Preamble selection for simultaneous transmissions in a wireless local area network (WLAN) system

Abstract

There is a desire to add flexibility in providing wireless point-to-multipoint services.SOLUTION: Systems, methods, and instrumentalities are provided for determining a physical layer (PHY) protocol data unit (PPDU) format. A determination may be made as to whether a basic service set (BSS) includes a first type of legacy station, wherein the first type of legacy station is a pre- 802. 11n station. A determination may be made as to whether the stations in the BSS support short format preambles. A determination may be made as to whether beamforming or precoding will be used in connection with an upcoming multi-user transmission.SELECTED DRAWING: Figure 22

Description

[Background technology]

[0001] The present invention relates to a system, method and means for determining a physical layer (PHY) protocol data unit (PPDU) format.

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 049,978, filed September 12, 2014, the disclosure of which is incorporated herein by reference in its entirety.

[0003] A wireless network (e.g., an IEEE 802.11ac-based network) may provide an access point (AP) to one or more stations (STAs) in a basic service set (BSS) having one or more operating channels. The AP may have access to or interface with a distribution system (DS) or another type of wired / wireless network that carries traffic into and out of the BSS. Traffic originating at a STA outside the BSS arrives through the AP and can be delivered to the STA. Traffic originating at a STA for destinations outside the BSS can be sent to the AP and then delivered to the respective destination. Summary of the Invention [Problem to be solved by the invention]

[0004] Traffic between STAs within a BSS can be transmitted through an AP, where a source STA transmits traffic to an AP, and the AP delivers the traffic to a destination STA. Such traffic between STAs within a BSS can be peer-to-peer traffic. Such peer-to-peer traffic can be transmitted directly between the source and destination STAs using Direct Link Setup (DLS), for example, using 802.11e DLS or 802.11z Tunneled DLS (TDLS). A WLAN in independent BSS mode may not have an AP, and STAs communicate directly with each other. Therefore, adding flexibility in providing wireless point-to-multipoint services is desirable. [Means for solving the problem]

[0005] A system, method, and means are provided for determining a physical layer (PHY) protocol data unit (PPDU) format. A determination can be made as to whether a basic service set (BSS) includes a first type of legacy station, the first type being a pre-802.11n device. A determination can be made as to whether stations in the BSS support short-format preambles. A determination can be made as to whether beamforming or precoding will be used in connection with an upcoming multi-user transmission. An indication of a selected PPDU preamble format can be transmitted to stations in the BSS via a multi-user transmission, where when the BSS includes the first type of legacy station, a long-format preamble is selected and beamforming is used in connection with the upcoming multi-user transmission, or precoding is used in connection with the upcoming multi-user transmission. When the BSS does not include the first type of legacy station, a short-format preamble is selected, beamforming is not used in connection with the upcoming multi-user transmission, and precoding is not used in connection with the upcoming multi-user transmission. [Effects of the Invention]

[0006] Adds flexibility to wireless point-to-multipoint services. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 1 illustrates an exemplary communication system. [Figure 1B] FIG. 1 illustrates an exemplary wireless transmit / receive unit (WTRU). [Figure 1C] FIG. 1 illustrates an exemplary wireless local area network (WLAN). [Figure 2] 1A and 1B are diagrams illustrating examples of three physical layer (PHY) protocol data unit (PPDU) formats in 802.11n (high throughput). [Figure 3] FIG. 10 is a diagram illustrating an example of an S1G short format. [Figure 4] FIG. 10 is a diagram of an example SIG field using the S1G short format. [Figure 5] FIG. 10 is a diagram illustrating an example of an S1G long format. [Figure 6] A figure showing an example of a SIG-A field in the S1G long format when single-user transmission is used. [Figure 7] A figure showing an example of a SIG-A field in the S1G long format when multi-user transmission is used. [Figure 8] FIG. 10 is a diagram illustrating an example of the S1G 1M format. [Figure 9] A diagram showing an example of the SIG field in the S1G 1M format. [Figure 10] FIG. 10 is a diagram illustrating an example of a VHT mixed format packet of 802.11ac. [Figure 11] FIG. 10 illustrates an example of a membership status array field. [Figure 12] FIG. 10 illustrates an example of a user position array field. [Figure 13] A diagram showing an example of HEW PPDU design for simultaneous transmission. [Figure 14] FIG. 10 illustrates an example of a HEW PPDU for UL MU-MIMO. [Figure 15] FIG. 10 illustrates an example of a HEW PPDU for UL MU-MIMO. [Figure 16] FIG. 10 is a diagram illustrating an example of hewSTF / hewLTF for UL MU-MIMO. [Figure 17] FIG. 10 illustrates another example of hewSTF / hewLTF for UL MU-MIMO. [Figure 18] FIG. 10 is a diagram of an example of hewSTF / hewLTF for UL MU-MIMO. [Figure 19] FIG. 10 is a diagram of an example of hewSTF / hewLTF for UL MU-MIMO. [Figure 20] 1 illustrates an example PPDU design (e.g., long OFDMA PPDU) for coordinated orthogonal block-based resource allocation, such as orthogonal frequency division multiple access (OFDMA) transmission using subchannel sizes of 20 MHz or greater. [Figure 21] 1 illustrates an example PPDU design for OFDMA transmission using subchannel sizes of 20 MHz or greater (eg, short OFDMA PPDU). [Figure 22] FIG. 10 illustrates an example of a procedure for selecting a long / short OFDMA PPDU format. [Figure 23] 1 illustrates an example PPDU design for OFDMA transmission using subchannel sizes of 20 MHz or greater (eg, long OFDMA PPDU). [Figure 24] 1 illustrates an example PPDU design for OFDMA transmission using subchannel sizes of 20 MHz or greater (eg, short OFDMA PPDU). [Figure 25] 1 illustrates an example PPDU design for OFDMA transmission using subchannel sizes of 20 MHz or greater (eg, short OFDMA PPDU). [Figure 26]FIG. 10 illustrates an example of a transmission design for the hewSIG field. [Figure 27] FIG. 1 is a diagram of an example of an uplink multi-user channel access scheme. DETAILED DESCRIPTION OF THE INVENTION

[0008] A detailed description of illustrative embodiments will now be provided with reference to various figures. While this description provides detailed examples of possible implementations, it should be noted that the details are intended to be illustrative and are in no way intended to limit the scope of the present application. Additionally, while the figures may show one or more message charts, they are intended to be illustrative (messages may be changed, rearranged, or even omitted where appropriate).

[0009] 1A is a diagram of an example communication system 100 capable of implementing one or more disclosed features. For example, a wireless network (e.g., a wireless network comprising one or more components of communication system 100) can be configured to assign QoS characteristics to bearers that extend beyond the wireless network (e.g., beyond a walled garden associated with the wireless network).

[0010] The communications system 100 may be a multiple-access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable the multiple wireless users to access such content through sharing of system resources, including wireless bandwidth. For example, the communications system 100 may utilize one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), and single-carrier FDMA (SC-FDMA).

[0011] 1A, the communications system 100 may include at least one wireless transmit / receive unit (WTRU), e.g., multiple WTRUs, such as WTRUs 102a, 102b, 102c, and 102d, a radio access network (RAN) 104, a core network 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, and 102d may be any type of device configured to operate and / or communicate in a wireless environment. As examples, the WTRUs 102a, 102b, 102c, 102d may be configured to transmit and / or receive wireless signals and may include user equipment (UE), mobile stations, fixed or mobile subscriber units, pagers, cellular phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, and home appliances.

[0012] The communications system 100 may also include a base station 114a and a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications networks, such as the core network 106, the Internet 110, and / or the network 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNodeB, a Home Node B, a Home eNodeB, a site controller, an access point (AP), a wireless router, etc. Although the base stations 114a, 114b are each shown as a single element, it should be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0013] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals within a particular geographic area, sometimes referred to as a cell (not shown). A cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In another embodiment, the base station 114a may utilize multiple-input multiple-output (MIMO) technology and, therefore, may utilize multiple transceivers for each sector of the cell.

[0014] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over the air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0015] More specifically, as mentioned above, the communication system 100 may be a multiple-access system and may utilize one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA. For example, the base station 114a and the WTRUs 102a, 102b, and 102c in the RAN 104 may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using Wideband CDMA (WCDMA). WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink Packet Access (HSDPA) and / or High Speed ​​Uplink Packet Access (HSUPA).

[0016] In another embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE Advanced (LTE-A).

[0017] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE), and GSM EDGE (GERAN).

[0018] The base station 114b in FIG. 1A may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a workplace, home, vehicle, campus, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Therefore, the base station 114 b may not need to access the Internet 110 via the core network 106 .

[0019] The RAN 104 can communicate with the core network 106, which can be any type of network configured to provide voice, data, application, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, and 102d. For example, the core network 106 can provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A , it should be understood that the RAN 104 and / or core network 106 can communicate directly or indirectly with other RANs that utilize the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which can utilize E-UTRA radio technology, the core network 106 can also communicate with another RAN (not shown) that utilizes GSM radio technology.

[0020] The core network 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network providing plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Internet Protocol (IP) in the TCP / IP Internet protocol suite. The network 112 may include wired or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another core network connected to one or more RANs, which may utilize the same RAT as the RAN 104 or a different RAT.

[0021] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities, i.e., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links. For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a that may utilize cellular-based wireless technology and with a base station 114b that may utilize IEEE 802 wireless technology.

[0022] 1B illustrates an exemplary wireless transmit / receive unit, WTRU 102. WTRU 102 may be used in one or more of the communication systems described herein. As shown in FIG. 1B, WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and other peripherals 138. It should be understood that WTRU 102 may include any subcombination of the above elements while remaining consistent with an embodiment.

[0023] The processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors in conjunction with a DSP core, a controller, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other function that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it should be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0024] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In another embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive, for example, IR signals, UV signals, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and receive both RF signals and light signals. It should be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0025] 1B, the transmit / receive element 122 is shown as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may utilize MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0026] The transceiver 120 may be configured to modulate signals transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as, for example, UTRA and IEEE 802.11.

[0027] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. Additionally, the processor 118 may obtain information from and store data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may obtain information from and store data in memory that is not physically located on the WTRU 102, such as memory located on a server or home computer (not shown).

[0028] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to other components within the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0029] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or instead of information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from base stations (e.g., base stations 114a, 114b) and / or may determine its location based on the timing of signals received from two or more nearby base stations. It should be understood that the WTRU 102 may acquire location information using any suitable location determination method while remaining consistent with an embodiment.

[0030] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photos or videos), a Universal Serial Bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an internet browser, and the like.

[0031] 1C shows exemplary WLAN devices, one or more of which may be used to implement one or more of the features described herein operating in a WLAN system 150. The WLAN system 150 may be configured to implement one or more protocols of the IEEE 802.11 communications standard, which may include channel access schemes such as DSSS, OFDM, OFDMA, etc. The WLAN may operate in a mode, e.g., infrastructure mode, ad hoc mode, etc.

[0032] The WLAN system 150 may include, without limitation, an access point (AP) 152, a station (STA) 154, and a STA 156. The STA 154 and the STA 156 may be associated with the AP 152. A WLAN operating in infrastructure mode may comprise one or more APs that communicate with one or more associated STAs. The APs and the STAs associated with the APs may comprise a basic service set (BSS). For example, the AP 152, the STA 154, and the STA 156 may comprise a BSS 160. An extended service set (ESS) may comprise one or more APs (with one or more BSSs) and the STAs associated with the APs.

[0033] An AP may have access to and / or an interface to a distribution system (DS), which may be wired and / or wireless, and may carry traffic to and / or from the AP. Traffic originating outside the WLAN and destined for a STA within the WLAN may be received at an AP within the WLAN, which may transmit the traffic to the STA within the WLAN. Traffic originating at a STA within the WLAN and destined for a destination outside the WLAN may be transmitted to an AP within the WLAN, which may transmit the traffic to the destination.

[0034] As shown, AP 152 communicates with network 170. Network 170 communicates with server 180. Traffic between STAs in a WLAN can be transmitted through one or more APs. For example, a source STA (e.g., STA 156) can have traffic destined for a destination STA (e.g., STA 154). STA 156 can transmit traffic to AP 152, and AP 152 can transmit traffic to STA 154.

[0035] A WLAN can operate in ad-hoc mode. An ad-hoc mode WLAN is sometimes referred to as an independent BSS. In an ad-hoc mode WLAN, STAs can communicate directly with each other (e.g., STA 154 can communicate with STA 156 without the communication being routed through an AP).

[0036] IEEE 802.11 devices (e.g., IEEE 802.11 APs in a BSS) can use beacon frames to announce the presence of a WLAN network. An AP, such as AP 152, can transmit beacons on a channel, e.g., a fixed channel, such as a primary channel. STAs can use a channel, such as the primary channel, to establish a connection with the AP.

[0037] The STA and / or AP may use a carrier sense multiple access with collision avoidance (CSMA / CA) channel access mechanism. In CSMA / CA, the STA and / or AP may sense the primary channel. For example, if the STA has data to transmit, the STA may sense the primary channel. If the primary channel is detected to be busy, the STA may back off. For example, a WLAN or portion thereof may be configured so that one STA may transmit, for example, in a given BSS, at a given time. Channel access may include RTS and / or CTS signaling. For example, an exchange occurs between a request to send (RTS) frame, which may be sent by a transmitting device, and a clear to send (CTS) frame, which may be sent by a receiving device. For example, if an AP has data to send to a STA, the AP may send an RTS frame to the STA. If the STA is ready to receive data, the STA may respond with a CTS frame. The CTS frame may include a time value that may warn other STAs to refrain from accessing the medium while the AP that initiated the RTS may transmit its data. Upon receiving the CTS frame from the STA, the AP can transmit data to the STA.

[0038] Devices can reserve spectrum via the Network Allocation Vector (NAV) field. For example, in IEEE 802.11 frames, the NAV field can be used to reserve a channel for a period of time. A STA that wants to transmit data can set its NAV to be the time it can expect to use the channel. When a STA sets its NAV, it can set the NAV for the associated WLAN or a subset thereof (e.g., BSS). Other STAs can count down their NAV to 0. When the counter reaches a value of 0, the NAV function can indicate to other STAs that the channel is now available.

[0039] A device in a WLAN, such as an AP or a STA, may include one or more of the following: a processor, memory, a radio receiver and / or transmitter (e.g., which may be combined into a transceiver), one or more antennas, etc. The processor function may include one or more processors. For example, the processor may include one or more of a general-purpose processor, a special-purpose processor (e.g., a baseband processor, a MAC processor, etc.), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. One or more processors may or may not be integrated with each other. A processor (e.g., one or more processors, or a subset thereof) may be integrated with one or more other functions (e.g., other functions, such as memory). A processor may perform signal coding, data processing, power control, input / output processing, modulation, demodulation, and / or any other function that may enable a device to operate in a wireless environment, such as the WLAN of FIG. 1C. A processor may be configured to execute processor-executable code (e.g., instructions), including, for example, software instructions and / or firmware instructions. For example, a processor may be configured to execute computer-readable instructions contained on one or more of the processor (e.g., a chipset including a memory and a processor) or memories. Execution of the instructions may cause the device to perform one or more of the functions described herein.

[0040] The device may include one or more antennas. The device may utilize multiple-input multiple-output (MIMO) techniques. The one or more antennas may receive wireless signals. The processor may, for example, receive wireless signals via one or more antennas. The one or more antennas may transmit wireless signals (e.g., based on signals transmitted from the processor).

[0041] A device may have memory, which may include one or more devices for storing programming and / or data, such as processor-executable code or instructions (e.g., software, firmware, etc.), electronic data, databases, or other digital information. The memory may include one or more memory units. The one or more memory units may be integrated with one or more other functions (e.g., other functions included within the device, such as a processor). The memory may include read-only memory (ROM) (e.g., erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, and / or other non-transitory computer-readable media for storing information. The memory may be coupled to a processor. The processor may communicate with one or more entities of the memory, for example, via a system bus, directly, etc.

[0042] A WLAN in infrastructure basic service set (BSS) mode can have an access point (AP) for the basic service set and one or more stations (STAs) associated with the AP. The AP can have access to or interface with a distribution system (DS) or another type of wired / wireless network that can carry traffic within and outside the BSS. Traffic originating outside the BSS for a STA can arrive through the AP and be delivered to the STA. Traffic originating at a STA for a destination outside the BSS can be sent to the AP and then delivered to the respective destination. Traffic between STAs within the BSS can be sent through the AP, and a source STA can send traffic to the AP, which can deliver the traffic to the destination STA. Traffic between STAs within the BSS can be peer-to-peer traffic. Such peer-to-peer traffic can be sent directly between the source and destination STAs using, for example, Direct Link Setup (DLS) using IEEE 802.11e DLS or IEEE 802.11z Tunneled DLS (TDLS). A WLAN using an independent BSS mode may not have an AP and STAs may communicate directly with each other. This mode of communication may be called an ad-hoc mode.

[0043] Using the IEEE 802.11 infrastructure mode of operation, an AP can transmit beacons on a fixed channel, typically the primary channel. This channel can be 20 MHz wide and can be the operating channel of the BSS. This channel can also be used by STAs to establish connections with the AP. Channel access in IEEE 802.11 systems can be carrier sense multiple access with collision avoidance (CSMA / CA). In this mode of operation, STAs, including the AP, can sense the primary channel. If the channel is detected to be busy, the STA can back off. One STA can transmit at any given time in a given BSS.

[0044] Figure 2 shows that 802.11n (High Throughput) can support three PPDU formats: non-HT PPDU, HT mixed format PPDU, and HT Greenfield format PPDU. The 802.11n HT-SIG fields are shown in Table 1.

[0045] [Table 1-1]

[0046] [Table 1-2]

[0047] The IEEE 802.11ah Task Group was established to develop solutions for supporting WiFi systems in the sub-1 GHz (S1G) band. 802.11ah PHYs may be required to support 1, 2, 4, 8, and 16 MHz bandwidths. Support for 1 MHz and 2 MHz bandwidths may be mandatory for 802.11ah STAs.

[0048] Figure 3 shows an example of the S1G short format. Figure 4 shows an example of the SIG field in the S1G short format.

[0049] Figure 5 shows an example of an S1G long format PPDU. Figure 6 shows an example of a SIG-A field for a single-user transmission. Figure 7 shows an example of a SIG-A field for a multi-user transmission. Table 2 gives the SIG-B fields for the S1G long format.

[0050] [Table 2]

[0051] S1G 1MHz transmission can be mandatory. Figure 8 shows an example of a PPDU in the S1G 1M format. Figure 9 shows an example of the SIG field in the S1G 1M format.

[0052] In 802.11ac, a Very High Throughput (VHT) preamble may be defined to carry the required information for operating in single-user or multi-user modes. To maintain backward compatibility with non-VHT STAs, specific non-VHT fields (or legacy fields) may be defined so that they can be received by non-VHT STAs (e.g., to comply with Clause 17 or Clause 19). The non-VHT fields may be followed by VHT fields that are specific to VHT STAs. Figure 10 shows an example of an 802.11ac VHT mixed format packet.

[0053] Information that may be needed to interpret a VHT format packet may be carried by the VHT-SIG-A field. The VHT-SIG-A field may contain the fields listed in Table 3. The VHT-SIG-A field may contain a VHT-SIG-A1, which contains 24 data bits, as shown in Table 3.

[0054] [Table 3-1]

[0055] [Table 3-2]

[0056] The VHT-SIG-A field may contain the fields listed in Table 4. The VHT-SIG-A field may contain a VHT-SIG-A2 field, which contains 24 data bits as shown in Table 4.

[0057] [Table 4-1]

[0058] [Table 4-2]

[0059] VHT-SIG-A1 (Table 3) can be transmitted before VHT-SIG-A2 (Table 4). VHT-SIG-A symbols can be BCC coded at rate R=1 / 2, interleaved, and mapped to a BPSK constellation. The short training field (STF), long training field (LTF), and SIG field are sometimes referred to as the omni portion of the MU-MIMO preamble.

[0060] The information can be carried by the VHT-SIG-B field, which can be specifically related to providing MU-MIMO information to multiple simultaneous STAs. The VHT-SIG-B field can contain data bits as shown in Table 5.

[0061] [Table 5]

[0062] The concept of group ID (introduced by 802.11ac) can be utilized for DL ​​MU-MIMO transmissions, allowing an AP to address a group of STAs with a single ID. The group ID is contained within the VHT-SIG-A field (Table 4). An AP can assign a group ID to a STA using a group ID management frame. The group ID management frame can address an individual STA and can include a membership status array and a user location array.

[0063] FIG. 11 shows an example of a membership status array field.

[0064] FIG. 12 shows an example of a user position array field.

[0065] Null Data Packets (NDPs) (e.g., introduced by 802.11ah) can carry simple control / management information. The following frames can be defined: NDP Clear to Send (CTS) frame, NDP Contention-Free End (CF End) frame, NDP Power Save Poll (PS Poll) frame, NDP Acknowledgement (ACK) frame, NDP Block Acknowledgement (BA) frame, NDP Beamforming Report Poll frame, NDP Paging frame, and NDP Probe Request frame.

[0066] Preamble designs and associated procedures for simultaneous downlink and uplink multi-user transmissions are described below. WiFi systems have emphasized support for single-user transmissions. 802.11ac and 802.11ah can address improved downlink spectral efficiency by including support for downlink multi-user MIMO (DL MU-MIMO). Support for simultaneous uplink (UL) MU-MIMO transmissions may be required. Current designs for UL transmissions may (e.g., only) consider requirements for UL single-user (SU) MIMO. Systems and methods for use with simultaneous UL MU-MIMO transmissions may be provided.

[0067] A PPDU format that can be understood by both intended and unintended STAs, and both legacy and non-legacy STAs, may be required. For MU-MIMO operation, a PPDU format that supports time, space, and frequency resource allocation regions may be required.

[0068] A signaling field (SIG) may be required to detect and decode packets. In 802.11ac, the SIG field may have two parts: VHT-SIG-A (46 bits) and VHT-SIG-B (29 bits). VHT-SIG-A may be further subdivided into VHT-SIG-A1 (23 bits) and VHT-SIG-A2 (23 bits). The SIG field may provide an indication of frame attributes (including, for example, channel width and MCS). The SIG field may provide an indication of whether SU-MIMO or MU-MIMO operation is active. The VHT-SIG-B field may be specifically related to providing MU-MIMO information to multiple simultaneous STAs. An indication of the STA's group ID may be provided by the SIG field. The SIG field may contain non-trivial overhead for conveying control information to the receiver. If the SIG field is not decoded properly, it may affect the proper reception of the entire PPDU. The incorporation of PHY-based DL MU-MIMO and / or UL MU-MIMO and associated simultaneous transmissions may require an indication that indicates additional parameters to the receiver for proper reception. Systems, methods, and / or devices that enable this indication, including possible designs of new SIG fields, may be needed to enable operation in these modes. Given the overhead of SIG design in 802.11, reducing this overhead and improving the detection probability for operation in these modes may be beneficial.

[0069] The STF and LTF can be utilized for packet detection, time / frequency synchronization, and / or channel estimation initiation. The STF / LTF can be designed to better fit with simultaneous transmission implementations. The synchronization and channel estimation requirements for simultaneous transmissions may be different from single-user transmissions, and the STF / LTF can be redesigned.

[0070] The group ID can be in the range [0,63], with 0 / 63 indicating single-user transmission. Thus, up to 62 multi-user groups can be supported. A group can have a maximum of four users. With multiple simultaneous transmissions on both the DL and UL, and potentially multiple simultaneous transmission modes, the available number of group IDs may not be sufficient. Group ID management frames can be transmitted by the AP using unicast transmission. AP assignment of group IDs to STAs can be done sequentially and individually, which can result in inefficiencies that can adversely affect network spectral efficiency. If the AP is required to create a new group of STAs, it may need to reassign the STAs' group IDs. This can be done by transmitting a group ID management frame to (e.g., each) user in the group prior to the start of simultaneous transmissions, which can create undesirable inefficiencies and limitations.

[0071] Pilot designs for other simultaneous transmissions, which may include requirements for DL ​​and UL, may require definition of the pilot design.

[0072] Simultaneous multi-user transmission may require extra control frames to carry additional necessary signaling. The overhead of the control frames may reduce system efficiency. NDP packets, which may include (e.g., only include) a PHY header and may not include a MAC body, may be used to further reduce the overhead of the required control frames, thereby increasing system efficiency.

[0073] A generic PPDU format may be provided, which may require including legacy STF, LTF, and / or SIG fields, for example, to support multiple simultaneous transmission modes, while supporting backward compatibility with existing IEEE 802.11 specifications.

[0074] Figure 13 shows an exemplary PPDU format design. A high-efficiency SIG field (e.g., referred to herein as the hewSIG field) can be placed following the L-SIG field in the PPDU. The L-STF, L-LTF, L-SIG, and hewSIG fields can be transmitted and replicated on each 20 MHz channel. The fields can be transmitted using an omni-transmit antenna mode. For simultaneous downlink transmissions, a cyclic shift diversity (CSD) scheme can be used when multiple antennas are simultaneously utilized at the transmitter. For simultaneous uplink transmissions, CSD may not be utilized.

[0075] The transmission of the fields may depend on the backward compatibility supported by the system. For example, if backward compatibility with IEEE 802.11a / g is required, the subcarrier format, sequence, and / or CSD parameters (if applicable) may be related to those of the 802.11ac non-VHT portion transmission (e.g., may be identical to those of the 802.11ac non-VHT portion transmission). For example, the non-VHT portion may include a legacy portion of the preamble frame format (e.g., the non-VHT field shown in FIG. 10). If backward compatibility with IEEE 802.11a / g is not required but backward compatibility with 802.11ac / n is required, the subcarrier format, sequence, and / or CSD parameters (if applicable) may be identical to those of the 802.11ac VHT portion transmission.

[0076] The hewSIG field can be transmitted in a manner that allows for automatic detection from existing legacy mode, HT mixed mode, and / or VHT mode PPDUs. The MU mode can be included within the hewSIG field, which can indicate the specific MU mode utilized in the packet. The MU mode can indicate SU transmission, MU transmission using frequency division (OFDMA), MU transmission using spatial division (MU-MIMO), and / or MU transmission using time division (MU-TDMA). Figure 13 shows an 8us hewSIG; however, the hewSIG field can be of different time durations.

[0077] Depending on the MU mode conveyed in the hewSIG field, the hewSTF, hewLTF, and / or hewSIGB fields may have different variations. A PPDU that supports multiple simultaneous transmission modes may be a high-efficiency PPDU, which may be referred to as a high-efficiency WLAN (HEW) PPDU.

[0078] The HEW PPDU can be utilized, for example, to support UL MU-MIMO. Figure 13 shows an exemplary HEW PPDU design, with uplink transmissions operated on an 80 MHz channel. Other channel bandwidths and other numbers of channels can be utilized. Each UL MU-MIMO STA can transmit the L-STF, L-LTF, L-SIG, and / or hewSIG fields using a 20 MHz transmission format, which can overlap on each 20 MHz channel. Other channel bandwidths can be supported.

[0079] FIG. 14 shows an example PPDU design, sometimes referred to as Design 1, in which an UL MU-MIMO STA (e.g., all UL MU-MIMO STAs) may transmit a complete sequence of L-STF and L-LTF in a subchannel (e.g., all subchannels). The UL MU-MIMO STAs may transmit a complete sequence of L-STF and L-LTF using cyclic shift diversity (CSD) between users. For example, the complete sequence may be a complete preamble sequence including an L-STF and L-LTF for each antenna. A signaling field, such as a SIG, may follow. The L-SIG may carry legacy PHY layer signaling and may be the same between UL STAs. The cyclic shift values ​​between multiple users may be different for different types of channels. In the case where one UL MU-MIMO STA has more than one antenna, transmissions from that STA through multiple antennas may utilize the CSD scheme and related parameters defined for the single-user case. The UL MU-MIMO STAs can transmit the complete sequence of L-STF and L-LTF without cyclic shift diversity (CSD) between users. The hewSIG field can be transmitted using the same set of CSD values ​​utilized for L-STF and L-LTF. The hewSIG field can be the same among some (e.g., all) UL STAs, and it can contain common information for this UL MU-MIMO transmission.

[0080] The transmitted legacy fields may not be spatially separable, but they may be identical so that they are seen by the receiver as multipath replicas of the same signal. The HEW-based fields may be spatially separable (e.g., using a P-matrix on the hewLTF) so that the receiver can decode the hewSIGB and subsequent data.

[0081] 15 shows an example PPDU design, sometimes referred to as Design 2, in which a user (e.g., only one user) may transmit the L-STF, L-LTF, L-SIG, and / or hewSIG fields. The user may be the first user defined by the UL MU-MIMO group, and the AP assigns one user to transmit, such as by using a control frame, prior to the UL MU-MIMO transmission. Legacy signals may be spatially separable by transmitting them from a single STA.

[0082] The transmission of the L-STF, L-LTF, L-SIG, and hewSIG fields can be subdivided in the frequency domain. For example, if N users are transmitting with UL MU-MIMO, user 1 can transmit on subcarrier indices {K, K+N, K+2N, ...}, while user N can transmit on subcarrier indices {K+N-1, K+2N-1, K+3N-1, ...}.

[0083] The hewSTF / hewLTF fields can be used for multi-user synchronization and / or channel estimation. The hewSTF / hewLTF fields can be transmitted in a manner that allows the receiver (AP) to distinguish between them.

[0084] Figure 16 shows an exemplary hewSTF / hewLTF design for UL MU-MIMO. For example, four users can transmit simultaneously to an AP using UL MU-MIMO. After transmitting the legacy LTF / STF / SIG and hewSIG fields, each STA can transmit its hewSTF field. The duration of the transmitted hewSTF field, e.g., the number of OFDM symbols N_stf, depends on the number of UL MU-MIMO users N_user and the number of data streams for each user N_sts.

[0085]

number

[0086] In the four-user example, each user may have one data stream, and there may be four OFDM symbols utilized for the hewSTF field. Each user may utilize one OFDM symbol to transmit its hewSTF. User 1 / STA1 may transmit its hewSTF in the first OFDM symbol, User 2 / STA2 may transmit its hewSTF in the second OFDM symbol, and so on. The order of hewSTF transmission may be implicitly conveyed by the position field within the group ID. The order of hewSTF transmission may be explicit by other group ID mechanisms.

[0087] In an exemplary design, hewLTF may be transmitted using N_ltf OFDM symbols, where N_ltf is a function of the number of UL MU-MIMO users, N_user, and the number of data streams for each user, N_sts.

[0088]

number

[0089] In the four user example, each user may have one data stream and there may be four OFDM symbols utilized as the hewLTF field: User 1 / STA1 may transmit its hewLTF in the first OFDM symbol, User 2 / STA2 may transmit its hewLTF in the second OFDM symbol, and so on.

[0090] Figure 17 shows a hewSTF / hewLTF design for UL MU-MIMO. A user can transmit a hewLTF on an OFDM symbol (e.g., every OFDM symbol), but can vary the LTF transmission, for example, using a P-matrix, to orthogonalize the transmission. Overlapping STFs can be used with a receiver that views transmissions from multiple STAs as multipath arrivals of the STF signal.

[0091] 18 illustrates a design of the hewLTF. In this design, the hewSTF may remain the same as that described above. The number of OFDM symbols used to transmit the hewLTF may be the same or may be fixed at 1, 2, 4, 6, or 8 OFDM symbols. Scenarios involving transmission of a number of data not equal to one of these numbers may use the next highest number (e.g., in the case of 3 / 5 / 7 data streams from a user, 4 / 6 / 8 OFDM symbols are utilized for the hewLTF, respectively).

[0092] In an example with four users and one data stream, there may be four OFDM symbols utilized for hew LTF transmission per user. Different users may occupy different frequency domain subcarriers. As an example, in FIG. 18, the frequency domain channel may be partitioned into eight subchannels. The following allocation may be used: User 1 / STA1 transmits hew LTF on subchannels 1 and 5, User 2 / STA2 transmits hew LTF on subchannels 2 and 6, User 3 / STA3 transmits hew LTF on subchannels 3 and 7, and User 4 / STA4 transmits hew LTF on subchannels 4 and 8.

[0093] The channel can be partitioned into four sub-channels in a localized or distributed manner. Each user / STA can transmit (e.g., only transmit) a hewLTF sequence on one or several sub-channels. A hewLTF sequence can be defined for the entire channel. Each user / STA can follow one or more of the following to transmit a hewLTF:

[0094] The STA can use a predefined hewLTF sequence, which it can modulate into the frequency domain.

[0095] The STA can check the group ID and identify its position within the group. Based on this information, the STA can apply a frequency domain filtering function to the modulated hewLTF field. The frequency domain filtering function can be defined as follows:

[0096]

number

[0097] where k is the subcarrier index, n is the data stream index, n=1,...,N_ltf. In the case where each user has one data stream, n may be the same as the user index. sub_channel(n) may be the set of subcarriers allocated to the nth stream for hewLTF transmission. sub_channel(n) may be defined using the following example: sub_channel(n)=data_index(n:N ltf :end) where data_index is the set of subcarriers used for data transmission. For example, when using 20 MHz transmission, data_index={-28:-22;-20:-8;-6:-1;1:6;8:20;22:28} is.

[0098] A small number of subcarriers, e.g., N_sub, can be pre-grouped together and subchannels assigned based on the pre-grouped subcarrier groups. In cases where the total number of subcarriers is not divisible by N_sub × N_ltf (e.g., using 20 MHz transmission), 52 data subcarriers (N_dc = 52) are utilized. For example, with two subcarrier pre-groups, if N_ltf = 4, the last few subcarriers cannot be pre-grouped because 52 is not divisible by 8 (2 × 4).

[0099] The sub-channels are

[0100]

number

[0101] can be redefined as follows:

[0102] For example, if N_sub=2, N_ltf=4, and 20MHz transmission, sub_channel(1)={-28,-27,-19,-18,-11,-10,-2,-1,8,9,16,17,25} sub_channel(2)={-26,-25,-17,-16,-9,-8,1,2,10,11,18,19,26} sub_channel(3)={-24,-23,-15,-14,-6,-5,3,4,12,13,20,22,27} sub_channel(4)={-22,-20,-13,-12,-4,-3,5,6,14,15,23,24,28} is.

[0103] The two sub_channel and data_index designs are examples.

[0104] Figure 19 shows a hewSTF / hewLTF design. The hewSTF may be as described above. The hewLTF transmission may have the same number of hewLTF symbols as described with respect to Figure 18. The frequency channel may be partitioned into multiple subchannels, and each data stream of each STA may utilize one subchannel. Instead of transmitting the hewLTF on the same subchannel for the hewLTF symbols, the hewLTF of each data stream may be transmitted alternately. Each user / STA may use one or more of the following to transmit the hewLTF:

[0105] The STA may use a predefined hewLTF sequence, which the STA may modulate into the frequency domain.

[0106] The STA can check the group ID and identify its position within the group. Based on this information, the STA can apply a frequency domain filtering function to the modulated hewLTF field. The frequency domain filtering function can be defined as follows:

[0107]

number

[0108] where k is the subcarrier index, n is the data stream index, n=1,...,N_ltf. In the case where each user has one data stream, n is the same as the user index, and m is the hewLTF symbol index, m=1,...,N_ltf. sub_channel(m,n) may be the set of subcarriers allocated to the nth stream for hewLTF transmission. sub_channel(m,n) may be defined using the following example: sub_channel(m,n)=data_index(m+n:N ltf :end) where data_index is the set of subcarriers used for data transmission. For example, when using 20 MHz transmission, data_index={-28:-22;-20:-8;-6:-1;1:6;8:20;22:28} is.

[0109] Alternatively, sub_channel and data_index may use the second design described with reference to FIG.

[0110] With the exemplary design of hewSTF / hewLTF for UL MU-MIMO (e.g., with reference to FIG. 19 ), it may be possible to utilize localized sub-channelization for hewLTF transmission.

[0111]

number

[0112] It can be designed as follows.

[0113] For example, if N_sub=2, N_ltf=4, and 20MHz transmission (N_dc=52), sub_channel(1,1)=sub_channel(2,4)=sub_channel(3,3)=sub_channel(4,2)={-28:-22;-20:-15} sub_channel(1,2)=sub_channel(2,1)=sub_channel(3,4)=sub_channel(4,3)={-14:-8;-6:-1} sub_channel(1,3)=sub_channel(2,2)=sub_channel(3,1)=sub_channel(4,4)={1:6;8:14} sub_channel(1,4)=sub_channel(2,3)=sub_channel(3,2)=sub_channel(4,1)={15:20;22:28} is.

[0114] Referring to Figure 20, an exemplary PPDU design for OFDMA transmissions using a subchannel size of 20 MHz or greater is shown. This PPDU format may be referred to as a long OFDMA PPDU. This design allows for backward compatibility with 802.11a / g or support for beamforming. These implementations can be applied to both uplink and downlink OFDMA transmissions. Exemplary OFDMA PPDU designs may be as shown in Figures 16 and 21. The AP can select the OFDMA PPDU frame format based on the capabilities of the STAs, whether beamforming is supported, and / or whether the system is required to be backward compatible with previous specifications.

[0115] The long OFDMA PPDU frame format can be used when backward compatibility to 802.11a / g or beamforming support is required and can include legacy estimation and signaling (L-STF, L-LTF, and L-SIG). The short OFDMA PPDU frame format can be used when backward compatibility to 802.11n is required and beamforming support is not required and can include only high throughput estimation and signaling (HT-STF, HT-LTF, and HT-SIG).

[0116] Figure 21 shows an example PPDU design for OFDMA transmission using a subchannel size of 20 MHz or greater. This PPDU format can be a short OFDMA PPDU. This design allows for backward compatibility with 802.11n, and beamforming is not supported.

[0117] 22 illustrates an exemplary OFDMA PPDU format selection (e.g., long / short). One or more of the following may apply:

[0118] The AP may check STA capabilities. The STA may be a STA with which the AP is associated. The AP may check STA capabilities using a beacon (e.g., the AP may not be associated with the STA). The STA's capability to support short OFDMA PPDUs may be exchanged through association or beacons (e.g., carried in an association request frame, association response frame, probe response frame, beacon frame, etc.). For example, the AP may check the STA's capability field, which may indicate support for long and / or short OFDMA PPDU preambles. A long OFDMA PPDU may be required for STAs (e.g., all STAs) that support OFDMA operation. If the STAs (e.g., at least one STA) involved in an upcoming DL OFDMA transmission do not support short OFDMA PPDUs, the AP may decide to use long preambles. If all STAs support the short PPDU format, short preambles may be used.

[0119] The AP may check whether the system is required to support first-generation legacy devices, which may be 802.11a / g, and / or second-generation legacy devices, which may be 802.11n / ac. The check may include checking operator capabilities. Checking the operator capabilities for the system may include determining whether the AP has capabilities that can support legacy devices. These capabilities may determine how to treat STAs prior to association. If 11a / g needs to be supported (e.g., for a STA associated with an upcoming DL OFDMA transmission), the AP may select a long OFDMA PPDU format.

[0120] The AP can check whether the upcoming OFDMA transmission includes any beamforming or precoding transmission, and if so, the AP can select the long OFDMA PPDU format; otherwise, the AP can select the short OFDMA PPDU format.

[0121] In the case of UL OFDMA transmission, the AP can inform the STAs performing OFDMA transmission of the selected PPDU format. For pending UL transmissions, the AP can inform the STAs of the PPDU format to use for the UL transmission.

[0122] 23 shows an exemplary OFDMA PPDU design using a subchannel size of less than 20 MHz that can be backward compatible with, for example, 802.11a / g and can support beamforming or other precoder transmissions. With this design, the L-STF, L-LTF, L-SIG, and / or hewSIG fields can be transmitted over the entire bandwidth.

[0123] These fields can be transmitted over the minimum required bandwidth supported by the current 802.11 standard and repeated over the entire bandwidth. For example, if an AP is operating on a 40 MHz channel and the minimum required bandwidth supported is 20 MHz, the above-described fields can be transmitted on the 20 MHz channel and repeated, with or without phase rotation, on a second 20 MHz channel. In the case of uplink OFDMA, the difference between the arrival times of transmissions from multiple STAs can be smaller than the guard interval (e.g., so that they appear similar to the effects of a multipath channel on a single signal). In the case of uplink OFDMA, the hewSIG can be such that it indicates a change to sub-channelized transmission with detailed signaling information moved to the hewSIGB field.

[0124] Following the hewSIG field, a set of dedicated fields may be transmitted on each subchannel. The set of dedicated fields may include a hewSTF, a hewLTF, and / or a hewSIGB field. The dedicated fields may be beamformed or precoded on a per-user basis. The hewSIGB field may contain information dedicated to one user. This design is sometimes referred to as a long OFDMA PPDU format.

[0125] FIG. 24 shows an exemplary short OFDMA PPDU format that has a smaller preamble overhead, can be backward compatible with 11ac / n users (e.g., backward compatible only with such users and not with earlier generation users), and cannot support beamforming or other precoding schemes. This design may be a short OFDMA PPDU format. A first portion that can be utilized to support backward compatibility with prior specifications may include one set of STF, LTF, and SIG fields, and this portion may be decodable by legacy devices (e.g., 11ac / n users). When using 20 MHz and 40 MHz transmissions, this set may be associated with (e.g., be identical to) the HT-STF, HT-LTF, and HT-SIG defined in 802.11n. When using 80 MHz or higher transmission, these fields can be transmitted over the entire bandwidth and the VHT-STF, VHT-LTF, and VHT-SIGB formats can be used. When these fields are transmitted over a 20 MHz channel and are repeated over the entire bandwidth, the HT-STF, HT-LTF, and HT-SIG formats can be utilized.

[0126] The hewSIG field can be considered part of the HEW transmission and cannot be decoded by legacy devices. However, it can be transmitted according to the same wavelength and subcarrier format as the LTF field transmitted before it. The hewSIG field can contain information about the upcoming OFDMA transmission that is common to users. The hewSIGB field can follow the hewSIG field and contain information specific to each OFDMA user.

[0127] Figure 25 shows a short OFDMA PPDU format. The subchannel size can be 20 MHz or larger, can be backward compatible with 802.11ac / n, and does not support beamforming. This design is similar to that shown in Figure 24, however, here the dedicated hewSIGB field can be omitted and the necessary information can be included in the hewSIG field. The AP can select either the long format or the short format for OFDMA transmission. The selection can be as shown in Figure 22.

[0128] Figure 26 shows an example SIG field transmission design for the hewSIG field, in which two OFDM symbols are utilized. Transmission and auto-detection of the hewSIG field can be provided. To enable auto-detection of the HEW signal, the hewSIG can include x OFDM symbols, where the first symbol can be rotated 90 degrees relative to the L-SIG and the second symbol can be rotated 90 degrees relative to the first axSIG symbol, and the rotation can continue across x OFDM symbols. This can enable auto-detection of the HEW signal and distinction from legacy mode, HT mixed mode, and / or VHT mode preambles. In an example in which the hewSIG field consists of two OFDM symbols, Figure 26 and Table 6 show how transmission and auto-detection of the hewSIG field can be implemented.

[0129] For example, assume that the BPSK signal is designated as +1 and the rotated BPSK signal is designated as -1, see the HEW autodetection in Table 6.

[0130] [Table 6]

[0131] The hewSIG field can be common for transmission modes (e.g., all transmission modes). The hewSIG field can include a new parameter used to indicate simultaneous transmission mode or multi-user transmission mode, MU mode. Exemplary MU mode values ​​are shown in Table 7.

[0132] [Table 7]

[0133] The hewSIG field may include one or more of the following subfields: MU mode, Group ID (e.g., different sets of Group IDs may be utilized based on the MU mode. For example, if the MU mode indicates OFDMA transmission, the Group ID may be interpolated), Direction Bit (1 bit), Bandwidth (BW) (More bandwidths may be supported in addition to 20 MHz, 40 MHz, 80 MHz, 160 MHz / 80+80 MHz, e.g., 60 MHz, 40 MHz+40 MHz; 3 bits), Doppler (1 bit, to support traveling pilots), or NDP Indication (indicates an NDP packet (with an NDP packet, the hewSIG field may be redundant since there is no data to be transmitted)).

[0134] The hewSIG field can have multiple subchannels. The hewSIG field can be transmitted using the minimum required channel bandwidth and can be repeated over the entire band if the operating bandwidth is greater than the minimum required bandwidth.

[0135] If the operating bandwidth is greater than the minimum required bandwidth, more information can be carried on the excess bandwidth. The hewSIG field can be different for each subchannel (for this purpose, a subchannel refers to a channel with a minimum required bandwidth). A single bit in the hewSIG field transmitted over the primary subchannel can be used to indicate that the hewSIG fields of other subchannels can contain different information than the primary subchannel.

[0136] The hewSIGB field can be used to carry user-specific information such as MCS, interleaving method, beamforming or MIMO mode with multiple space-time streams, method of feedback, etc.

[0137] A mechanism for group ID may be provided. A supergroup ID may be provided for different MU modes. For example, the AP may maintain different groups for different MU modes and / or uplink / downlink transmissions. The AP may maintain separate groups for DL ​​MU-MIMO, UL MU-MIMO, DL OFDMA, UL OFDMA, DL MU-time, and UL MU-time. The supergroup ID may consist of one or more of a multi-user mode indicator (3 bits), i.e., DL MU-MIMO group, UL MU-MIMO group, DL OFDMA group, UL OFDMA group, DL MU-time group, and / or UL MU-time group, or a group ID (6 bits), i.e., reusing the existing 64-bit group ID method in legacy systems. STAs may have the same group ID, but this may indicate different groups based on the specific multi-user mode.

[0138] The super group ID can consist of one or more of the following: a transmission direction bit (1 bit), i.e., uplink or downlink; a group type (3 bits), i.e., OFDMA / OFDMA-based transmission, MU-MIMO-based transmission, TDMA-based transmission; or a group ID (6 bits), i.e., reusing the existing 64-bit group ID method in legacy systems.

[0139] The Super Group ID can consist of one or more of the following: a multi-user mode indicator (2 bits), i.e., MU-MIMO, OFDMA, MU-Time, SU; a direction bit (1 bit), i.e., DL, UL; or a Group ID (6 bits), i.e., a reuse of the existing 64-bit Group ID method in legacy systems.

[0140] Broadcasting and efficient allocation of group IDs can be provided. A group ID management frame that assigns users to groups can be broadcast from the AP and includes the group ID and the MAC address of the STA in the new group to be attached. A 2-bit field can be used to indicate one or more of the following: New Group, which can set up a new group; Add to Group, which can add a STA to a group while maintaining existing members of the group; Remove from Group, which can remove a STA from a group while maintaining the remaining members in the group; or Temporary Replacement, which can temporarily replace a specific member of a group. The duration can be for the next x transmissions or can be permanent. In this case, the replaced member can be indicated by an index as opposed to using its MAC address. This can allow transmission to a different STA in cases where one member of the group does not have any data to send. Listed STAs can be added to or removed from a group more efficiently.

[0141] For downlink transmission, the AP can reuse existing pilot formats. When using MU-MIMO transmission mode, the AP can precode the pilots in the same way that it precodes data carriers. When using DL OFDMA transmission, a STA as a receiver can perform phase tracking using pilots across the entire band (e.g., not just pilots in its dedicated subchannel). When using UL MU-MIMO, the pilots can be designed in an orthogonal manner so that the AP can easily distinguish between pilots for each user. When using UL OFDMA, the design can be adapted so that each STA has enough pilots for phase tracking (especially when a small subchannel size, such as 10 MHz or 5 MHz, is used).

[0142] UL OFDMA transmissions can utilize traveling pilots (e.g., pilot positions are swapped when the OFDM symbol index is changed). The traveling pilot swapping function can be kept the same or can vary across multiple subchannels. The system can use time-varying orthogonal pilot patterns, where the pilot positions do not change but the pilot symbols change over time.

[0143] Pilot locations can remain static, but the system can allow (e.g., each) UL OFDMA user to transmit pilots over the entire bandwidth, rather than being limited to its own subchannel. In order for the receiver (AP) to distinguish pilots from different users, the pilots can be transmitted in an orthogonal manner. A set of orthogonal sequences can be defined, and users are assigned sequences.

[0144] In dense networks, with overlapping BSSs, pilot transmissions in one BSS can have a negative impact (cause interference) in other BSSs. Cross-AP pilot design can be used, in which pilot positions of one AP are configured to avoid pilot positions of another AP. Varying pilot symbol energy relative to data symbol energy can help mitigate the effects of inter-AP pilot interference.

[0145] An NDP design for MU control frames can be provided. For UL multi-user simultaneous transmissions, the AP may need to poll multiple stations to schedule uplink transmissions, and therefore there may be an extra frame exchange before the actual UL MU transmission. A set of defined NDP frames can be provided that can be utilized for MU control frames.

[0146] Figure 27 shows an exemplary uplink MU channel access. In this example, an MU poll frame, an uplink response frame (ULR), and an MU schedule frame are introduced for MU transmission. NDP frame formats for these frames can be provided. For example, one or more of the following fields can be added to the NDP frame: Direction (1 bit) indicating the direction of transmission; MU mode (2 or 3 bits) indicating the multi-user transmission type, such as DL MU-MIMO group, UL MU-MIMO group, DL OFDMA group, UL OFDMA group, DL MU-time group, and / or UL MU-time group (if the direction bit is included, a 2-bit MU mode can be used; otherwise, a 3-bit MU mode can be used); Group ID (6 bits), i.e., a field indicating the subgroup ID; or NDP type, i.e., a field indicating the type of NDP transmission; NDP MU poll; NDP MU response frame; and NDP MU schedule frame.

[0147] While features and elements have been described above in specific combinations, those skilled in the art will understand that each feature or element can be used alone or in any combination with other features and elements. In addition to the 802.11 protocol described herein, the features and elements described herein may be applicable to other wireless systems. While the features and elements described herein have been described for uplink operation, the methods and procedures may also be applied to downlink operation. While SIFS has sometimes been used herein to indicate various frame intervals, other frame intervals, such as RIFS or other agreed-upon time intervals, may apply. Additionally, the methods described herein may be implemented in a computer program, software, or firmware embodied in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random-access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor in conjunction with software may be used to implement a radio frequency transceiver for use in a WTRU, a terminal, a base station, an RNC, or any host computer. [Industrial Applicability]

[0148] The present invention can be generally applied to wireless communication systems.

Claims

1. a processor configured to determine a number of symbols to be used for a high efficiency (HE) long training field (HE LTF) based on a number of space-time streams associated with high efficiency (HE) wireless local area network (WLAN) communications, the number of symbols to be used for the HE LTF comprising 1, 2, 4, 6, or 8 symbols, and on the condition that the number of space-time streams is equal to 3, 5, or 7, the processor is configured to determine the number of symbols to be the next higher number than the number of space-time streams; a transmitter configured to send the HE LTF over the determined number of symbols; A station characterized by comprising:

2. 2. The station of claim 1, wherein the number of space-time streams is a total number of space-time streams for multi-user multiple-input multiple-output (MU-MIMO) communications.

3. 10. The station of claim 1, wherein the processor is further configured to determine a group identifier and identify a location of a device in a group associated with the group identifier.

4. determining, by a mobile station, a number of symbols to be used for a high efficiency (HE) long training field (HE LTF) based on a number of space-time streams associated with a high efficiency (HE) wireless local area network (WLAN) communication, wherein the number of symbols to be used for the HE LTF includes 1, 2, 4, 6, or 8 symbols, and the number of symbols is the next higher number than the number of space-time streams, provided that the number of space-time streams is equal to 3, 5, or 7; sending, by the mobile station, the HE LTF over the determined number of symbols; A method comprising:

5. 5. The method of claim 4, wherein the number of space-time streams is the total number of space-time streams for a multi-user multiple-input multiple-output (MU-MIMO) user.

6. determining a group identifier and identifying the location of the device in the group associated with said group identifier; The method of claim 4 further comprising:

7. 10. The station of claim 1, wherein the processor determines that the number of symbols is equal to the number of space-time streams, provided that the number of space-time streams is equal to 1, 2, 4, 6, or 8.

8. 2. The station of claim 1, wherein the transmitter is configured to send the HE LTF in the communication using a set of subcarriers associated with the number of space-time streams.

9. determining that the number of symbols is equal to the number of space-time streams, where the number of space-time streams is equal to 1, 2, 4, 6, or 8; The method of claim 4 further comprising:

10. 5. The method of claim 4, wherein the HE LTF is sent in the communication using a set of subcarriers associated with the number of space-time streams.

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