-off count, wait for the corresponding slot time, and then try the transmission. Any backoff count has a pseudo-random integer value and can be determined by any one of the values in the range 0 to CW. Where CW is the contention window Window) Parameter value. CWmin is given as the initial value of the CW parameter, but it can be doubled in the case of transmission failure (for example, when ACK for the transmitted frame cannot be received). When the CW parameter value reaches CWmax, data transmission can be attempted while maintaining the CWmax value until the data transmission is successful, and when the data transmission is successful, the data is reset to the CWmin value. The CW, CWmin and CWmax values are preferably set to 2n-1 (n = 0,1,2, ...).
When any backoff process begins, the STA continues to monitor the medium while counting down the backoff slot according to the determined backoff count value. When the medium is monitored as occupied, the countdown is stopped and waits, and when the medium becomes idle, the remaining countdown is restarted.
In the example of FIG. 6, when a packet to be transmitted to the MAC of STA3 arrives, STA3 confirms that the medium is idle only by DIFS, and can immediately transmit the frame. On the other hand, the remaining STAs monitor that the medium is busy and wait. In the meantime, data to be transmitted may also be generated in each of STA1, STA2 and STA5, and each STA waits for DIFS when the medium is monitored as idle, and then each selected arbitrary backoff count value. The backoff slot can be counted down according to the above. In the example of FIG. 6, STA2 selects the smallest backoff count value, and STA1 selects the largest backoff count value. That is, the case where the residual backoff time of STA5 is shorter than the residual backoff time of STA1 at the time when STA2 finishes the backoff count and starts frame transmission is illustrated. STA1 and STA5 stop the countdown for a while and wait while STA2 occupies the medium. When the occupation of STA2 is completed and the medium becomes idle again, STA1 and STA5 wait for DIFS and then resume the back-off count that has been stopped. That is, frame transmission can be started after counting down the remaining backoff slots for the remaining backoff time. Since the residual backoff time of STA5 was shorter than that of STA1, STA5 started frame transmission. On the other hand, while STA2 occupies the medium, data to be transmitted may also be generated in STA4. At this time, from the standpoint of STA4, when the medium becomes idle, only DIFS is waited, and then a countdown is performed by an arbitrary backoff count value selected by itself, and frame transmission can be started. The example in FIG. 6 shows a case where the residual backoff time of STA5 coincides with an arbitrary backoff count value of STA4 by chance, in which case a collision may occur between STA4 and STA5. In case of collision, both STA4 and STA5 are A Data transmission will fail because CK cannot be received. In this case, STA4 and STA5 can count down by doubling the CW value and then selecting any backoff count value. On the other hand, STA1 can wait while the medium is occupied by the transmission of STA4 and STA5, wait for DIFS when the medium becomes idle, and then start frame transmission when the remaining backoff time elapses. ..
(STA sensing operation) As mentioned above, the CSMA / CA mechanism includes virtual carrier sensing as well as physical carrier sensing in which the AP and / or STA directly sense the medium. Virtual carrier sensing is used to complement problems that can occur with medium access, such as hidden node problems. For virtual carrier sensing, the MAC of the wireless LAN system is the network allocation vector (Network Allocation). Vector; NAV) can be used. The NAV indicates to other APs and / or STAs how long the AP and / or STA currently using or authorized to use the medium remains until the medium is ready for use. It is a value to be used. Therefore, the value set in NAV corresponds to the 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 has media access (or) during the period. Channel access) is prohibited or deferred. The NAV may be set, for example, by the value in the "duration" field of the frame's MAC header.
In addition, a robust collision detect mechanism has been introduced to reduce the possibility of collision. This will be described with reference to FIGS. 7 and 8. Actually, the carrier sensing range and the transmission range may not be the same, but for convenience of explanation, it is assumed that they are the same.
FIG. 7 is a diagram for explaining hidden nodes and exposed nodes.
Figure 7 (a) is an example of a hidden node, where STA A and STA B are in communication and have information that STA C sends. Specifically, even though STA A is sending information to STA B, when STA C performs carrier sensing before sending data to STA B, it determines that the medium is idle. Sometimes. This is because the transmission of STA A (that is, medium occupancy) may not be sensed at the position of STA C. In such a case, STA B receives the information of STA A and STA C at the same time, so that a collision will occur. At this time, STA A can be said to be a hidden node of STA C.
Figure 7 (b) is an example of an exposed node, where STA B is transmitting data to STA A and STA C has the information to transmit to STA D. is there. In this case, when STA C performs carrier sensing, it may be determined that the medium is occupied by the transmission of STA B. Therefore, even if STA C has the information to be transmitted to STA D, it is sensed that the medium is occupied, so it is necessary to wait until the medium becomes idle. However, since STA A is actually outside the transmission range of STA C, transmission from STA C and transmission from STA B may not collide from the standpoint of STA A, so STA C is STA B. It will wait unnecessarily until the transmission is stopped. At this time, STA C can be said to be an exposed node of STA B.
FIG. 8 is a diagram for explaining RTS and CTS.
In order to effectively utilize the collision avoidance mechanism in the exemplary situation shown in Figure 7, short signaling packets such as RTS (request to send) and CTS (clear to send) are used. It can be used. The RTS / CTS between the two STAs can allow the surrounding STAs to overhear, and allow the surrounding STAs to consider whether or not information is transmitted between the two STAs. For example, if the STA that is trying to transmit data transmits an RTS frame to the STA that receives the data, the STA that receives the data can notify itself that it will receive the data by transmitting the CTS frame to the surrounding STAs. ..
Figure 8 (a) is an example of how to solve the hidden node problem, assuming that both STA A and STA C try to transmit data to STA B. 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 between STA A and STA B is completed to avoid collision.
Figure 8 (b) is an example of how to solve the exposed node problem, where STA C overhears the RTS / CTS transmission between STA A and STA B, causing STA C to self-other. It can be determined that no collision occurs even if data is transmitted to STA (for example, STA D). That is, STA B transmits RTS to all surrounding STAs, and only STA A, which has the data actually sent, transmits CTS. Since STA C can only receive RTS but not STA A's CTS, it can be seen that STA A is outside the carrier sensing of STA C.
(Power management) As mentioned above, in a wireless LAN system, channel sensing must be performed before the STA transmits and receives, but constant sensing of the channel causes continuous power consumption of the STA. The power consumption in the receiving state is not much different from the power consumption in the transmitting state, and maintaining the receiving state also imposes a heavy burden on the power-limited (that is, battery-powered) STA. Therefore, if the STA maintains the reception standby state in order to continuously sense the channel, the power will be consumed inefficiently without any special advantage in terms of the wireless LAN processing rate. To solve these problems, the wireless LAN system supports STA's power management (PM) mode.
The power management mode of STA is divided into active mode and power save (PS) mode. STA basically operates in active mode. STAs operating in active mode maintain an awake state. The awake state is a state in which normal operations such as frame transmission / reception and channel scanning are possible. On the other hand, the STA operating in the PS mode operates while switching between the sleep state (or the doze state) and the awake state (awake state). The STA, which operates in sleep mode, operates with minimal power and does not perform channel scanning as well as frame transmission / reception.
The longer the STA operates in sleep mode, the less power it consumes and thus the longer the STA operates. However, since frame transmission / reception is not possible in the sleep state, it cannot operate unconditionally for a long time. If the STA operating in the sleep state has a frame to be transmitted to the AP, it can switch to the awake state and transmit the frame. On the other hand, if there is a frame transmitted by the AP to the STA, the sleeping STA cannot receive it, and it cannot be grasped that there is a frame to be received. Therefore, the STA may need to switch to the awake state according to a specific cycle in order to confirm the existence of the frame transmitted to itself (and to receive it if it exists).
FIG. 9 is a diagram for explaining the power management operation.
Referring to FIG. 9, the AP 210 transmits a beacon frame to the STA in the BSS at regular intervals (S211, S212, S213, S214, S215, S216). The beacon frame contains a TIM (Traffic Indication Map) information element (Information Element). The TIM information element contains information that tells AP 210 that there is buffered traffic to the STA associated with it and that it will carry a frame. The TIM element includes a TIM used to notify a unicast frame and a DTIM (delivery traffic indication map) used to notify a multicast or broadcast frame.
The AP 210 can transmit DTIM once for every three beacon frames transmitted. STA1 220 and STA2 230 are STAs that operate in PS mode. The STA1 220 and STA2 230 may be configured to switch from sleep to wake at predetermined wakeup intervals to receive TIM elements transmitted by AP 210. Each STA can calculate when to switch to the awake state based on its own local clock, and the example in Figure 9 assumes that the STA clock matches the AP clock.
For example, the predetermined wake-up interval may be set so that the STA1 220 can switch to the awake state at every beacon interval to receive the TIM element. Therefore, the STA1 220 may switch to the awake state when the AP 210 first transmits a beacon frame (S211). The STA1 220 can receive the beacon frame and get the TIM element. When the acquired TIM element indicates that there is a frame to be transmitted to STA1 220, STA1 220 transmits a PS-Poll (Power Save-Poll) frame to AP 210, which requests AP 210 to transmit the frame. Can be done (S221a). AP 210 can transmit frames to STA1 220 in response to PS-Poll frames (S231). After completing the frame reception, the STA1 220 switches to sleep again and operates.
When the AP 210 transmits the second beacon frame, the AP 210 is in a busy medium state, such as another device accessing the medium, so the AP 210 will beacon in time with the correct beacon interval. Frames cannot be transmitted and may be transmitted at the point of delay (S212). In this case, the STA1 220 switches the operation mode to the awake state according to the beacon interval, but cannot receive the delayed beacon frame and switches to the sleep state again (S222).
When AP 210 sends a third beacon frame, the beacon frame can contain a TIM element configured as DTIM. However, because the medium is busy medium, the AP 210 delays the beacon frame and transmits it (S213). The STA1 220 switches to the awake state according to the beacon interval and operates, and can acquire the DTIM from the beacon frame transmitted by the AP 210. It is assumed that the DTIM acquired by STA1 220 indicates that there are no frames transmitted to STA1 220 and there are frames for other STAs. In this case, the STA1 220 can confirm that there are no frames to receive and switch to sleep again to operate. AP 210 transmits the frame to the corresponding STA after transmitting the beacon frame (S232).
AP 210 transmits the fourth beacon frame (S214). However, the STA1 220 could adjust the wake-up interval for receiving the TIM element because it could not get the information that there was buffered traffic for itself from the previous two TIM element receptions. Alternatively, if the beacon frame transmitted by AP 210 contains signaling information for adjusting the wakeup interval value of STA1 220, the wakeup interval value of STA1 220 may be adjusted. In this example, the STA1 220 switches the operating state for receiving the TIM element at every beacon interval, but it may be set to switch the operating state so as to wake up once every three beacon intervals. Therefore, the STA1 220 cannot acquire the TIM element because the AP 210 keeps the sleep state at the time when the AP 210 transmits the 4th beacon frame (S214) and the 5th beacon frame is transmitted (S215).
When AP 210 transmits the sixth beacon frame (S216), STA1 220 switches to the awake state and operates, and can acquire the TIM element contained in the beacon frame (S224). Since the TIM element is a DTIM that indicates that a broadcast frame exists, the STA1 220 can receive the broadcast frame transmitted by the AP 210 without transmitting the PS-Poll frame to the AP 210 ( S234). On the other hand, the wake-up interval set in STA2 230 may be set to a longer cycle than in STA1 220. Therefore, the STA2 230 can switch to the awake state and receive the TIM element at the time when the AP 210 transmits the fifth beacon frame (S215) (S241). The STA2 230 knows from the TIM element that there are frames to be transmitted to itself and can transmit PS-Poll frames to the AP 210 to request frame transmission (S241a). AP 210 is compatible with PS-Poll frames and is STA2 Frames can be transmitted to 230 (S233).
For the operation of the power saving mode as shown in Fig. 9, the TIM element has a TIM that indicates whether or not there is a frame to be transmitted to the STA, or a DTIM that indicates whether or not there is a broadcast / multicast frame. Is included. DTIM can be embodied by setting the fields of the TIM element.
10 to 12 are diagrams for explaining in detail the operation of the STA that has received the TIM.
Referring to FIG. 10, the STA switches from sleep to awake to receive a beacon frame containing TIM from the AP, interprets the received TIM element, and has buffered traffic transmitted to itself. Can be confirmed. The STA may transmit the PS-Poll frame to request the AP to transmit the data frame after contending with other STAs for medium access for the transmission of the PS-Poll frame. .. The AP that receives the PS-Poll frame transmitted by the STA can transmit the frame to the STA. The STA can receive a data frame and transmit an acknowledgment (ACK) frame to it to the AP. After that, the STA can switch to sleep again.
As shown in FIG. 10, the AP operates by an immediate response method in which a PS-Poll frame is received from the STA and then the data frame is transmitted after a predetermined time (for example, SIFS (Short Inter-Frame Space)). can do. On the other hand, if the AP cannot prepare the data frame to be transmitted to the STA during the SIFS time after receiving the PS-Poll frame, it can operate by the deferred response method. This will be described with reference to FIG.
In the example of FIG. 11, the operation of the STA switching from the sleep state to the awake state, receiving the TIM from the AP, and transmitting the PS-Poll frame to the AP via the race condition is the same as the example of FIG. If the AP receives a PS-Poll frame but cannot prepare a data frame during SIFS, it can transmit an ACK frame to the STA instead of transmitting the data frame. When the data frame is prepared after the ACK frame transmission, the AP can transmit the data frame to the STA after competing. The STA may transmit an ACK frame to the AP indicating that the data frame has been successfully received and switch to sleep.
FIG. 12 illustrates an example of an AP transmitting a DTIM. The STA may switch from sleep to awake to receive a beacon frame containing a DTIM element from the AP. It can be seen that these STAs transmit multicast / broadcast frames from the received DTIM. The AP can transmit data (ie, multicast / broadcast frame) immediately after transmission of the beacon frame including DTIM without transmission / reception operation of PS-Poll frame. These STAs may receive data while maintaining the awake state after receiving the beacon frame containing the DTIM, and may switch to the sleep state again after the data reception is completed.
(TIM structure) In the power saving mode operation method based on the TIM (or DTIM) protocol described above with reference to FIGS. 9 to 12, the STA uses the STA identification information contained in the TIM element to transmit a data frame for itself. You can check if it exists. The STA identification information may be information on an AID (Association Identifier), which is an identifier assigned to the STA at the time of association between the STA and the AP.
AID is used as a unique identifier for each STA within a BSS. As an example, in the current wireless LAN system, any one value from 1 to 2007 can be assigned as the AID. In the currently defined wireless LAN system, frames transmitted by AP and / or STA can be assigned 14 bits for AID, and AID values can be assigned up to 16383, but 2008 to 16383 are spares ( reserved) It is set as a value.
The TIM element by existing definition is not suitable for the application of M2M applications where a single AP can have many (eg, more than 2007) STAs associated with it. If the existing TIM structure is extended as it is, the size of the TIM bitmap becomes too large to be supported by the existing frame format, and it is not suitable for M2M communication considering low transmission rate applications. Moreover, in M2M communication, it is expected that the number of STAs in which received data frames exist in one beacon cycle is very small. Therefore, considering the application example of M2M communication as described above, the size of the TIM bitmap becomes large, but it is expected that most of the bits often have a 0 value, so that the bitmap is efficient. The technology to compress is required.
As an existing bitmap compression technique, there is a method of omitting consecutive 0s at the beginning of a bitmap and defining it as an offset (or start point) value. However, although the number of STAs in which buffered frames exist is small, the compression efficiency is not high when the difference in AID value of each STA is large. For example, if only frames transmitted to only two STAs with AIDs of 10 and 2000 are buffered, the length of the compressed bitmap is 1990, but all but both ends are 0. Will have a value. Bitmap compression inefficiencies are less of an issue when the number of STAs that can be associated with an AP is small, but when the number of STAs increases, such inefficiencies hinder overall system performance. It can also be an element to do.
As a measure to solve this, the AID can be divided into a plurality of groups for more effective data transmission. Each group is assigned a specified group ID (GID). Such AIDs assigned on a group basis will be described with reference to FIG.
FIG. 13 (a) is a diagram showing an example of AIDs assigned on a group basis. In the example of FIG. 13 (a), some bits at the beginning of the AID bitmap can be used to indicate the GID. For example, the first two bits in the AID bitmap can be used to indicate four GIDs. When the total length of the AID bitmap is N bits, the values of the first 2 bits (B1 and B2) indicate the GID of the AID.
FIG. 13 (b) is a diagram showing another example of AID assigned on a group basis. In the example of FIG. 13 (b), GID can be assigned according to the position of AID. At this time, AIDs that use the same GID can be expressed by the values of offset and length. For example, when GID 1 is represented by offset A and length B, it means that AIDs A to A + B-1 have GID 1 on the bitmap. For example, in the example of FIG. 13 (b), it is assumed that the AIDs of all 1 to N4 are divided into four groups. In this case, the AIDs belonging to GID 1 are 1 to N1, and the AIDs belonging to this group can be represented by offset 1 and length N1. Next, the AID belonging to GID 2 can be represented by offset N1 + 1 and length N2-N1 + 1, and the AID belonging to GID 3 can be represented by offset N2 + 1 and length N3-N2 + 1. And the AID belonging to GID 4 can be represented by offset N3 + 1 and length N4-N3 + 1.
When such group-based assigned AIDs are introduced, they solve the problem of lack of TIM elements for many STAs by allowing GIDs to allow channel access at different time intervals, while at the same time efficient data. Can be sent and received. For example, in a specific time interval, channel access may be permitted only to STAs corresponding to a specific group, and channel access may be restricted to the remaining other STAs. In this way, a predetermined time period in which access is permitted only to a specific STA can also be called a restricted access window (RAW).
Channel access by GID will be described with reference to FIG. 13 (c). FIG. 13 (c) illustrates the channel access mechanism by beacon interval when the AIDs are divided into three groups. The first beacon interval (or the first RAW) is the interval in which the channel access of the STA corresponding to the AID belonging to GID 1 is permitted, and the channel access of the STA belonging to another GID is not permitted. To achieve this, the first beacon contains a TIM element for AIDs that fall under GID 1. The second beacon frame contains a TIM element only for AIDs with GID 2, which corresponds to AIDs belonging to GID 2 during the second beacon interval (or second RAW). Only STA channel access is allowed. The third beacon frame contains a TIM element for AIDs with GID 3 only, which allows the GID during the third beacon interval (or third RAW). Only channel access of STA corresponding to AID belonging to 3 is allowed. The fourth beacon frame again contains a TIM element for AIDs with GID 1 only, which allows AIDs belonging to GID 1 during the fourth beacon interval (or fourth RAW). Only channel access for the applicable STA is allowed. Subsequently, even if only the channel access of the STA belonging to the specific group indicated by the TIM included in the beacon frame is permitted in each of the 5th and subsequent beacon intervals (or the 5th and subsequent RAW). Good.
FIG. 13 (c) illustrates, but is not limited to, the cyclic or periodic order of GIDs allowed by the beacon interval. That is, by including only AIDs belonging to a specific GID in the TIM element, channel access of only STAs corresponding to these specific AIDs is allowed during a specific time interval (for example, specific RAW), and channel access of the remaining STAs is allowed. Can operate in an unacceptable way.
The group-based AID allocation method described above can also be referred to as the TIM's hierarchical structure. That is, the entire AID space can be divided into a plurality of blocks so that only channel access of the STA corresponding to the specific block having a value other than 0 (that is, the STA of the specific group) is allowed. This divides large sized TIMs into smaller blocks / groups, making it easier for STAs to maintain TIM information and managing blocks / groups depending on STA class, quality of service (QoS), or usage. Although the example of FIG. 13 shows a 2-level hierarchy, a TIM having a hierarchical structure may be configured in the form of two or more levels. For example, 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. In such a case, as an example extension of FIG. 13 (a), in the AID bitmap, the first N1 bits indicate the page ID (ie, PID), and the next N2 bits indicate the block ID. The next N3 bits may be configured in such a way that the sub-block ID is indicated and the remaining bits indicate the STA bit position in the sub-block.
In the examples of the present invention described below, various methods of dividing and managing STAs (or AIDs assigned to each STA) into predetermined hierarchical group units may be applied, and group-based. The AID allocation method is not limited to the above examples.
(U-APSD mechanism) According to the U-APSD (Unscheduled-Automatic Power Save Delivery) mechanism, in order to use the U-APSD service period (SP), the STA may inform the AP of the requested transmission duration. Yes, the AP can transmit frames to the STA during the SP. According to the U-APSD mechanism, the STA can use its own SP to receive a large number of PSDUs from the AP at once.
The STA can recognize from the TIM element of the beacon that there is data that the AP wants to transmit to itself. After that, the STA can request the AP to transmit data while notifying the AP that its own SP has started by transmitting a Trigger frame to the AP at a desired time. The AP can transmit an ACK in response to the trigger frame. The AP can then transmit the RTS to the STA via contention, receive the CTS frame from the STA, and then transmit the data to the STA. Here, the data transmitted by the AP may be composed of one or more data frames. When the AP transmits the last data frame, EOSP (End Of Service) in that data frame If Period) is set to 1 and transmitted to STA, STA can recognize this and terminate SP. This allows the STA to transmit an ACK informing the AP of successful data reception. Thus, according to the U-APSD mechanism, the STA can start its own SP to receive data when it so desires, and can receive multiple data frames within a single SP. , More efficient data reception becomes possible.
(PPDU frame format) Even if the PPDU (Physical Layer Convergence Protocol (PLCP) Packet Data Unit) frame format is configured to include STF (Short Training Field), LTF (Long Training Field), SIG (SIGNAL) field, and Data field. Good. The most basic (eg, non-HT (High Throughput)) PPDU frame format may consist only of L-STF (Legacy-STF), L-LTF (Legacy-LTF), SIG fields and data fields. .. Also, depending on the type of PPDU frame format (eg, HT-mixed format PPDU, HT-greenfield format PPDU, VHT (Very High Throughput) PPDU, etc.), additional (or) between the SIG field and the data field. Other types of 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., and LTF is a signal for channel estimation, frequency error estimation, etc. The STF and LTF can be collectively called the PCLP preamble, and the PLCP preamble can be said to be a signal for synchronization of the OFDM physical layer and channel estimation.
The SIG field can include a RATE field, a LENGTH field, and so on. The RATE field can contain information about the modulation and coding rate of the data. The LENGTH field can contain information about the length of the data. In addition, the SIG field can include a parity bit, a SIG TAIL bit, and so on.
The data field can include a SERVICE field, a PSDU (PLCP Service Data Unit), a PPDU TAIL bit, and optionally a padding bit. Some bits of the SERVICE field can be used for descrambler synchronization at the receiving end. PSDUs correspond to MAC PDUs defined in the MAC layer and can contain data generated / used in the upper layers. The PPDU TAIL bit can be used to return the encoder to the 0 state. Padding bits can be used to fit the length of a data field into a given unit.
MAC PDUs are defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and an FCS (Frame Check Sequence). MAC frames are composed of MAC PDUs and can be transmitted / received through the PSDU of the data portion of the PPDU frame format.
On the other hand, the null-data packet (NDP) frame format means a frame format that does not include data packets. That is, NDP frame means a frame format in which the general PPDU format includes only the PLCP header part (that is, STF, LTF and SIG fields) and does not include the remaining part (that is, data field). NDP frames can also be called short frame formats.
(Slot-based channel access method) FIG. 14 is a diagram for explaining an existing TIM-based channel access method.
In FIG. 14, the STA corresponding to the bit set to 1 in the TIM element included in the beacon frame is found to have data transmitted to itself within the beacon interval, which causes the STA to PS to the AP. -Poll frames or trigger frames can be transmitted. In the example of FIG. 14, it is assumed that a large number of STAs (for example, 2007 or more) are associated with one AP (for example, an outdoor smart grid network). Here, when n bits are set to 1 in the TIM element, n STAs (that is, STA1, STA2, ..., STAn) during a short time interval after the beacon frame is transmitted. Will attempt to transmit a PS-Poll frame or trigger frame to the AP.
In this case, when a large number of STAs are present at the coverage boundary portion of the AP, there may be a problem that the uplink transmissions of the STAs are hidden from each other. In addition, if many bits of the TIM element are set to 1, and the transmission of PS-Poll frames or trigger frames from many STAs occurs during the short time interval after the beacon frame, a hidden node problem. As a result, the problem of transmission collision between STAs increases.
In the present invention, in order to solve such a problem, a slotted channel access method is proposed. Basically, the present invention sets a specific time interval (eg, RAW) that allows a smaller number of STAs to access the uplink channels, or attempts to access the uplink channels of a large number of STAs over a wider time interval. We propose a solution that reduces collisions and improves network performance through a method of distributing between.
FIG. 15 is a diagram for explaining the basic concept of the slot-based channel access method.
The AP can deliver information for the AID segment to the STA through a DTIM notification and subsequent TIM notifications. The entire TIM bitmap can be divided into one or more segment blocks, and the combination of one or more TIM elements can form the entire TIM bitmap. That is, the segment block can be part of the entire TIM bitmap. The AID segment information contained in the DTIM notification or the TIM notification can include, for example, information regarding the segment block offset and the segment block range, the TIM for the AID segment, the duration of the RAW, and the like. The segment block offset is the starting position of the AID segment and the segment block range can mean its length. This allows only the STA covered by the AID segment (ie, the STA with the AID contained in the AID segment) to access the channel within the DTIM or RAW immediately after the TIM notification.
Also, one RAW can be divided into one or more time slots. The slot duration can be set differently for each RAW. However, when one RAW includes a plurality of slots, the duration of the plurality of slots may be set to the same value. Information about slot duration for each RAW may be included in the beacon frame, and the STA in dose mode wakes up to TBTT (Target Beacon Transmission Time) and listens to the beacon frame in RAW. Slot duration information can be acquired.
In this way, the STA corresponding to the AID segment provided through DTIM or TIM notification is found to be an STA that allows channel access in RAW immediately after DTIM or TIM, and from the slot duration information, it is found in the RAW. You can see the slot duration. Further, if the STA can also know the information on the RAW duration, it is possible to infer or determine how many slots the RAW includes from the slot duration information and the RAW duration information.
Here, the STA can determine the position of the slot in the RAW that it must (or allows) channel access based on its AID bit position. The STA can obtain its AID bit position from a specific information element (IE). In the present invention, such IE is called RPS (RAW Parameter Set) IE in the sense that it is a set of parameters required for media access that is restrictedly permitted only for a group of STAs, or a grouping parameter set. It is called (GrPS IE).
FIG. 16 is a diagram illustrating an exemplary format of RPS IE.
The element ID field can be set to a value that indicates that the IE is an RPS IE.
The Length field can be set to a value that indicates the length of the field after the Length field. Depending on the value of the length field, the number of subsequent RAW fields (or RAW assignment fields) can be determined.
RPS IE may contain N RAW fields (or RAW assigned fields), one RAW field containing parameters for one RAW.
The subfield included in one RAW field shown in FIG. 16 will be specifically described with reference to FIG. 17 additionally.
FIG. 17 is a diagram for explaining a configuration of RAW according to an example of the present invention.
The Group ID field of FIG. 16 includes a segment bitmap or a block bitmap, and provides identification information of a group whose access is restricted within the RAW section. That is, the group ID field can contain information that identifies the AID segment block, such as the start index, block length, or end index of the AID segment block. In this sense, the group ID field can also be called a RAW group field.
The RAW Start Time field of FIG. 16 can contain information about the start time when media access is allowed for the STA group. The RAW start time point can be expressed by the difference value (or the duration value between them) between the time point when the beacon transmission ends and the time point when the RAW starts, and the unit may be TU (Time Unit). The TU may be configured in units of microseconds (μs) and can be defined as, for example, 1024 μs. If the RAW start time is set to a 0 value, RAW may start immediately after the end of the beacon frame, as in the example of FIG.
The RAW Duration field of FIG. 16 can contain information about the length of time (ie, duration) that the STA group is allowed to access media. The RAW duration corresponds to the difference between the RAW start time and the RAW end time, and the unit may be TU.
The RAW Slot Duration field of FIG. 16 can contain information about the length of time (ie, duration) of each channel access slot contained in a single RAW. As described above, one RAW may be composed of one slot, one RAW may be composed of a plurality of time slots, and in this case, the duration of a plurality of slots included in one RAW. Have the same value. FIG. 17 shows a case where 6 slots are defined in one RAW duration, and the durations of the 6 slots are set to the same value.
The RAW Slot Boundary field in Figure 16 indicates that Transmission Opportunity (TXOP) or transmission within TXOP extends across (or crosses) the slot boundary. It can be set to a value indicating whether or not it is allowed. The slot boundary, as shown in FIG. 17, means a time point that serves as a reference for dividing consecutive slots. In this sense, the RAW Slot Boundary field can also be referred to as the cross slot boundary field.
If TXOP (or transmission within TXOP) is not allowed to cross the slot boundary, TXOP (or transmission within TXOP) must terminate before the slot boundary. For example, in the example of FIG. 17, a STA transmitting an attempt to access a channel in the first slot (ie, an uplink frame (PS-Poll or trigger frame)) receives data from the AP through the downlink frame, which. An ACK frame can be transmitted to the AP in response to, but if TXOP (or transmission within the TXOP) is not allowed to cross the slot boundary, the transmission of such an ACK frame is performed within the slot. Must be completed. The AP can also inform each RAW whether the TXOP rules described above (ie, TXOP (or transmission within TXOP) are not allowed to cross slot boundaries) apply. When such a TXOP rule is applied, the STA does not have to wait for the probe delay when waking up at the slot boundary.
The RAW Slot AID field in Fig. 16 should be set to a value that indicates whether channel access is permitted only for STAs in which the bit corresponding to the AID of the STA is set to 1 in the TIM element. Can be done. That is, channel access (ie, uplink frame transmission) of only the STA corresponding to the AID whose bit value is set to 1 (that is, paged) in the TIM bitmap is allowed, or the TIM bit. Whether channel access (ie, uplink frame transmission) is allowed regardless of whether the bit value is set to 1 in the map (ie, all STAs that are paging or not paging). It may be indicated by the RAW slot AID field. In this sense, the RAW slot AID field can also be referred to as an Access Restricted to Paged STAs Only field.
The fields included in GrPS IE or RPS IE in FIG. 16 are merely examples, and the fields containing substantially the same information as the above-mentioned fields are also included in the scope of the present invention when they are composed of other forms. .. Further, the format of GrPS IE or RPS IE proposed in the present invention is not limited to the field of FIG. 16, and includes a part of the fields of FIG. 16 or is not shown in FIG. Also includes a form that further includes the field of.
Further, the GrPS IE or RPS IE described with reference to FIG. 16 can be transmitted through a beacon frame, a probe response frame, and the like. When transmitted through a beacon frame, it can also be described as broadcasting GrPS IE or RPS IE by the AP, and when transmitted through a probe response frame, the AP unicasts GrPS IE or RPS IE. It can also be expressed as a thing.
(Slot assignment) The STA can operate in a doze (or slip) state prior to the channel access slot assigned to it. The STA can wake up at the slot boundaries of its assigned channel access slots and initiate channel access in an EDCA manner (ie, in a competing manner).
Here, which STA is assigned to which slot can be determined by the following method.
The channel access slot of each STA can be basically determined by the modulo operation of the AID of the STA and the total number of slots of the RAW. For example, STA is the index of slots (i) that are allowed to initiate access to the channel.<sub>slot</sub>) Can be determined based on the following formula.
<maths num="1"><img id="000004" he="21" wi="71" file="JP5961749B2_D0001.tif" img-format="tif" img-content="drawing" /></maths> In the above formula 1, f (AID) is a value determined based on the AID of the STA. For example, f (AID) may be defined by using the value of AID itself or using some bits of AID.
In formula 1 above, N<sub>RAW</sub>Is the total number of slots in the RAW, N<sub>RAW</sub>= T<sub>RAW</sub>/ T<sub>slot</sub>Can be calculated by. Where T<sub>RAW</sub>Is the RAW duration value, T<sub>slot</sub>Is the slot duration value.
In Equation 1 above, mod means modulo operation, and A mod B means the remaining value of A divided by B. A mod B can also be expressed as A% B.
In the example of the above formula 1, the total AID (full AID) of STA may be used for f (AID). Alternatively, a partial AID (Partial AID) may be used for f (AID) instead of the AID. Partial AID is a non-unique identifier of STA and can be determined by a hashing function that utilizes some bits of the entire AID.
When a Partial AID is used in the slot allocation calculation, multiple STAs (eg, STAs with consecutive AID values) may be assigned to use the same channel access slot. For example, in Equation 1 above, f (AID) can be defined as being determined based on AID [a: b]. Here, AID [a: b] means from Bit [a] to Bit [b] of the binary number AID. The value of a or b may be provided by the AP to each slot.
For example, it can be assumed that the slot allocation is determined using AID [3:12]. AID [3:12] means Bit3 to Bit12 out of the total 14-bit (that is, Bit0 to Bit13) AID. In this case, regardless of the values of Bit0, Bit1, Bit2, and Bit13 of AID, all STAs with the same value of Bit3 to Bit12 of AID may operate as if channel access in the slot is allowed. it can.
Alternatively, in an example as shown in FIG. 20 described later, RAW is restrictedly assigned to a STA having an AID corresponding to a bit having a bit value of 1 (that is, a paged STA) on the bitmap of the TIM element. In the case, f (AID) in the above formula 1 is the position index (position) of the AID bit in the TIM element. It may be determined based on the index) value. That is, in the example shown in FIG. 20, when a total of four bits (that is, the first, third, sixth, and ninth bits) of the TIM bitmap are set to 1, the first bit. The position index of AID1 corresponding to is 1 and the position index of AID3 corresponding to the 3rd bit is 2 and the position index of AID6 corresponding to the 6th bit is 3 and corresponds to the 9th bit. It can be determined that the position index of AID9 is 4. That is, when the AIDs having a bit value of 1 are arranged in the order of increasing in the TIM element, the order value can correspond to the position index. This assigns the STA with AID1 to the first slot in RAW, the STA with AID3 to the second slot in RAW, and the STA with AID6 to the third slot in RAW. , STA with AID9 is assigned the 4th slot in RAW.
In comparison, as described above, when the f (AID) value is defined to utilize the AID (or Partial AID) of STA, the bit value is 1 on the bitmap of the TIM element. It may be defined as being used when RAW is not restrictedly allocated only to STAs with AIDs corresponding to (eg, paged STAs). That is, if any (any) STA (eg, all STAs, whether paging or not) is allowed channel access in RAW, then within that RAW based on that STA's AID. It may be determined which slot is assigned to the STA.
Information about slot allocation as described above may be additionally included (eg, in the form of a field called slot assignment) in the GrPS or RPS IE of FIG.
(Example behavior of slot-based channel access) FIG. 18 is a diagram for explaining an example of slot-based channel access according to the present invention.
In the example of FIG. 18, it is assumed that GrPS or RPS IE for RAW1 indicates that only STAs that meet the following conditions are allowed channel access on RAW1.
-RAW Slot AID field: The bit value limit of the TIM element corresponding to the STA's AID is applied (ie, the STA's AID bit value is set to 1 (ie, paging) in the TIM element. Only channel access is allowed). FIG. 18 illustrates an example in which only STAs having AIDs corresponding to the 1st, 3rd, 6th, and 9th bits in the TIM bitmap are allowed to access the channel with RAW1.
-RAW Slot Duration field: T<sub>s1</sub>Set to (where T<sub>s1</sub>= PS-Poll frame length + SIFS + ACK frame length, or T<sub>s1</sub>= Null Data Trigger frame length + SIFS + ACK frame length).
-RAW Slot Boundary field: Indicates that TXOP (or transmission within TXOP) is not allowed to cross slot boundaries.
When set as above, RAW1 in Figure 18 can only be used for PS-Poll or Null-Data trigger frames.
On the other hand, in the example of FIG. 18, it is assumed that GrPS or RPS IE for RAW2 indicates that channel access is allowed on RAW2 only for STAs that satisfy the following conditions.
-RAW Slot AID field: The bit value limit of the TIM element corresponding to the STA's AID is applied (ie, the STA's AID bit value is set to 1 (ie, paging) in the TIM element. Only channel access is allowed). FIG. 18 illustrates the case where only STAs with AIDs corresponding to the 1st, 3rd, 6th, and 9th bits in the TIM bitmap are allowed to access the channel on RAW2.
-RAW Slot Duration field: T<sub>s2</sub>Set to (where T<sub>s2</sub> Data frame length + SIFS + ACK frame length).
-RAW Slot Boundary field: Indicates that TXOP (or transmission within TXOP) is not allowed to cross slot boundaries.
When set as above, RAW2 in FIG. 18 can be used by the AP to transmit a data frame to a STA with an AID that corresponds to a bit with a bit value of 1 in the TIM bitmap.
FIG. 19 is a diagram for explaining another example of slot-based channel access according to the present invention.
In the example of FIG. 19, it is assumed that GrPS or RPS IE for RAW1 indicates that only STAs that meet the following conditions are allowed channel access on RAW1.
-RAW Slot AID field: No bit-value restrictions apply for the TIM element that corresponds to the STA's AID (ie, regardless of whether the STA's AID bit value is set to 1 in the TIM element (ie, paging). (Whether or not it is done), RAW1 allows channel access for all STAs). In FIG. 19, RAW1 allows channel access of STAs having AIDs corresponding to the 1st, 3rd, 6th, and 9th bits in the TIM bitmap, as well as other STAs that do not.
-RAW Slot Duration field: T<sub>s1</sub>Set to (where T<sub>s1</sub>= PS-Poll frame length + SIFS + ACK frame length, or T<sub>s1</sub>= Null Data Trigger frame length + SIFS + ACK frame length).
-RAW Slot Boundary field: Indicates that TXOP (or transmission within TXOP) is not allowed to cross slot boundaries.
When set as above, RAW1 in Figure 19 can be used for any STA PS-Poll, Null-Data trigger frame or any small control frame. ..
On the other hand, in the example of FIG. 19, it is assumed that GrPS or RPS IE for RAW2 indicates that channel access is allowed on RAW2 only for STAs that satisfy the following conditions.
-RAW Slot AID field: No bit-value restrictions apply for the TIM element that corresponds to the STA's AID (ie, regardless of whether the STA's AID bit value is set to 1 in the TIM element (ie, paging). (Whether or not it is done), RAW2 allows channel access for all STAs). In Figure 19, RAW2 allows channel access for STAs that have AIDs that correspond to the 1st, 3rd, 6th, and 9th bits in the TIM bitmap, as well as other STAs that do not.
-RAW Slot Duration field: T<sub>s2</sub>Set to (where T<sub>s2</sub> Data frame length + SIFS + ACK frame length).
-RAW Slot Boundary field: Indicates that TXOP (or transmission within TXOP) is not allowed to cross slot boundaries.
When set as above, RAW2 in FIG. 19 can be used by an AP or any STA to transmit a data frame to any STA or AP, respectively.
(Multicast / Broadcast transmission slot) When dividing a RAW into one or more time slots, the first one or more slots or the last one or more slots in one RAW may be assigned for multicast or broadcast use. The STA must always remain awake between slots assigned for multicast / broadcast use in RAW.
To that end, GrPS or RPS IE, which defines parameters for RAW and channel access slots, may further include a RAW Multicast / Broadcast Slot Duration field.
The RAW Multicast / Broadcast Slot Duration field can be used to inform the STA group of information about the duration for allowed multicast / broadcast medium access.
FIG. 20 is a diagram for explaining multicast / broadcast slot allocation in RAW according to an example of the present invention.
In the example of FIG. 20, the first slot of RAW2 is assigned for multicast / broadcast use, and the AP can transmit the multicast / broadcast frame in the first slot. All STAs are awake in the first slot.
Multicast / broadcast slots may also be used to re-configure RAW slot allocations.
For example, in the example of FIG. 20, channel access is permitted only to a specific STA (for example, a paged STA) in RAW1 and RAW2 through the TIM element and GrPS element (or RPS element) of the beacon frame. The slot that is set and assigned to the specific STA may be determined. For example, as mentioned above, the STA with AID1 is in the first slot, the STA with AID3 is in the second slot, the STA with AID6 is in the third slot, and the STA with AID9 is in the fourth slot. Can be assigned.
A RAW1 paged STA (ie, an STA with the AID bit set to 1 in the TIM bitmap of the beacon frame) is a downlink frame buffered in the AP by transmitting a PS-Poll frame or trigger frame. Can be requested from the AP to transmit.
Here, as shown in FIG. 20, the STA with AID6 was assigned the third slot of RAW1, but could not change from the doze state to the awake state at the slot boundary where the third slot started, and the third slot. Suppose the PS-Poll frame or trigger frame could not be transmitted in the slot of.
From the AP's point of view, I also assigned a slot (for example, the third slot) in RAW2 to transmit a downlink frame to the STA with AID6, but PS-Poll / trigger from the STA with AID6 in RAW1. Since the frame could not be received, if the slot allocation to the STA with AID6 is left as it is, it can be expected that the STA cannot transmit the PS-Poll / trigger frame in the slot even in RAW2. Therefore, the AP needs to retrieve the slots allocated for the STA with AID6.
Therefore, the AP can transmit the RAW announcement frame in the first slot of RAW2 assigned as the multicast / broadcast slot. RAW notification frames include GrPS IE (or RPS IE). That is, the AP sets the next RAW (ie, RAW2) for the RAW (eg, RAW Duration, RAW Slot Duration, slot) based on whether RAW1 receives a PS-Poll / trigger frame from the STA. Assignment etc.) can be newly performed. That is, even if it is not a beacon frame, information related to resource allocation in RAW can be transmitted at the beginning of the RAW (at the beginning of the RAW).
In such a case, the slot allocation to the STA is determined based on the remaining slots that can be allocated (that is, the total slots included in the RAW) excluding the multicast / broadcast slot. For example, in the example of FIG. 20, the first slot of RAW2 is excluded from the slot allocation to the STA, and the remaining three slots (that is, the second, third, and fourth slots) are slotted to the STA. May be determined. The slot allocation information may be included in a RAW notification frame (that is, a frame containing information regarding resource allocation in the RAW) at the start of the RAW, and the slot allocation method may be determined in the same manner as the above-described method. ..
FIG. 21 is a diagram for explaining multicast / broadcast slot allocation in RAW according to another example of the present invention.
In the example of FIG. 20 above, it is assumed that the multicast / broadcast slot is always located at the start of RAW, but in the example of FIG. 21, the multicast / broadcast slot is not only in the first slot of RAW but also in other slots. Shows a method that can also be positioned. In the example of FIG. 21, the case where the multicast / broadcast slot is located at the end in RAW is shown. In this case, when defining the RAW Multicast / Broadcast Slot Duration field in GrPS IE (or RPS IE), the information that indicates the location of the Multicast / Broadcast slot (ie, RAW Multicast / Broadcast Slot Offset). ) May be included.
For example, if the Nth slot in RAW1 is assigned as a multicast / broadcast slot, the value of the RAW multicast / broadcast slot offset field can be set to N. If the multicast / broadcast slot is first located in RAW, the value of the RAW multicast / broadcast slot offset field is set to 0, and if the multicast / broadcast slot is last located in RAW, then in the RAW multicast / broadcast offset field. The value may be set to 255.
FIG. 22 is a diagram for explaining a channel access method according to an example of the present invention.
In step S2210, the first STA (eg, AP) to the second STA (eg, non-AP STA) can receive RAW information. The RAW information may be the GrPS element or RPS element described above, or may be transmitted through a beacon frame.
In step S2220, the second STA, based on the RAW information, determines whether or not it belongs to a group that allows channel access in RAW, and the temporal position and length of RAW that allows channel access. (That is, the RAW start time and duration) can be determined, and which slot in the RAW is allowed to access its own channel, the length of the slot, and the like can be determined. In addition, the channel access method is determined by whether or not transmission beyond the slot boundary is permitted when acquiring TXOP in RAW and performing transmission, and whether or not channel access of only the paged STA is permitted. can do.
At step S2230, the second STA can attempt channel access. That is, the second STA can access the channel based on EDCA (ie, in a competitive manner).
In the channel access method described with reference to FIG. 22, the matters described in the various embodiments of the present invention described above are applied independently, or two or more embodiments are applied simultaneously. You may.
FIG. 23 is a block diagram showing a configuration of a wireless device according to an embodiment of the present invention.
The AP10 can include a processor 11, a memory 12, and a transmitter / receiver 13. The STA20 can include a processor 21, a memory 22, and a transmitter / receiver 23. The transmitters and receivers 13 and 23 can transmit / receive radio signals and, for example, can embody a physical layer based on an IEEE 802 system. Processors 11 and 21 can be connected to transmitters and receivers 13 and 21 to embody a physical layer and / or a MAC layer based on an IEEE 802 system. Processors 11 and 21 may be configured to perform the operations according to the various embodiments of the present invention described above. Further, modules embodying the operations of the AP and STA according to the various embodiments of the present invention described above may be stored in the memories 12 and 22 and executed by the processors 11 and 21. The memories 12 and 22 may be contained inside the processors 11 and 21, or may be provided outside the processors 11 and 21 and connected to the processors 11 and 21 by known means.
The specific configuration of such an AP and STA apparatus is embodied so that the matters described in the various embodiments of the present invention described above may be applied independently, or two or more embodiments may be applied simultaneously. The duplicated content may be omitted for clarity.
The above-described embodiment of the present invention can be embodied by using various means. For example, the embodiments of the present invention can be embodied by hardware, firmware, software, or a combination thereof.
In the case of hardware implementation, the method according to the embodiment of the present invention is one or more ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), DSPDs (Digital Signal Processing Devices), PLDs (Programmable Logic). It can be realized by Devices), FPGAs (Field Programmable Gate Arrays), processors, controllers, microcontrollers, microprocessors, etc.
In the case of realization by firmware or software, the method according to the embodiment of the present invention can be embodied in the form of a module, procedure or function that executes the function or operation described above. The software code may be stored in a memory unit and driven by a processor. The memory unit is provided inside or outside the processor and can exchange data with the processor by various already known means.
A detailed description of preferred embodiments of the invention disclosed as described above has been provided so that those skilled in the art can embody and practice the invention. Although the above description has been made with reference to preferred embodiments of the present invention, skilled skill in the art will be able to do so within the scope of the ideas and areas of the invention described in the claims below. , It can be understood that the present invention can be modified and modified in various ways. Therefore, the present invention is not limited to the embodiments disclosed herein, but is intended to provide the broadest scope consistent with the principles and novel features disclosed herein.
Although the various embodiments of the present invention described above have been described focusing on the IEEE 802.11 system, they may be applied to various mobile communication systems in the same manner.
28 sheets
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Every citation, both ways
| Document | Relation | Office |
|---|---|---|
| JP2010519875A | Cites | Japan |
| JP2015502111A | Cites | Japan |
| Nokia,"Group Synchronized DCF",IEEE 802.11-12/0329r1,2012年 3月12日 | Non-patent | – |
| I2R,"Supporting Low Power Operation",IEEE 802.11-12/0409r2,2012年 3月13日 | Non-patent | – |
| LG Electronics,"Uplink Channel Access General Procedure",IEEE 802.11-12/0831r0,2012年 7月12日 | Non-patent | – |
56 members in 11 offices
Priority claims19
| Document | Office | Kind | Date |
|---|---|---|---|
| 201261639877 | United States of America | P | |
| 201261639877 | United States of America | P | |
| 61639877 | United States of America | – | |
| 201261651002 | United States of America | P | |
| 201261651002 | United States of America | P | |
| 61651002 | United States of America | – | |
| 201261680227 | United States of America | P | |
| 201261680227 | United States of America | P | |
| 61680227 | United States of America | – | |
| 2013003660 | Republic of Korea | W | |
| 2013003660 | Republic of Korea | W | |
| 61639877 | – | – | – |
| 61651002 | – | – | – |
| 61680227 | – | – | – |
| KR2013003660 | – | – | – |
| US201261639877P | – | – | – |
| US201261651002P | – | – | – |
| US201261680227P | – | – | – |
| WO2013KR03660 | – | – | – |
Members56
| Document | Office | Kind | |
|---|---|---|---|
| CA2871482A1 | Canada | A1 | |
| WO2013162338A1 | World Intellectual Property Organization (WIPO) | A1 | |
| WO2013162339A1 | World Intellectual Property Organization (WIPO) | A1 | |
| WO2013162340A1 | World Intellectual Property Organization (WIPO) | A1 | |
| AU2013253132A1 | Australia | A1 | |
| KR20150000487A | Republic of Korea | A | |
| KR20150000488A | Republic of Korea | A | |
| KR20150000489A | Republic of Korea | A | |
| CN104272845A | China | A | |
| CN104272847A | China | A | |
| CN104303580A | China | A | |
| MX2014012920A | Mexico | A | |
| EP2844014A1 | European Patent Office (EPO) | A1 | |
| EP2844015A1 | European Patent Office (EPO) | A1 | |
| EP2844017A1 | European Patent Office (EPO) | A1 | |
| US2015071211A1 | United States of America | A1 | |
| AU2013253132B2 | Australia | B2 | |
| US2015124722A1 | United States of America | A1 | |
| US2015131547A1 | United States of America | A1 | |
| EP2844015A4 | European Patent Office (EPO) | A4 | |
| JP2015519788A | Japan | A | |
| JP2015519796A | Japan | A | |
| JP2015519797A | Japan | A | |
| KR101579468B1 | Republic of Korea | B1 | |
| KR101579469B1 | Republic of Korea | B1 | |
| EP2844017A4 | European Patent Office (EPO) | A4 | |
| EP2844014A4 | European Patent Office (EPO) | A4 | |
| MX338026B | Mexico | B | |
| RU2586590C1 | Russian Federation | C1 | |
| JP5961748B2 | Japan | B2 | |
| JP5961749B2This record | Japan | B2 | |
| KR101651138B1 | Republic of Korea | B1 | |
| JP5982057B2 | Japan | B2 | |
| US9451636B2 | United States of America | B2 | |
| US2016345358A1 | United States of America | A1 | |
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| JP2016201809A | Japan | A | |
| JP2016201810A | Japan | A | |
| US2017019920A1 | United States of America | A1 | |
| US9578655B2 | United States of America | B2 | |
| US2017127419A1 | United States of America | A1 | |
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| JP6181819B2 | Japan | B2 | |
| EP2844015B1 | European Patent Office (EPO) | B1 | |
| US9756660B2 | United States of America | B2 | |
| US9781722B2 | United States of America | B2 | |
| EP3232725A1 | European Patent Office (EPO) | A1 | |
| JP6215400B2 | Japan | B2 | |
| US9801208B2 | United States of America | B2 | |
| EP2844017B1 | European Patent Office (EPO) | B1 | |
| CN104272845B | China | B | |
| CN104303580B | China | B | |
| EP2844014B1 | European Patent Office (EPO) | B1 | |
| CN104272847B | China | B | |
| CA2871482C | Canada | C | |
| EP3232725B1 | European Patent Office (EPO) | B1 |
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Numbers
- Publication
- 5961749
- Publication, DOCDB
- 5961749
- Publication, EPODOC
- JP5961749B
- Application
- 2015506913
- Application, DOCDB
- 2015506913
- Application, EPODOC
- JP20150506913
Titles2
- Japanese
- 無線LANシステムにおけるチャネルアクセス方法及び装置
- English
- Channel access methods and devices in wireless LAN systems
Classification
- CPC, 12
- H04W52/0216
- H04W74/04
- H04W74/006
- H04W84/12
- Y02D30/70
- H04W4/08
- H04W52/02
- H04W74/08
- H04W72/30
- H04W40/244
- H04W72/0446
- H04W72/0453
- IPC, 5
- H04W74 04
- H04J3 16
- H04W48 10
- H04W72 04
- H04W84 12
