WO2017011274A1

WO2017011274A1 - Methods for resource allocation of an ofdma wlan system

Info

Publication number: WO2017011274A1
Application number: PCT/US2016/041397
Authority: WO
Inventors: Guodong Zhang; Hanqing Lou; Oghenekome Oteri; Xiaofei Wang; Fengjun Xi; Robert L. Olesen; Frank La Sita; Monisha Ghosh
Original assignee: Interdigital Patent Holdings, Inc.
Priority date: 2015-07-10
Filing date: 2016-07-07
Publication date: 2017-01-19
Also published as: TW201713088A

Abstract

Systems, methods, and instrumentalities are disclosed for SIG Design for OFDMA in WLAN Systems. A protocol data unit (PDU), e.g., a medium access control (MAC) PDU, may be transmitted. Data may be mapped to a plurality of OFDM symbols of the PDU. Each of the plurality of OFDM symbols may be associated with a first duration and a first length of data. A second length of data to be transmitted in a last OFDM symbol of the plurality of OFDM symbols may be determined to be less than the first length of data. The last OFDM symbol may be modified, for example, based on the second length of data, from the first duration to a second duration. The second duration may be ¼, ½, or ¾ of the first duration. An indication of the second duration of the last OFDM symbol may be sent.

Description

METHODS FOR RESOURCE ALLOCATION OF AN OFDMA WLAN SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. provisional patent application nos.

62/191,078, filed July 10, 2015, and 62/250,438, filed November 3, 2015, which are incorporated herein by reference in their entireties.

BACKGROUND

[0002] A Wireless Local Area Network (WLAN) may have multiple modes of operation, such as an Infrastructure Basic Service Set (BSS) mode and/or an Independent BSS (IBSS) mode. A WLAN in Infrastructure BSS mode may have an Access Point (AP) for the BSS. One or more wireless transmit receive units (WTRUs), e.g. , stations (STAs), may be associated with an AP. An AP may have access to and/or an interface with a Distribution System (DS) or other type of wired/wireless network that carries traffic in and out of a BSS. Traffic to STAs that originates from outside a BSS may arrive through an AP, which may deliver the traffic to the STAs. In certain WLAN systems STA to STA communication may take place. In certain WLAN systems an AP may act in the role of a STA. Beamforming may be used by WLAN devices. Current beamforming techniques may be limited. Resources may be allocated in a WLAN.

SUMMARY

[0003] Systems, methods, and instrumentalities are disclosed for dynamic packing, e.g., orthogonal frequency division multiple access (OFDMA) in WLAN Systems. A protocol data unit (PDU), e.g. , a medium access control (MAC) PDU, may be transmitted. The PDU may be a physical layer convergence procedure (PLCP) PDU (PPDU). Data may be mapped to a plurality of OFDM symbols of the PDU. Each of the plurality of OFDM symbols may be associated with a first duration and/or a first length of data. The first length of data may be associated with a data length (e.g., a maximum data length) that can be carried within each of the plurality of OFDM symbols. A second length of data to be transmitted in a last OFDM symbol of the plurality of OFDM symbols may be determined to be less than the first length. For example, the second length of data may be determined to be ¼, ½, or ¾ of the first length of data. The last OFDM symbol may be modified, for example, based on the second length of data, from the first duration to a second duration. The second duration may be ¼, ½, or ¾ of the first duration. The last OFDM symbol may be modified to ¼ of the first duration when the second length of data is less than or equal to ¼ of the first length of data. The last OFDM symbol may be modified to ½ of the first duration when the second length of data is greater than ¼ the first length of data and less than or equal to ½ the first length of data. The last OFDM symbol may be modified to ¾ of the first duration when the second length of data is greater than ½ of the first length of data and less than or equal to ¾ of the first length of data. The first length of data and/or the second length of data may be associated with a number of available carriers.

[0004] An indication of the second duration of the last OFDM symbol may be sent. The indication may indicate that the second duration of the last OFDM symbol is ¼, ½, or ¾ of the first duration. The indication of the second length of the last OFDM symbol may be indicated as ¼, ½, or ¾ via a PHY header or a MAC header. The indication may indicate that the second duration is equal to the first duration when the second length of data is greater than ¾ of the first length of data. A periodic symbol may be created based on the second length of the last OFDM symbol. The last OFDM symbol may be reduced from the first length to the second length by removing excessive padding using a fast Fourier transform (FFT)/inverse FFT (IFFT) relationship Modifying the last OFDM symbol from the first duration to the second duration may include removing one or more redundant periods that result from using the IFFT relationship.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 A illustrates exemplary wireless local area network (WLAN) devices.

[0006] FIG. IB is a diagram of an example communications system in which one or more disclosed features may be implemented.

[0007] FIG. 1C depicts an exemplary wireless transmit/receive unit, WTRU.

[0008] FIG. 2 is an example of OFDMA numerology for a 20 MHz building block.

[0009] FIG. 3 is an example of OFDMA numerology for a 40 MHz building block.

[0010] FIG. 4 is an example of OFDMA numerology for an 80 MHz building block. [0011] FIG. 5 is an example power spectrum density of a partially loaded OFDM signal with RF I/Q imbalance.

[0012] FIG. 6 is an example of Bit Error Rate (BER) performance for an interfered signal.

[0013] FIG. 7 is an example format of a RU allocation field.

[0014] FIG. 8 is an example format of a RU allocation field.

[0015] FIG. 9 is an example of tone plans for a 20 MHz band and RU unit labels.

[0016] FIG. 10 is an example of distributed RU signaling with a fixed STA information size.

[0017] FIG. 11 is an example of distributed RU scheduling.

[0018] FIG. 12 is an example of contiguous RU signaling with fixed STA Info size.

[0019] FIG. 13 is an example of contiguous RU scheduling.

[0020] FIG. 14 is an example of contiguous RU allocation with multiple RU sets.

[0021] FIGS. 15A and 15B are examples of contiguous RU signaling field designs with variable STA Info size.

[0022] FIG. 16 is an example of flat RU signaling.

[0023] FIGS. 17A and 17B are examples of flat RU signaling.

[0024] FIGS. 18 A and 18B are examples of flat RU signaling.

[0025] FIGS. 19A and 19B are examples of flat RU signaling.

[0026] FIG. 20 is an example of limited RU allocations for a 20 MHz band.

[0027] FIG. 21 is an example of type 1 signaling that explicitly signals a number of STAs.

[0028] FIG. 22 is an example of type 1 signaling that explicitly signals a number of STAs.

[0029] FIG. 23 is an example of type 2 signaling that implicitly signals a number of STAs

[0030] FIG. 24 is an example of type 2 signaling that implicitly signals a number of STAs

[0031] FIG. 25 is an example of type 2 signaling that implicitly signals a number of STAs

[0032] FIG. 26 is an example of a minimum allowable bandwidth.

[0033] FIG. 27 is an example of a limited number of allowable bandwidths.

[0034] FIG. 28 is an example of a resource allocation frame format.

[0035] FIG. 29 is an example of parameters announced by a resource allocation frame to indicate resource allocation in future sessions.

[0036] FIG. 30 is an example of narrow band allocation for Internet of Things (IoT) operation.

[0037] FIG. 31 is an example of symmetric RU allocation.

[0038] FIG. 32 is an example of dynamic padding in every fourth sub-carrier (1/4 data).

[0039] FIG. 33 is an example of dynamic padding in every second sub-carrier (1/2 data).

[0040] FIG. 34 is an example of dynamic padding where two truncated OFDM symbols of length ¼ and length ½ may be transmitted (3/4 data). [0041] FIG. 35 is an example of dynamic padding in OFDMA transmission.

DETAILED DESCRIPTION

[0042] A detailed description of illustrative embodiments will now be described with reference to the various Figures. Although this description provides a detailed example of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application.

[0043] FIG. 1 A illustrates exemplary wireless local area network (WLAN) devices. One or more of the devices may be used to implement one or more of the features described herein. The WLAN may include, but is not limited to, access point (AP) 102, station (STA) 110, and STA 112. STA 110 and 112 may be associated with AP 102. The WLAN may be configured to implement one or more protocols of the IEEE 802.11 communication standard, which may include a channel access scheme, such as DSSS, OFDM, OFDMA, etc. A WLAN may operate in a mode, e.g. , an infrastructure mode, an ad-hoc mode, etc.

[0044] A WLAN operating in an infrastructure mode may comprise one or more APs communicating with one or more associated STAs. An AP and STA(s) associated with the AP may comprise a basic service set (BSS). For example, AP 102, STA 110, and STA 112 may comprise BSS 122. An extended service set (ESS) may comprise one or more APs (with one or more BSSs) and STA(s) associated with the APs. An AP may have access to, and/or interface to, distribution system (DS) 116, which may be wired and/or wireless and may carry traffic to and/or from the AP. Traffic to a STA in the WLAN originating from outside the WLAN may be received at an AP in the WLAN, which may send the traffic to the STA in the WLAN. Traffic originating from a STA in the WLAN to a destination outside the WLAN, e.g. , to server 118, may be sent to an AP in the WLAN, which may send the traffic to the destination, e.g. , via DS 116 to network 114 to be sent to server 118. Traffic between STAs within the WLAN may be sent through one or more APs. For example, a source STA (e.g. , STA 110) may have traffic intended for a destination STA (e.g. , STA 112). STA 110 may send the traffic to AP 102, and, AP 102 may send the traffic to STA 112.

[0045] A WLAN may operate in an ad-hoc mode. The ad-hoc mode WLAN may be referred to as independent basic service set (IBBS). In an ad-hoc mode WLAN, the STAs may communicate directly with each other (e.g., STA 110 may communicate with STA 112 without such communication being routed through an AP).

[0046] IEEE 802.11 devices (e.g. , IEEE 802.11 APs in a BSS) may use beacon frames to announce the existence of a WLAN network. An AP, such as AP 102, may transmit a beacon on a channel, e.g. , a fixed channel, such as a primary channel. A STA may use a channel, such as the primary channel, to establish a connection with an AP.

[0047] STA(s) and/or AP(s) may use a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) channel access mechanism. In CSMA/CA a STA and/or an AP may sense the primary channel. For example, if a STA has data to send, 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 at a given time, e.g. , in a given BSS. Channel access may include RTS and/or CTS signaling. For example, an exchange of a request to send (RTS) frame may be transmitted by a sending device and a clear to send (CTS) frame that 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 alert other STAs to hold off from accessing the medium while the AP initiating the RTS may transmit its data. On receiving the CTS frame from the STA, the AP may send the data to the STA.

[0048] A device may reserve spectrum via a network allocation vector (NAV) field. For example, in an IEEE 802.11 frame, the NAV field may be used to reserve a channel for a time period. A STA that wants to transmit data may set the NAV to the time for which it may expect to use the channel. When a STA sets the NAV, the NAV may be set for an associated WLAN or subset thereof (e.g., a BSS). Other STAs may count down the NAV to zero. When the counter reaches a value of zero, the NAV functionality may indicate to the other STA that the channel is now available.

[0049] The devices in a WLAN, such as an AP or STA, may include one or more of the following: a processor, a memory, a radio receiver and/or transmitter (e.g., which may be combined in a transceiver), one or more antennas (e.g. , antennas 106 in FIG. 1A), etc. A processor function may comprise one or more processors. For example, the processor may comprise 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), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The one or more processors may be integrated or not integrated with each other. The processor (e.g., the one or more processors or a subset thereof) may be integrated with one or more other functions (e.g. , other functions such as memory). The processor may perform signal coding, data processing, power control, input/output processing, modulation, demodulation, and/or any other functionality that may enable the device to operate in a wireless environment, such as the WLAN of FIG. 1A. The processor may be configured to execute processor executable code (e.g., instructions) including, for example, software and/or firmware instructions. For example, the processer may be configured to execute computer readable instructions included on one or more of the processor (e.g. , a chipset that includes memory and a processor) or memory. Execution of the instructions may cause the device to perform one or more of the functions described herein.

[0050] A device may include one or more antennas. The device may employ multiple input multiple output (MIMO) techniques. The one or more antennas may receive a radio signal. The processor may receive the radio signal, e.g. , via the one or more antennas. The one or more antennas may transmit a radio signal (e.g. , based on a signal sent from the processor).

[0051] The device may have a memory that 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. One or more memory units may be integrated with one or more other functions (e.g., other functions included in the device, such as the processor). The memory may include a 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 the processer. The processer may communicate with one or more entities of memory, e.g., via a system bus, directly, etc.

[0052] FIG. IB is a diagram of an example communications system 100 in which one or more disclosed features may be implemented. For example, a wireless network (e.g. , a wireless network comprising one or more components of the communications system 100) may be configured such that bearers that extend beyond the wireless network (e.g. , beyond a walled garden associated with the wireless network) may be assigned QoS characteristics.

[0053] 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 multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the

communications systems 100 may employ 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), single-carrier FDMA (SC-FDMA), and the like. [0054] As shown in FIG. IB, the communications system 100 may include at least one wireless transmit/receive unit (WTRU), such as a plurality of WTRUs, for instance 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, though it should be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and/or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d may be configured to transmit and/or receive wireless signals and may include user equipment (UE), a mobile station (e.g., a WLAN STA), a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, consumer electronics, and the like.

[0055] The communications systems 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 communication networks, such as the core network 106, the Internet 110, and/or the networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and/or network elements.

[0056] 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 the base station 114b may be configured to transmit and/or receive wireless signals within a particular geographic region, which may be referred to as a cell (not shown). The cell may further be 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 employ multiple-input multiple output (MIMO) technology and, therefore, may utilize multiple transceivers for each sector of the cell.

[0057] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an 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).

[0058] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c 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).

[0059] 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).

[0060] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 IX, 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), GSM EDGE (GERAN), and the like.

[0061] The base station 114b in FIG. IB may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, and the like. 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. IB, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the core network 106. [0062] The RAN 104 may be in communication with the core network 106, which may be any type of network configured to provide voice, data, applications, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. For example, the core network 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and/or perform high-level security functions, such as user authentication. Although not shown in FIG. IB, it should be appreciated that the RAN 104 and/or the core network 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may be utilizing an E-UTRA radio technology, the core network 106 may also be in communication with another RAN (not shown) employing a GSM radio technology.

[0063] 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 circuit-switched telephone networks that provide 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 the transmission control protocol (TCP), user datagram protocol (UDP) and the internet protocol (IP) in the TCP/IP internet protocol suite. The networks 112 may include wired or wireless communications networks owned and/or operated by other service providers. For example, the networks 112 may include another core network connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0064] 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. IB may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0065] FIG. 1C depicts an exemplary wireless transmit/receive unit, WTRU 102. A WTRU may be a user equipment (UE), a mobile station, a WLAN STA, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, consumer electronics, and the like. WTRU 102 may be used in one or more of the communications systems described herein. As shown in FIG. 1C, the 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 appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0066] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller,

Application Specific Integrated Circuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input/output processing, and/or any other functionality 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. 1C depicts the processor 118 and the transceiver 120 as separate components, it should be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0067] The transmit/receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the 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 IR, UV, or visible light signals, for example. In yet another embodiment, the transmit/receive element 122 may be configured to transmit and receive both RF and light signals. It should be appreciated that the transmit/receive element 122 may be configured to transmit and/or receive any combination of wireless signals.

[0068] In addition, although the transmit/receive element 122 is depicted in FIG. 1C as a single element, the WTRU 102 may include any number of transmit/receive elements 122. More specifically, the WTRU 102 may employ 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.

[0069] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit/receive element 122 and to demodulate the signals that are received by the transmit/receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, for example.

[0070] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128 (e.g. , a liquid crystal display (LCD) display unit or 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. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and/or the 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, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0071] The processor 118 may receive power from the power source 134, and may be configured to distribute and/or control the power to the other components in 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 cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0072] The processor 118 may also be coupled to the 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 in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g. , base stations 114a, 114b) and/or determine its location based on the timing of the signals being received from two or more nearby base stations. It should be appreciated that the WTRU 102 may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment.

[0073] 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 photographs or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, and the like.

[0074] Systems, methods, and instrumentalities are disclosed for SIG Design for OFDMA in WLAN Systems. RUs may be efficiently allocated and signaled in OFDMA WLAN to support IoT/MTC. RU allocation may be signaled in a HE SIG field. RU allocation may be signaled, for example, from a per RU perspective. RU allocation may be signaled per STA, for example, in support of distributed RU allocation, such as when RUs allocated to a STA may be distributed evenly across the entire band. RU scheduling information may be signaled per STA, for example, in support of contiguous RU allocation. RUs allocated to a STA may be physically adjacent (e.g. contiguous). RU allocation signaling may be uniform across the whole bandwidth, or frequency segment, for a bandwidth larger than 20MHz. The allowed RU allocation patterns may be limited, which may reduce the signaling complexity and overhead. An AP may announce a resource allocation in a resource allocation frame, or as a part of a previous transmission, such as a PPDU within an A-MDPU or A-MSDU. RU allocation signaling may support IoT. A minimum number of resources may be utilized for an IoT operation, such as the center 26 tones. A SIG field may be carried within a symmetrical RU allocation, for example, to reduce interference due to RF I/Q imbalance in OFDMA. Limitations may be applied to the RU allocation rules in OFDMA based WLAN system, e.g., to limit a system to symmetric RU allocation. Dynamic packing (e.g. padding) and associated signaling may improve efficiency and reduce signaling overhead.

[0075] A Wireless Local Area Network (WLAN) may have multiple modes of operation, such as an Infrastructure Basic Service Set (BSS) mode and an Independent BSS (IBSS) mode. A WLAN in Infrastructure BSS mode may have an Access Point (AP) for the BSS. One or more stations (STAs) may be associated with an AP. An AP may have access or an interface to a Distribution System (DS) or other type of wired/wireless network that carries traffic in and out of a BSS. Traffic to STAs that originates from outside a BSS may arrive through an AP, which may deliver the traffic to the STAs. Traffic originating from STAs to destinations outside a BSS may be sent to an AP, which may deliver the traffic to respective destinations. Traffic between STAs within a BSS may be sent through an AP, e.g., from a source STA to the AP and from the AP to the destination STA. Traffic between STAs within a BSS may be peer-to-peer traffic. Peer-to-peer traffic may be sent directly between the source and destination STAs, for example, with a direct link setup (DLS) using an 802. l ie DLS or an 802.1 lz tunneled DLS (TDLS). A WLAN in Independent BSS (IBSS) mode may not have an AP, and, STAs may communicate directly with each other. An IBSS mode of communication may be referred to as an "ad-hoc" mode of communication.

[0076] An AP may transmit a beacon on a fixed channel (e.g. a primary channel), for example, in an 802.1 lac infrastructure mode of operation. A channel may be, for example, 20 MHz wide. A channel may be an operating channel of a BSS. A channel may be used by STAs, for example, to establish a connection with an AP. A channel access mechanism in an 802.11 system is Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). A STA, including an AP, may sense a primary channel, for example, in a CSMA/CA mode of operation. A STA may back off, for example, when a channel is detected to be busy so that only one STA may transmit at a time in a given BSS.

[0077] High Throughput (HT) STAs may use, for example, a 40 MHz wide channel for communication, e.g., in 802.11η. A primary 20 MHz channel may be combined with an adjacent 20 MHz channel to form a 40 MHz wide contiguous channel.

[0078] Very High Throughput (VHT) STAs may support, for example, 20 MHz, 40 MHz, 80 MHz and 160 MHz wide channels, e.g. , in 802.1 lac. 40 MHz and 80 MHz channels may be formed, for example, by combining contiguous 20 MHz channels. A 160 MHz channel may be formed, for example, by combining eight contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. An 80+80 configuration may be passed through a segment parser that divides data into two streams, for example, after channel encoding. Inverse Fast Fourier Transform (IFFT) and time domain processing may be performed, for example, on each stream separately. Streams may be mapped onto two channels. Data may be transmitted on the two channels. A receiver may reverse the encoding process within a transmitter mechanism. A receiver may recombine data transmitted on multiple channels. Recombined data may be sent to Media Access Control (MAC).

[0079] Sub-GHz (e.g. MHz) modes of operation may be supported, for example, by 802.11af and 802.11 ah. Channel operating bandwidths and carriers may be reduced, for example, relative bandwidths and carriers used in 802.1 In and 802.1 lac. 802.1 laf may support, for example, 5 MHz, 10 MHz and 20 MHz bandwidths in a TV White Space (TVWS) spectrum. 802.11 ah may support, for example, 1 MHz, 2 MHz, 4 MHz, 8 MHz and 16 MHz bandwidths in non-TVWS spectrum. An example of a use case for 802.11 ah may be support for Meter Type Control (MTC) devices in a macro coverage area. MTC devices may have limited capabilities (e.g. limited bandwidths) and may be designed to have a very long battery life.

[0080] WLAN systems (e.g. 802.11η, 802.1 lac, 802.1 laf and 802.11ah systems) may support multiple channels and channel widths, such as a channel designated as a primary channel. A primary channel may, for example, have a bandwidth equal to the largest common operating bandwidth supported by STAs in a BSS. Bandwidth of a primary channel may be limited by a STA that supports the smallest bandwidth operating mode. In an example of 802.1 lah, a primary channel may be 1 MHz wide, for example, when there are one or more STAs (e.g. MTC type devices) that support a 1 MHz mode while an AP and other STAs support a 2 MHz, 4 MHz, 8 MHz, 16 MHz or other channel bandwidth operating modes. Carrier sensing and NAV settings may depend on the status of a primary channel. As an example, all available frequency bands may be considered busy and remain idle despite being available, for example, when a primary channel has a busy status due to a STA that supports a 1 MHz operating mode transmitting to an AP on the primary channel.

[0081] Available frequency bands may vary between different regions. As an example, in the United States, available frequency bands used by 802.1 lah may be 902 MHz to 928 MHz in the United States, 917.5 MHz to 923.5 MHz in Korea and 916.5 MHz to 927.5 MHz in Japan. Total bandwidth available may vary between different regions. As an example, the total bandwidth available for 802.1 lah may be 6 MHz to 26 MHz depending on the country code.

[0082] Spectral efficiency may be improved, for example, by downlink Multi-User Multiple- Input/Multiple-Output (MU-MIMO) transmission to multiple STAs in the same symbol's time frame, e.g., during a downlink OFDM symbol. Downlink MU-MIMO may be implemented, for example, in 802.1 lac and 802.1 lah. Interference of waveform transmissions to multiple STAs may be avoided, for example, when downlink MU-MIMO uses the same symbol timing to multiple STAs. Operating bandwidth of a MU-MIMO transmission may be limited to the smallest channel bandwidth supported by STAs in a MU-MIMO transmission with an AP, for example, when STAs involved in a MU-MIMO transmission with an AP use the same channel or band.

[0083] IEEE 802.11™ High Efficiency WLAN (HEW), which may be referred to as High Efficiency (HE), may enhance the quality of service (QoS) experienced by wireless users in many usage scenarios, such as high-density deployments of APs and STAs in 2.4 GHz and 5 GHz bands. HE WLAN Radio Resource Management (RRM) technologies may support a variety of applications or usage scenarios, such as data delivery for stadium events, high user density scenarios such as train stations or enterprise/retail environments, video delivery and wireless services for medical applications.

[0084] Short packets, which may be generated by network applications, may be applicable in a variety of applications, such as virtual office, TPC acknowledge (ACK), Video streaming ACK, device/controller (e.g. mice, keyboards, game controls), access (e.g. probe

request/response), network selection (e.g. probe requests, Access Network Query Protocol (ANQP)) and network management (e.g. control frames).

[0085] MU features, such as uplink (UL) and downlink (DL) Orthogonal Frequency- Division Multiple Access (OFDMA) and UL and DL MU-MIMO, may be implemented in WLAN. DL acknowledgments sent in response to UL MU transmissions may be multiplexed. [0086] OFDMA numerology for HEW may be provided. OFDMA building blocks may be, for example, 20 MHz, 40 MHz and 80 MHz.

[0087] FIG. 2 is an example of OFDMA numerology 200 for a 20 MHz building block. A 20 MHz OFDMA building block may be defined, for example, as 26-tone with 2 pilots, 52-tone with 4 pilots and 106-tone with 4 pilots. As an example, there may be 7 DC Nulls and (6,5) guard tones (e.g. , 6 guard tones on the left hand side and 5 guard tones on the right hand side), for example, at locations shown in FIG. 2. An OFDMA PPDU may carry a mix of different tone unit sizes within a 242 tone unit boundary.

[0088] FIG. 3 is an example of OFDMA numerology 300 for a 40 MHz building block. A 40 MHz OFDMA building block may be defined, for example, as 26-tone with 2 pilots, 52-tone with 4 pilots, 106-tone with 4 pilots and 242 -tone with 8 pilots. As an example, there may be 5 DC Nulls and (12,11) guard tones, for example, at locations shown in FIG. 3.

[0089] FIG. 4 is an example of OFDMA numerology 400 for an 80 MHz building block. An 80 MHz OFDMA building block may be defined, for example, as 26-tone with 2 pilots, 52-tone with 4 pilots, 106-tone with 4 pilots, 242-tone with 8 pilots and 484-tone with 16 pilots. As an example, there may be 7 DC Nulls and (12,11) guard tones, for example, at locations shown in FIG. 4.

[0090] One or more of a legacy Short Training Field (STF), a Long Training Field (LTF), and a Signal (SIG) Field may be provided. High Efficiency (HE) SIG-A and SIG-B design may be provided.

[0091] A HE PLCP (Physical Layer Convergence Protocol) protocol data unit (PPDU) may comprise a legacy (L) preamble (e.g. , L-STF, L-LTF and L-SIG), which may be duplicated on each 20 MHz block, for example, for backward compatibility with legacy devices.

[0092] A HE-SIG-A field may be duplicated on each 20 MHz block, for example, after the legacy preamble to indicate common control information. As an example, a HE-SIG-A field may be implemented using a Discrete Fourier Transform (DFT) period of 3.2 and subcarrier spacing of 312.5 kHz.

[0093] A HE-SIG-B field may be implemented, for example, using a DFT period of 3.2us and subcarrier spacing of 312.5kHz Resource Allocation in other Technologies.

[0094] A MAC header may include a Receive Address (RA) and/or a Destination Address (DA). An RA in a MAC header may indicate a MAC address of a next immediate STA on a wireless medium to receive a frame, for example, in single user 802.11. A DA may indicate a MAC address of a final destination to receive a frame. [0095] Resource allocation information may be placed in a physical layer (PHY) header (e.g. VHT-SIG-Al) as a Partial Association Identifier (AID) from a 48-bit BSSID and a 16-bit AID of STA(s), for example, in 802.1 lac. A Group ID may be signaled in VHT SIG-A, for example, so that it may be used by a STA to determine whether an MU PPDU is meant for it and to identify which space time streams to demodulate in a DL-MU-MIMO transmission. Assignment of STAs to groups may be managed by Group ID management frames.

[0096] Resource allocation may be more complicated in a BSS using OFDMA compared to an OFDM system. As an example, a BSS with 80 MHz bandwidth may have 37 RUs and may allocate numerous STAs at the same time. Efficient RU-allocation signaling may indicate allocated RUs and/or associated STAs, for example, to enable OFDMA operation in WLAN systems. A signaling scheme may be scalable among different system bandwidths, such as 20, 40, 80, 160, or 80 + 80 MHz.

[0097] Low-cost MTC and/or IoT type devices may be supported in HE WLAN. Low-cost MTC and/or IoT devices may use a narrow bandwidth (e.g. 5MHz). (RU allocation signaling and/or RU-based feedback may enable efficient operation of low-cost MTC and/or IoT devices.

[0098] RF I/Q imbalance in OFDMA may cause interference. In an OFDMA-based system, one or more frequency resources presented in the form of sub-channels may be assigned to different radio links that may be in uplink or downlink directions. A signal transmitted over a sub-channel allocated on one side of a channel relative to a central frequency may create interference on the other side of the channel as the image of the original signal due to RF I/Q amplitude and/or phase imbalances.

[0099] FIG. 5 is an example power spectrum density of a partially loaded OFDM signal with RF I/Q imbalance. FIG. 5 depicts an example with 256 subcarriers in a 20 MHz channel. A subchannel with subcarriers from 199 to 224 (shown as sub-channel (SC) A) may be loaded with data. RF I/Q imbalance may generate approximately 23dBr interference in the image of the subchannel with subcarriers from -119 to -224 (shown as SC B).

[0100] In single BSS scenarios, e.g. , in OFDMA DL, interference may not be significant, for example, because transmit (Tx) power on all sub-channels are the same as are Rx powers of those sub-channels at each STA. However, in OFDMA UL, interference at the image subchannel (e.g. SC B) may be significant, for example, when there is no power control or the power control is not accurate. A STA using sub-channel B may be further from the AP than a STA using channel A.

[0101] FIG. 6 is an example of Bit Error Rate (BER) performance for an interfered signal. FIG. 6 shows the example BER performance of a signal transmitted on sub-channel B suffering from interference due to transmission on sub-channel A with I/Q imbalance. The line designated dP may represent the power difference between sub-channels A and B. dP > 0 may indicate that a signal power on SC B is lower than a signal power on SC A. As shown in FIG. 6, there may be significant performance loss, for example, when power is not well controlled.

[0102] RU allocation, for example, in an uplink OFDMA scenario, may account for and/or compensate for the impact of I/Q imbalance. RU allocation signaling may be designed, for example, to prevent system impairment due to I/Q imbalance.

[0103] RUs may be efficiently allocated and/or signaled in an OFDMA-based Wireless Local Area Network (WLAN) to support Internet of Things (IoT) and MTC (Machine Type Communications).

[0104] HE WLAN or similar HE systems may be implemented in a variety of ways (e.g. techniques, implementations). Techniques may have a variety of subset (e.g. variant) techniques. Techniques and/or subsets may be combined and/or modified.

[0105] RU allocation may be signaled in a PLCP header. Examples for RU allocation signaling in HE SIG and/or legacy SIG may be provided.

[0106] In a first example, RU allocation may be signaled, for example, from a per RU perspective. Several RU allocation signaling techniques may be variants of signaling RU allocation from a per RU perspective.

[0107] RU allocation may be signaled for a 20 MHz bandwidth system. Signaling an RU allocation for a 20 MHz bandwidth may include one or more of the following.

[0108] STA ID in a resource allocation may be signaled or represented, for example, by AID/PAID or a pre-assigned group ID and STA position within the group. A group ID may be signaled, for example, in a SIG-A (e.g. , an IEEE 802.1 lac SIG-A). The SIG-A may be transmitted before the HE SIG-A and/or HE SIG-B. The SIG-A may be signaled in the HE SIG- A and/or HE SIG-B preamble. A group ID field may have N bits. A group may comprise up to K STAs. A (e.g. each) STA may have a corresponding STA position within a group.

[0109] RU allocation information may be signaled in an HE SIG-B or split between HE SIG- A and HE SIG-B. A RU allocation field may be used to carry RU allocation information. An allocated STA ID may be signaled for each minimum-size RU (e.g. 26 tones in 802.11 ax), for example, using a STA position within the group or AID/PAID. In some cases, not all RUs may be allocated. A pre-defined codeword (e.g. all zeros or all ones) may be used to present a case of "not allocated," for a RU that is not allocated to any STA in a BSS.

[0110] FIG. 7 is an example format of a RU allocation field 702. A RU allocation field 702 may use the format shown in FIG. 7, for example, when an allocated STA may use a different modulation and coding scheme (MCS) and may have different number of spatial streams on each allocated RU. The example RU allocation field 702 may include a STA ID 704, a MCS 706,

[0111] FIG. 8 is an example format of a RU allocation field 802. A RU allocation field 802 may use the format shown in FIG. 8, for example, when an allocated STA may be restricted to use the same MCS and may have the same number of spatial streams on all allocated RUs within a BSS. An order of an allocated STA info fields may be determined (e.g. , implicitly decided) based on one or more preceding fields of allocation of RUs. The example RU allocation field 802 may include a MCS 804 and/or a Nsts 806.

[0112] RU allocation may be signaled for a bandwidth larger than 20 MHz. A bandwidth larger than 20 MHz may be expressed as a multiple p of 20 MHz (e.g. p x 20 MHz). A 20 MHz RU allocation signaling may be extended, e.g. , linearly. The 20 MHz RU allocation signaling may be extended with one or more changes, for a bandwidth larger than 20 MHz. Such RU allocation signaling may include one or more of the following.

[0113] A STA ID in the resource allocation may be signaled or represented by AID/PAID or a pre-assigned group ID and a STA position within the group. Group management for bandwidths greater than 20 MHz OFDMA may be handled in multiple ways when a group ID is used. For example, one group may be used for all STAs to be allocated in the entire bandwidth. A single group ID may be signaled in a SIG-A (e.g., an IEEE 802.1 lac SIG-A) which may be transmitted in one or more of the following ways: before the HE SIG-A and HE SIG-B, in the HE SIG-A, and/or in HE SIG-B as a part of the preamble. As another example, one group may be used for each 20 MHz band within the entire bandwidth. There may be p group IDs to be signaled to the STAs. The p group IDs may be signaled, for example, sequentially in the order of associated 20 MHz bands in the HE SIG-A and/or HE SIG-B. The group ID of the first 20 MHz may be signaled first, followed by the group ID of the second 20 MHz and so on. In an example, a corresponding group ID of a 20 MHz bandwidth may be signaled in the HE SIG-B, for example, when a non-duplicated HE SIG-B is transmitted on each 20 MHz band.

[0114] A RU allocation field for a bandwidth larger than 20 MHz may be a linear extension of one or more 20MHz bandwidth RU allocation field formats. A STA ID subfield may add \log₂ ^p] bits to signal that a corresponding group ID among p group IDs is used for the entire bandwidth, for example, when one or more of the following conditions are true: a group ID and/or a STA position within a group may be used to represent the allocated STA ID; one common HE SIG-B may be used across an entire bandwidth or a common HE SIG-B may be duplicated on each 20 MHz band; or p group IDs may be used for the entire bandwidth (e.g. , one group for each 20 MHz band).

[0115] A numerical analysis for the 20, 40, and 80 MHz bands may provide the following estimate of the signaling overhead: for example, N bits (e.g. 6 bits as in 802.1 lac) for a Group ID index and Group size may allow up to 9 STAs. A 36 bit common RU allocation field may permit four bits to signal a STA position in a group having 9 RUs per 20 MHz band. Total overhead may be N + 36 bits for a 20 MHz band, N + (5*28) bits for 60 MHz and N + (6*37) bits for 80 MHz. A Group ID management frame may comprise 320 bits (e.g. 2^AN(group array )+2^ΛΝ*4 (position array )=320 bits ), 384 bits (e.g. 2^AN(group array )+2^ΛΝ*5 (position array) = 384 bits) or 448 bits (e.g. 2^AN(group array)+2^AN*6 (position array) = 448 bits), for example, to support groups allowing up to 9 STAs.

[0116] RU allocation may be signaled for downlink operation, for example, according to one or more of the following.

[0117] An AP may perform group management of two or more STAs that are capable of OFDMA-based transmission and reception using group management frames, for example, when group ID is used for STA ID in RU allocation signaling.

[0118] An AP may monitor conditions of a BSS (e.g. such as the amount of downlink data buffered at the AP, power savings/sleep cycle, etc.). An AP may determine to perform an OFDMA transmission, for example, when one or more of the conditions warrant an OFDMA transmission. As an example, several STAs may have enough downlink data buffered at the AP such that the amount of data would allow efficient OFDMA resource utilization.

[0119] An AP may choose one or more STAs for DL transmission. An AP may choose corresponding resource allocation and/or transmission parameters for the one or more STAs, such as allocated RUs, MCS, MIMO parameters, amount of data to be transmitted, etc. , for example, according to an appropriate scheduling algorithm.

[0120] An AP may perform downlink OFDMA transmission accordingly. The AP may set one or more RU allocation and/or DL transmission parameters in the PLCP header in the OFDMA transmission, for example, using RU allocation signaling described herein.

[0121] A STA may decode a detected PLCP header (e.g. legacy SIG, HE SIG-A, HE SIG-B) and may interpret a received PLCP header, e.g., according to a format specified in the RU allocation signaling described herein.

[0122] A STA may tune its receiver to allocated RU(s) to receive and decode its downlink data according to one or more parameters in received SIGs (e.g. legacy SIGs, HE SIG-A and SIG-B). [0123] FIG. 9 is an example of tone plans for a 20 MHz band and RU unit labels. A STA may determine one or more tone plans (e.g. including pilots and DC nulls) according to allocated RUs. As an example, a RU unit labeled as "Unit 10" in FIG. 9 may be allocated to a STA, for example, when received RU allocation signaling indicates that RU units 1 and 2 are allocated to the STA.

[0124] RU allocation signaling in the uplink may be provided, for example, according to one or more of the following.

[0125] An AP may perform group management of STAs that are capable of OFDMA-based transmission and reception using group management frames, for example, when group ID is used for STA ID in RU allocation signaling.

[0126] An AP may monitor conditions of a BSS (e.g. amount of uplink data buffered at the STAs, power savings/sleep cycle, path loss, or received power of individual STA at the AP). An AP may determine to perform an uplink OFDMA transmission, for example, when conditions warrant a transmission. As an example, several STAs may have enough uplink data, the amount of data may allow efficient OFDMA resource utilization, the several STAs have similar received power at the AP, etc.

[0127] An AP may choose one or more STAs for an UL transmission. An AP may choose corresponding resources allocation and/or transmission parameters for STAs, such as allocated RUs, MCS, MIMO parameters, amount of data to be transmitted, etc., for example, according to an appropriate scheduling algorithm.

[0128] An AP may trigger frame soliciting a transmission of UL MU PPDU from chosen STAs. An AP may set RU allocation and DL transmission parameters in the trigger frame using aforementioned RU allocation signaling.

[0129] A STA may interpret RU allocation signaling in a received trigger frame, for example, according to a format specified in aforementioned RU allocation signaling, e.g., upon receiving a valid trigger frame with RU allocation for it.

[0130] A STA may transmit UL MU PPDU according to RU allocation and transmission parameters received in a trigger frame as an immediate response to the Trigger frame.

[0131] A STA may determine tone plans (e.g. including pilots and DC nulls) according to allocated RUs. As an example, a RU unit labeled as Unit "10" in FIG. 9 may be allocated to a STA, for example, when received RU allocation signaling indicates that RU units 1 and 2 are allocated to the STA. [0132] RU allocation may be signaled per STA, for example, in support of distributed RU allocation, such as when RUs allocated to a STA may be distributed evenly across the entire band.

[0133] FIG. 10 is an example of distributed RU signaling with a fixed STA information size. A RU signaling field may be designed as shown in FIG. 10. There may be N STA Info fields 1010 (e.g. STA Info 1 to N). A 'k' (e.g. 1 through N) STA info field may carry RU scheduling and other information for a kth STA. A STA Info field may include one or more fields, such as a STA ID field 1012, a RU Starting Position field 1014, a RU Spacing field 1016, an MCS field 1018, and/or an Nsts field 1020.

[0134] A STA ID field 1012 may be used to cany STA identification. A STA ID may be, for example, a combination of a group ID and STA position within a group. As an example, a STA ID may indicate a STA in Group M with position L, e.g., [Group M, position L]. STA IDs within a signaling field may not be limited to a particular group. A STA ID may be, for example, a compressed version of association ID (AID) and BSSID. A STA ID may be, for example, a compressed version of AID. As an example, a BSSID or other type of BSS identity may be signaled in a common SIG field.

[0135] A RU Starting Position field 1014 may be used to indicate a position of a first RU assigned to a STA. The position may be signaled, for example, using a RU index over an entire channel or using a band index and a RU offset over that band. In an example with a total bandwidth of 80MHz, two bits may be utilized to indicate four 20Mhz sub-bands and k bits may be used to signal up to 2k RU offset positions, where each 20MHz sub-band may support up to 2k RUs.

[0136] A RU Spacing field 1016 may be used to indicate a separation (e.g. in units of RUs) between assigned RUs.

[0137] An MCS field 1018 may indicate an MCS assigned to a STA. An MCS may be assigned to RUs (e.g. all RUs) allocated to a STA.

[0138] An Nsts field 1020 may indicate a number of spatial time streams assigned to a STA.

[0139] RU scheduling may be distributed. FIG. 11 is an example of distributed RU scheduling. In the example shown in FIG. 11, the RUs under the dashed lines may be assigned to a STA. The distance between these RUs may be indicated as RU spacing.

[0140] RU allocation may be signaled for uplink and downlink operation, for example, according to uplink and downlink RU allocation signaling for uplink and downlink operation in the first example. [0141] A RU signaling field may be inserted into SIG-A field, SIG-B field or SIG-A/SIG-B field. A RU signaling field inserted into SIG-A/SIG-B field may be split into two parts, a first part to SIG-A field and a second part to SIG-B field.

[0142] A RU signaling field may be carried in a control frame transmitted before the

OFDMA transmission period. For example, a RU signaling field may be carried in a trigger frame, which may be used to initiate an uplink OFDMA transmission.

[0143] RU scheduling information may be signaled per STA, for example, in support of contiguous RU allocation. RUs allocated to a STA may be physically adjacent.

[0144] FIG. 12 is an example of contiguous RU signaling with fixed STA Info size. A RU signaling field may be designed, for example, as shown in FIG. 12. There may be N STA Info fields 1210 (e.g. STA Info 1 to N). A 'k' (e.g. 1 through N) STA info field 1210 may carry RU scheduling and other information for a k^th STA. A STA Info field 1210 may include one or more fields, such as a STA ID field 1212, a RU Starting Position field 1214, a number of RUs field

1216, an MCS field 1218, or an N_sts field 1220.

[0145] A STA ID field 1212 may be used to cany a STA's identification. A STA ID may be, for example, a combination of a group ID and STA position within a group. As an example, a STA ID may indicate a STA in Group M with position L, e.g., [Group M, position L]. STA IDs within a signaling field may not be limited to a particular group. A STA ID may be, for example, a compressed version of association ID (AID) and BSSID. A STA ID may be, for example, a compressed version of AID. As an example, a BSSID or other type of BSS identity may be signaled in a common SIG field.

[0146] A RU Starting Position field 1214 may be used to indicate a position of a first RU assigned to a STA. The position of the first RU assigned to the STA may be signaled, for example, using a RU index over an entire channel. The position of the first RU assigned to the STA may be signaled, for example, using a band index and a RU offset over that band. In an example with a total bandwidth of 80MHz, two bits may be utilized to indicate four 20Mhz sub- bands and k bits may be used to signal up to 2k RU offset positions, where each 20MHz sub- band may support up to 2k RUs.

[0147] A number of RUs field 1216 may be used to indicate the number of contiguous RUs assigned to a STA.

[0148] An MCS field 1218 may indicate an MCS assigned to a STA. The MCS may be assigned to one or more (e.g. , all) RUs allocated to a STA.

[0149] An Nsts field 1220 may indicate a number of spatial streams assigned to a STA. [0150] FIG. 13 is an example of contiguous RU scheduling. Two or more RUs may be contiguously allocated.

[0151] FIG. 14 is an example of contiguous RU allocation with multiple RU sets. A STA may be assigned a plurality of sets of RUs. A set of RUs may be considered to be contiguously allocated.

[0152] FIGS. 15A and 15B are examples of contiguous RU signaling field designs with variable STA Info size. STA Info fields 1510 may have different sizes, for example, when the number of RU sets assigned to STAs may vary. The number of RU sets assigned to STAs may, for example, be signaled in another signaling field, which may be transmitted before the RU signaling field. As another example, a STA delimiter may be prepended to each STA Info field, such that STAs may detect the delimiter and the start of the STA Info field. A STA delimiter may be a predetermined sequence or agreed to (e.g. ad hoc) by a transmitter and receiver. A CRC protection may be applied to a STA delimiter.

[0153] FIG. 15A shows a signaling field design with per STA MCS assignment. A RU signaling field may be designed, for example, as shown in FIGS. 15A or 15B. There may be N STA Info fields (e.g. STA Info 1 to N). A 'k' (e.g. 1 through N) STA info field may carry RU scheduling and other information for a kth STA. A STA info field may comprise one or more of the following: a STA delimiter field 1512, a STA ID field 1514, one or more RU set fields 1520, an MCS field 1522, or an N_sts field 1524.

[0154] A STA delimiter field 1512 may be provided. A STA delimiter field 1512 may be optional, for example, when the size of each STA Info field 1510 is signaled in a SIG field before a RU signaling field.

[0155] A STA ID field 1514 may be used to cany STA identification. A STA ID may be, for example, a combination of a group ID and a STA position within a group. As an example, a STA ID may indicate a STA in Group M with position L, e.g. , [Group M, position L]. STA IDs within a signaling field may not be limited to a particular group. A STA ID may be, for example, a compressed version of association ID (AID) and BSSID. A STA ID may be, for example, a compressed version of AID. As an example, a BSSID or other type of BSS identity may be signaled in a common SIG field.

[0156] RU set fields 1520 (e.g. RU Set 1 to RU Set k) may be used to indicate a contiguous RU set allocation. A RU set field 1520 may comprise a RU starting position field 1526 and/or a number of RUs field 1528. The RU starting position field 1526 may be used to indicate the position of the first RU assigned to the STA. The number of RUs field 1528 may be used to indicate the number of contiguous RUs assigned to the STA. [0157] A MCS field 1522 may indicate an MCS assigned to a STA. A MCS may be assigned to one or more (e.g. , all) RUs allocated to a STA.

[0158] A Nsts field 1524 may indicate a number of spatial time streams assigned to a STA.

[0159] FIG. 15B shows a signaling field design with per RU set MCS assignment. For example, the one or more RU set information fields 1520 may include a MCS field 1532 and/or a N_sts field 1534.

[0160] RU allocation may be signaled for uplink and downlink operation, for example, according to uplink and downlink RU allocation signaling for uplink and/or downlink operation as described herein.

[0161] A RU signaling field may be inserted into a SIG-A field, a SIG-B field, or a SIG- A/SIG-B field. A RU signaling field inserted into a SIG-A/SIG-B field may be split into two parts, a first part to SIG-A field and a second part to SIG-B field.

[0162] A RU signaling field may be carried in a control frame transmitted before OFDMA transmission. For example, the RU signaling field may be carried in a trigger frame. The trigger frame may be used to initiate an uplink OFDMA transmission.

[0163] RU allocation may include a flat RU allocation signaling for a bandwidth larger than 20MHz, such as 40MHz, 80MHz, and/or 160 (or 80 + 80) MHz. Compared to the first example comprising a 20MHz-based hierarchical RU allocation for a bandwidth larger than 20MHz, a flat RU allocation across the whole bandwidth or frequency segment (e.g. for 160 (80+80) MHz) larger than 20MHz may be used to signal an RU allocation.

[0164] FIG. 16 is an example flat RU allocation signaling.

[0165] A STA ID in a resource allocation may be signaled or represented, for example, by AID/PAID. The STA ID in a resource allocation or a pre-assigned group ID and STA position within the group. One group may be used for one or more (e.g. , all) STAs to be allocated in an entire bandwidth, for example, when a group ID is used with a flat RU allocation across an entire bandwidth greater than 20 MHz. In a preamble, a group ID (e.g., an IEEE 802.1 lac group ID) may be signaled prior to a HE SIG-A and HE SIG-B. A group ID field may have N bits, each group may comprise up to K STAs and each STA may have a corresponding STA position within a group. As an example, reusing an 802.1 lac group ID field with N=6 bit and K=4, 5 and 6 bits may support up to 9, 18 and 37 STAs within a group for 20MHz, 40MHz and 80MHz, respectively.

[0166] RU allocation information may be signaled. RU allocation information may be signaled in an HE SIG-A, HE SIG-B or split between HE SIG-A and HE SIG-B. RU scheduling information may be signaled per STA by one or any combination of the following three examples and/or other implementations.

[0167] A 1-dimension (ID) minimum RU M-bitmap (ID min RU bitmap) may be used to signal RU allocation for each STA, where M may represent the total number of minimum-size RUs for a given bandwidth (or frequency segment). As an example, 9-bitmap, 18-bitmap and 37-bitmap may be used to signal a RU allocation for each STA for 20MHz, 40MHz and 80MHz (or 160(80+80) MHz), respectively. A bit in a bitmap may be binary (e.g. , 1 or 0), for example, to indicate whether a corresponding minimum-size (minimized) RU is allocated to a STA. For example, 1 may denote an allocation of a minimized RU to a STA while 0 may denote no allocation to a STA. A 37-bitmap may be used to signal RU allocation for 80MHz. As an example, the first and the 37th bits in the bitmap equal to 1 may indicate the first and the last (i.e. 37th) 26tone-RU are allocated to the STA.

[0168] A RU-size associated with a bitmap RU allocation may be signaled (e.g., explicitly signaled) to a STA for demodulation and decoding. In an example, a three bit (3 bit) RU Size Indication (e.g. RU Size Indication) may indicate six different RU-sizes, such as 26-tone RU, 52- tone RU, 106-tone RU, 242-tone RU, 484-tone RU and 996-tone RU. Mapping between six kinds of RU size and a 3-bit size indication may be predefined or specified in any format. A number of (e.g. T) 3 -bit RU Size Indication may be signaled, for example, depending on the total number of (e.g. T) RUs allocated to a STA. T 3-bit RU Size Indication may be signaled, for example, after ID min RU bitmap.

[0169] A RU-size associated with a bitmap RU allocation may be signaled (e.g. , implicitly signaled) to a STA for demodulation and decoding, for example, when it may be pre-defined or assumed that a single "1" bit denotes a RU allocation larger than minimum size RU (e.g. 26tone- RU size). As an example of a 37-bitmap used to signal RU allocation for 80MHz, first and 2nd bits of the bitmap equal to 1 may signal the first 52tone-RU is allocated to the STA. Implicit signaling of different RU sizes may be used to allocate different-size RU across the entire band.

[0170] As an example of a 37-bitmap used to signal RU allocation for 80MHz, e.g., as shown in FIG. 16, first, 2nd, 3rd, 4th and 5th bits of the bitmap equal to 1 may signal two 52- tone RUs or one 106-tone RU plus one 26-tone RU (the 5th bit) are allocated to the STA. In an example, only the 5th 26-tone may be allocated, for example, because 52-tone and 106-tone RUs cannot be allocated to the 5th 26-tone location as indicated in the example shown in FIG. 16.

[0171] L bits may be used to signal a configurable RU allocation across an entire bandwidth (or frequency segment). L may be subject to the total number of configurable RU allocation across the whole bandwidth (or frequency segment), e.g. , 2^L >= total number of configurable RU allocation across an entire bandwidth (or frequency segment). As an example for 20MHz, 40MHz and 80MHz there may be, for example, 16, 33 and 68 configurable RU allocations, where L equal to 4, 6 and 7 bits may be used, respectively, to signal the allocation of the configurable RU to the STA. Mapping between configurable RU location and L-bit indication may be predefined and/or specified in any format. L bits may signal which configurable RU is allocated to a STA, for example, when each STA is allocated to one RU. The total number of RUs allocated to a STA (e.g. T RUs) may be signaled, for example, when more than one RU may be allocated to one STA. RU allocation signaling may be followed by T L-bit Indexes of RU allocation.

[0172] A 2-dimension (2-D) RU bitmap may signal the location of RU allocation across an entire bandwidth (or frequency segment). A first dimension of a 2D RU bitmap may signal RU- size, which may correspond to a row of RU building blocks, e.g. , as shown in FIG. 16. Row 1, 2, 3, 4, 5 and 6 may indicate 26-tone RU, 52-tone RU, 106-tone RU, 242-tone RU, 484-tone RU, and 996-tone RU, respectively. A second dimension of a 2D RU bitmap may signal an index of RUs for a given row or RU-size allocated to a desired STA. A different size of ID bitmap may be used for a different RU-size. As an example, a 2D size may be [1, 37], [2,16], [3,8], [4,4], [5,2], and/or [6,1]. One or more ID RU bitmaps may be signaled for RU allocation for a STA, for example, depending on bandwidth. As an example, 4, 5, and 6 2D RU bitmaps may be signaled, for example, for 20MHz, 40MHz, and 80MHz, respectively.

[0173] A RU signaling field may be used to carry one or more of the following RU allocation information.

[0174] A STA Info k field may carry RU scheduling and/or other information for a kth STA. A STA Info field may comprise, for example, one or more of a STA delimiter, a STA ID, and/or one or more RU allocation fields.

[0175] A STA delimiter may be prepended to each STA Info field, for example, to permit STAs to detect the delimiter and/or the start of the STA Info field. A STA delimiter may be a specified sequence or agreed to (e.g. ad hoc) by the transmitter and receiver. A CRC protection may be applied to a STA delimiter. The STA delimiter fields may have different sizes, for example, when the numbers of RUs assigned to STAs may be different. A STA delimiter field may be optional, for example, when the size of a STA Info field may be signaled in a SIG field before a RU signaling field.

[0176] A STA ID field may be used to carry STA identification information. STA ID information may include, for example, an AID/PAID or a pre-assigned group ID and STA position within the group. [0177] One or more RU allocation fields may be used to indicate one or more RUs allocated to a STA. A RU field may include one or more of the following sub-fields, for example, depending on the RU allocation implementation.

[0178] FIGS. 17A and 17B are examples of flat RU signaling. A ID min RU Bitmap field 1716 may be used to signal RU allocation for each STA. A ID min RU Bitmap may be, for example, 9-bitmap, 18-bitmap and 37 bitmap for 20MHz, 40MHz and 80MHz (or 160 (80+80) MHz), respectively. A bit in a bitmap may be binary (e.g., 1 or 0) to indicate whether a corresponding minimal-size RU is allocated to a STA.

[0179] A RU Size Ind field 1720 may be, for example, 3 bits to indicate one of six different RU-sizes, such as 26-tone RU, 52-tone RU, 106-tone RU, 242-tone RU, 484-tone RU and 996- tone RU.

[0180] FIG. 17A shows an example of RU signaling with one (e.g., a common) MCS field 1722 and N_sts field 1724 for each RU allocated to a STA. For example, each STA Info field 1710 may include one MCS field 1722 and one N_sts field 1724 for the STA. FIG. 17B shows an example of RU signaling with per-RU MCS and Nsts assignment where different RUs with different RU sizes may carry their own MCS and Nsts. Each STA Info field 1710 may include a plurality of MCS fields 1722 and/or a plurality of N_sts fields 1724. For example, each STA Info field 1710 may include a plurality of RU Size Ind fields 1720. Each of the plurality of RU size Ind fields 1720 may include a MCS field 1722 and/or aN_sts field 1724.

[0181] FIGS. 18A and 18B are examples of flat RU signaling. Each STA Info field 1810 may include a Total number of RU field 1816 and/or one or more Index of RU fields 1820. The total number of RU field 1816 may indicate a number of RUs allocated to a STA. The one or more Index of RU fields 1820 may indicate an index of a RU with the length of L bits. As an example, L= 4, 6, and 7 bits may represent 16, 33, and 68 RU allocations, respectively, for 20MHz, 40MHz, and 80MHz.

[0182] FIG. 18A shows an example of RU signaling with one (e.g., a common) MCS field 1822 and Nsts field 1824 for all RUs allocated to a STA. For example, each STA Info field 1810 may include one MCS field 1822 and one N_sts field 1824 for the STA. FIG. 18B shows an example of RU signaling with per-RU MCS and Nsts assignment where different RUs with different RU size may carry their own MCS and Nsts. Each STA Info field 1810 may include a plurality of MCS fields 1822 and/or a plurality of N_sts fields 1824. For example, each STA Info field 1810 may include a plurality of Index of RU fields 1820. Each of the plurality of Index of RU fields 1820 may include a MCS field 1822 and/or a N_sts field 1824. [0183] FIGS. 19A and 19B are examples of flat RU signaling. Each STA Info field 1910 may include a plurality of 2D RU Bitmap fields 1920. A 2D RU Bitmap field 1920 may signal, for example depending on bandwidth, six 2D RU Bitmaps with different sizes (e.g. [1, 37],

[2,16], [3,8], [4,4], [5,2] and [6,1]), e.g., to indicate RU allocation to a STA.

[0184] FIG. 19A shows an example of RU signaling with one (e.g., a common) MCS field 1922 and Nsts field 1924 for each RU allocated to a STA. For example, each STA Info field 1910 may include one MCS field 1922 and one Nsts field 1924 for the STA. FIG. 19B shows an example of RU signaling with per-RU MCS and Nsts assignment where different RUs with different RU size may carry their own MCS and Nsts. Each STA Info field 1910 may include a plurality of MCS fields 1922 and/or a plurality of N_sts fields 1924. For example, each STA Info field 1910 may include a plurality of 2D RU Bitmap fields 1920. Each of the plurality of 2D RU Bitmap fields 1920 may include a MCS field 1922 and/or a N_sts field 1924.

[0185] An MCS field 1922 may indicate an MCS assigned to a STA. The same or different MCS may be assigned to all RUs allocated to a STA.

[0186] An N_sts field 1924 may indicate a number of spatial time streams assigned to a STA. The number of spatial time streams may be the same or different for each RU allocated to a STA.

[0187] Flat RU allocation signaling may support flexible scheduling, such as support for any contiguous or non-contiguous RU allocation to any STA over any bandwidth (or frequency segment), including when not all RUs are allocated for an entire bandwidth (or frequency segment). Flat allocation signaling may be applicable to any bandwidth, e.g. , larger, smaller or equal to 20MHz.

[0188] RU allocation may be signaled for uplink and downlink operation, for example, according to uplink and downlink RU allocation signaling for uplink and downlink operation as described herein.

[0189] One or more RU allocation patterns may be restricted, which may reduce the signaling complexity and/or overhead. As an example, in a 20 MHz band, RU allocation patterns may be limited (e.g., to the RU allocation patterns shown in FIG. 20).

[0190] FIG. 20 is an example of limited RU allocations for a 20 MHz band. Larger bandwidths, e.g. , contiguous bandwidths > 40 MHz, such as 60 and 80 MHz, may comprise an extra 26-tone RU relative to example RU allocation patterns shown in FIG. 20.

[0191] Type 1 signaling may be disclosed. RU allocation may be signaled per STA. In an example, each STA may be allocated a unit (e.g., 1 to 16) in a 20 MHz band. A STA ID and a

RU Unit index may be sent to assign a resource to a STA. [0192] A STA ID in a resource allocation may be signaled or represented by AID/PAID. The STA ID in a resource allocation may be signaled or represented by a pre-assigned group ID and STA position within the group. A group ID may be signaled in a legacy 802.1 lac SIG-A (e.g., which may be transmitted ahead of HE SIG-A and/or HE SIG-B), in an HE SIG-A preamble, or in an HE SIG-B preamble. A group ID field may have N bits. A group may include up to K STAs. A STA may have a corresponding STA position within the group.

[0193] RU allocation information may be signaled. RU allocation information may be signaled in an HE SIG-B. RU allocation information may be split between HE SIG-A and HE SIG-B. A RU allocation field may be used to carry RU allocation information, for example, such as a RU Unit index (e.g. 1 to 16 may be indicated by 4 bits).

[0194] Signaling overhead may be calculated, for example, as the number of allocated STAs * (STA ID + 4). In an example, a maximum overhead may be 9 * (STA ID + 4).

[0195] FIG. 21 is an example of type 1 signaling that explicitly signals a number of STAs.

[0196] FIG. 22 is an example of type 1 signaling that explicitly signals a number of STAs.

[0197] In an example, the number of STAs in an allocation may be signaled and the STA ID and RU allocation fields may be signaled, for example, after the number of STAs. In an example, a delimiter, e.g. [0000], may be placed after STA IDs, e.g., to indicate the total number of STAs allocated.

[0198] Type 2 signaling may be disclosed. A bitmap of allocated RU units (e.g. , 16 bits) may be sent, for example, to indicate the resources that are allocated. The number of STAs in the allocation may be implicitly signaled. STA ID may be sent, for example, in the order of the positive bitmap. In an example, a separate bitmap may be sent for each of the number of STAs to indicate the resources allocated. In an example, a single bitmap may be sent for the number of (e.g. , all) STAs to indicate the specific allocation. When a single bitmap is sent to indicate the allocation of the number of STAs, the STAID order implicitly maps to the allocated resource. A single STA may have multiple allocations. A STA ID in a resource allocation may be signaled or represented by an AID/PAID. A STA ID in a resource allocation may be signaled or represented by a pre-assigned group ID and STA position within the group. . RU allocation information may be signaled in an HE SIG-B. RU allocation information may be split between HE SIG-A and HE SIG-B. A RU allocation field may be used to carry RU allocation information, for example, such as a RU Unit index.

[0199] Signaling overhead may be calculated, for example, as a number of allocated STAs *

STA ID + 16. In an example, a maximum overhead may be 9 * STA ID + 16.

[0200] FIG. 23 is an example of type 2 signaling that implicitly signals a number of STAs. [0201] FIG. 24 is an example of type 2 signaling that implicitly signals a number of STAs.

[0202] FIG. 25 is an example of type 2 signaling that implicitly signals a number of STAs.

[0203] In an example scenario, [1, 2, 5, 11, 15] may be allocated and STA ID may be 6 bits. Type 1 signaling may comprise 50 bits while type 2 signaling may comprise 46 bits.

[0204] Overhead may be reduced, for example, when the AP and STA agree on a minimum allowable and/or a limited number of allowable bandwidths (e.g. only one bandwidth). A 26 RU channel at DC or between 20 MHz bands (such as channel 5) may be (e.g. always) allocated.

[0205] FIG. 26 is an example of a minimum allowable bandwidth. In an example, three bit signaling may be provided where a minimum allowable bandwidth is 52 tones and allocation is based on RUs with index [5, 10, 11, 12, 13, 14, 15, 16].

[0206] FIG. 27 is an example of a limited number of allowable bandwidths. In an example, two bit signaling may be provided when the only allowable bandwidth is 104 tones and the allocation is based on [5, 14, 15].

[0207] A resulting bitmap may be used with the Type 1 and Type 2 RA signaling discussed above.

[0208] RU allocation may be signaled for uplink and downlink operation, for example, according to uplink and downlink RU allocation signaling for uplink and downlink operation as described herein.

[0209] An AP may announce resource allocation in a resource allocation frame. An AP may announce resource allocation as a part of a previous transmission, such as a PPDU within an A- MDPU or A-MSDU. An allocated resource may be associated with an index. A preamble, such as SIG-A or SIG-B of the resources, may comprise an index. The index may indicate resources allocated to STAs.

[0210] FIG. 28 is an example of a resource allocation frame format.

[0211] A resource allocation frame may include one or more of a PLCP header 2802, a MAC header 2804, one or more session information fields 2806, or a FCS field 2808.

[0212] A PLCP header 2802 may include information indicating that the frame is a resource allocation frame.

[0213] A MAC header 2804 may include information indicating that the frame is a resource allocation frame (e.g. Type or Subtype).

[0214] A session information field 2806 may include information about one or more sessions (e.g. , from session 1 to session N). The resource allocation frame may include a plurality of session information fields 2806. For example, each session may have a corresponding session information field 2806. A session information field may include one or more of the following information items regarding a session, during which an AP or one or more STAs may transmit UL and/or DL traffic. One or more of the following may apply.

[0215] A session number field 2810 may identify a session within a certain period of time, such as within the same TXOP or within a number of time units, such as milliseconds (ms).

[0216] A timing offset field 2812 may identify an offset for the starting of a session. An offset may be defined from a transmission of a current frame or a certain time reference.

[0217] A session type field 2814 may be, for example, UL, DL, UL/DL, random access, content based or a combination thereof.

[0218] A duration field 2816 may specify an approximate duration of a session.

[0219] A group ID field 2818 may identify a group of STAs that are involved in a session.

[0220] A number of allocation field 2820 may be included in the session information field 2806. The number of allocation field 2820 may indicate how many allocations are provided for the session.

[0221] One or more allocation fields 2822 may be included in the session information field 2806. Each of the one or more allocation fields 2822 may include information allocated to one or more STAs, such as an index field 2824, a STA info field 2826, and/or a resources field 2828. One or more of the following may apply. An index field 2824 may be used to identify one or more resources allocated to one or more STAs. A STA Info field 2826 may identify one or more STAs, e.g. , by STA MAC addresses, AID, and/or other identifiers. A resources field 2828 may indicate one or more resources allocated to one or more STAs identified in the STA Info field 2826. As an example, the one or more resources may be identified by a bit map. A "1" indicated in a bitmap may be associated with a Resource Block (RB) allocated to one or more STA(s). The size of a bitmap may be specified by bandwidth. A resources field 2828 may include an indication of the size of an RB. Resources may be identified by numbers associated with RBs.

[0222] A set or a subset of a portion of a resource allocation frame may be implemented as part of an information element, Action frames, NDP frames, Control, Management, Data or Extension frames, MAC or PLCP headers, etc.

[0223] An AP may announce resource allocation for one or more sessions (e.g. forthcoming sessions in the near future), for example, using a resource allocation frame, as a part of other frames, as part of a TXOP, as a part of an A-MPDU, as a part of a M-DSDU frame, and/or as a part of a trigger frame. A resource allocation may be associated with one or more of a Session Number, a Group ID, or an Index. [0224] FIG. 29 is an example of parameters announced by a resource allocation frame to indicate resource allocation in future sessions. FIG. 29 illustrates an example of how parameters announced in a resource allocation frame may be included in transmissions in future sessions.

[0225] A session number may, for example, be included in a common part of one or more transmissions in a session, for example, in SIG-A of UL and/or DL transmissions of STAs.

[0226] A Group ID may, for example, be included in a common part of one or more transmissions in a session, for example, in SIG-A of UL and/or DL transmissions of STAs allocated in the session, such as when a group of STA has been allocated with all the resources of a particular channel. Group ID may be included in a SIG-B (e.g. in a SIG-B associated with RBs allocated to a group of STAs), for example, when a group of STAs is allocated to part of the channel.

[0227] An index may, for example, be included in a part of one or more transmissions in a session, e.g. , in SIG-B associated with RBs allocated to one or more STAs identified in a resource allocation frame.

[0228] An AP may not include any extra indication in DL transmissions in the preambles for resource allocation. For example, an AP may not include an extra indication in a DL transmission preamble when the AP has announced resource allocation using a resource allocation frame.

[0229] A STA may wake up at a time determined by a timing offset. The timing offset may be associated with a session during which the STA has been allocated resources, for example, when the STA has received a resource allocation frame. When awake, a STA may search for an appropriate Group ID and/or an Index in preambles, such as SIG-A and SIG-B, for example, to find appropriate resources allocated to itself, e.g., by receiving DL transmissions from the AP. An Index and/or a Group ID may identify more than one STA. An identified STA may decode the remainder of a transmission, such as a MAC header, for example, to identify whether the resource is allocated to itself or whether the resource is allocated as a group transmission.

[0230] An AP may include one or more of a Session Number, a Group ID, or an Index in a trigger frame, e.g., in UL cases. A STA may receive a trigger frame and the STA may search for resources allocated to the STA in the UL session. A STA may transmit one or more UL transmissions to the AP according to the identified resources. A STA may include resource allocation information, e.g. , in the SIG-A and/or SIG-B parts or other parts of the preambles. Resource allocation information may include one or more of a Session Number, a Group ID, or an Index, in UL transmissions. [0231] IRU allocation signaling may support IoT. Low cost MTC may be enabled, for example, by low cost and/or efficient technology for allocation and/or scheduling of resources for MTC type devices. As an example, an IoT device may not require a large number of resources and/or bandwidth for an IoT operation. A minimum number of resources may be utilized for an IoT operation. For example, an IoT operation may use the center 26 tones.

[0232] FIG. 30 is an example narrow band allocation for IoT operation.

[0233] In an example, a radio may support operation over only 2.5 MHz of spectrum for data operations. Backward compatibility may be enabled, for example, by sending preamble and signaling fields over 20 MHz of bandwidth. A HE PPDU may not include legacy preambles (e.g. L-STF, L-LTF and L-SIG), for example, in narrow bandwidth (<20MHz) uplink transmissions using UL-OFDMA, such as the presented IoT example.

[0234] SIG-B may be used to indicate narrow band operation, such as for UL-OFDMA. One or more of the following may be indicated for narrowband data transmissions a control power, a transmission power, control of a number of pilots sent, control of a location of pilots sent, an indication to other STAs that narrow band operation is ongoing, or an indication of MCSs that may be supported.

[0235] A SIG may have a symmetric RU allocation. A symmetric RU allocation may, for example, reduce interference due to RF I/Q imbalance in OFDMA. One or more limitations may be applied to RU allocation rules in OFDMA based WLAN system. As an example, a system may be limited to symmetric RU allocation.

[0236] FIG. 31 is an example of a symmetric RU allocation. For example, as shown in FIG. 31, a first RU (e.g. , RU1) may be paired with a last RU (e.g. , RU 9) for symmetry. Symmetric RU pairs 1 (e.g., SRU1) may indicate a symmetric pairing of RU1 and RU9, e.g., SRU1 = [RU1, RU9]. Similarly, SRU2 may indicated a symmetric pairing of RU2 and RU8 (e.g. , [RU2, RU8]), SRU3 may indicate a symmetric pairing of RU3 and RU7 (e.g. , [RU3, RU7]), and SRU4 may indicate a symmetric pairing of RU4 and RU6 (e.g. , [RU4, RU6]).

[0237] A common signaling field, e.g. , HE-SIG-A or HE-SIG-B field, may use one or more bits to indicate a symmetric RU allocation. SRU indices (e.g. as an alternative to RU indices) may be utilized, for example, in the detailed RU allocation signaling part, e.g., to reduce signaling overhead.

[0238] A RU allocation signaling field may be carried in a control frame before the OFDMA transmission, e.g., a trigger frame. Symmetric RU allocation may be signaled in the control frame before the OFDMA transmission. One or more SRU indices may be utilized for RU allocation signaling. [0239] Paired RUs may be assigned to the same STA. RU information on an SRU may represent those on two paired RUs. Disclosed technology may be applied to or with symmetric RU allocation techniques, for example, by using SRU indices in place of RU indices. Symmetric RU allocation may mitigate an interference effect of RF I/Q imbalance.

[0240] Dynamic packing and associated signaling may be provided. Dynamic packing may improve efficiency and/or reduce signaling overhead.

[0241] A plurality of OFDM symbols may be sent via a MAC PDU. Each of the plurality of OFDM symbols may be associated with a first duration and/or a first length of data. The first duration may be associated with a number of modulated symbols assigned to the STA within an OFDM symbol of the plurality of OFDM symbols. The first length of data may be associated with a length (e.g., a maximum length) of data which can be carried in each of the plurality of OFDM symbols by the STA. Data may be mapped to the plurality of OFDM symbols.

[0242] A system may support one or more last OFDM symbol formats. The last OFDM symbol format may, for example, be based on the size of modulated data symbols left for the last OFDM symbol and/or the length of data to be transmitted in the last OFDM symbol (e.g. , the second length of data).

[0243] In a first format (e.g. , Format 1), a last OFDM symbol of the plurality of OFDM symbols may have a duration of 3.2 us excluding GI, for example, when the size of modulated symbols and/or the second length of data for the last OFDM symbol is equal or less than ¼ of the first length of data.

[0244] In a second format (e.g. Format 2), a last OFDM symbol of the plurality of OFDM symbols may have a duration of 6.4 us excluding GI, for example, when the size of modulated symbols and/or the second length of data for the last OFDM symbol is equal or less than ½ of the first length of data but greater than ¼ the first length of data.

[0245] In a third format (e.g. Format 3), a last OFDM symbol of the plurality of OFDM symbols may have a duration of 9.6 us excluding GI, for example, when the size of modulated symbols and/or the second length of data for the last OFDM symbol is equal or less than ¾ of the first length of data but greater than ½ of the first length of data.

[0246] In a fourth format (e.g. Format 4), a last OFDM symbol of the plurality of OFDM symbols may have a duration of 12.8 us excluding GI, for example, when the size of modulated symbols and/or the second length of data for the last OFDM symbol is greater than 3/4 of the first length of data. [0247] The first length of data may be the number of modulated symbols assigned to the STA by one OFDM symbol. When GI is taken into account, the last symbol duration may be [3.2, 6.4, 9.6, 12.8]+GI us, where GI may be 0.8us, 1.6us or 3.2us.

[0248] A second length of data, e.g. , a data length to be transmitted in the last OFDM symbol may be determined. For example, it may be determined that the second length of data to be transmitted in the last OFDM symbol is less than the first length of data. The last OFDM symbol may be associated with a transmission duration, e.g. , a first duration. For example, a transmitter may measure the length of data to be transmitted in the last symbol. The data length to be transmitted in the last OFDM symbol (e.g., the second length) may be compared to the length of available data carriers in the last OFDM symbol (e.g. , the first length). The second length may be determined to be less than the first length. The last OFDM symbol may be modified based on the second length (e.g. , such as using a ratio of the second length to the first length). For example, the last OFDM symbols may be modified to ¼, ½, or ¾ of the first duration depending on the second length. For example, the last OFDM symbol may be modified to ¼ of the first duration when the second length of data in the last OFDM symbol is less than or equal to ¼ of the first length of data. As another example, the last OFDM symbol may be modified to ½ of the first duration when the second length of data is less than or equal to ½ of the first length of data but greater than ¼ of the first length of data. As another example, the last OFDM symbol may be modified to ¾ of the first duration when the second length of data is less than or equal to ¾ of the first length of data but greater than ½ of the first length of data. As another example, the last OFDM symbol may not be modified when the second length of data is greater than ¾ of the first length of data. The second duration of the last OFDM symbol may be indicated via a PHY header or a MAC header. In another example, the ratio of the second length of data to the first length of data may be indicated via a PHY header or a MAC header.

[0249] A subcarrier mapping may be changed to enable the creation of a periodic symbol and one period of the periodic symbol may be transmitted, for example, when the amount of data is less than ¼ or ½ the length of the symbol (e.g. 64 symbols or 128 symbols using an 802.1 lax numerology if 20MHz channel is assigned to the STA). The periodic symbol may be created based on the second length of the last OFDM symbol.

[0250] A receiver may determine the length of the last OFDM symbol in a variety of ways. As an example, the length of the last OFDM symbol may be signaled, for example, in a PHY or MAC header. As an example, a receiver may estimate (e.g. blindly) the length of the last OFDM symbol, for example, based on (e.g. four) distinct length possibilities for the last OFDM symbol, e.g. ¼, ½, ¾, and 1 OFDM symbol. As an example, a length field in L-SIG may be reinterpreted to indicate the fragment of OFDM symbol. The length field defined in L-SIG may be calculated, for example, using the OFDM symbol duration 4 us. 802.1 lax may support two basic symbol durations, e.g. , 3.2us+GI and 12.8us+GI. Four (4) us may be considered as 3.2us symbol duration with 0.8 us GI as indicated by Eq. 1 :

. . T XT ime-T_Lpre amble Nsym „ „ ,

Length = * rate * 3 Eq. 1 where TXTime may be a total transmission duration of a packet in us. TX Time may be calculated based on the ¼ or ½ symbol duration, for example, when ¼ or ½ OFDM symbol duration is utilized for the last symbol. T Lpreamble may be the duration of a legacy preamble, e.g. , including L-STF, L-LTF and L-SIG, in us. Rate may be the bits per coded symbol signaled in L-SIG field. Nsym may be the number of coded symbols carried by an OFDM system utilized in legacy mode, e.g. 48 coded symbols.

[0251] A transmitter may map data to a plurality of OFDM symbols in a frame. The transmitter may measure the number of left over data symbols to be mapped to the last OFDM symbol.

[0252] FIG. 32 is an example of dynamic padding in every fourth sub-carrier (1/4 data). A plurality of OFDM symbols may have a first duration. The plurality of OFDM symbols may be associated with a first length of data. For example, each of the plurality of OFDM symbols may transmit the first length of data. Data may be placed in every fourth sub-carrier, for example, when data length (e.g. , a second length) is less than or equal to ¼ the length of a last OFDM symbol 3102. For example, a second length of data may be determined for the last OFDM symbol 3102 that is less than the first length of data. On taking an IFFT of the last OFDM symbol, the resulting time domain symbol may be periodic with four periods. The last three periods may be removed and a modified last OFDM symbol 3104 may be sent. The modified last OFDM symbol 3104 may be ¼ of the last OFDM symbol 3104. For example, the last OFDM symbol 3102 may be modified (e.g. , reduced) to the modified last OFDM symbol 3104 based on the second length of data. The last OFDM symbol 3102 may be reduced from a first duration to a second duration (e.g., such as the modified OFDM symbol 3104) based on removing excessive padding using a FFT/IFFT relationship. A cyclic prefix length used may be the same for the entire sub-frame.

[0253] FIG. 33 is an example of dynamic padding in every second sub-carrier (1/2 data). A plurality of OFDM symbols may have a first duration. The plurality of OFDM symbols may be associated with a first length of data. For example, each of the plurality of OFDM symbols may transmit the first length of data. Data may be placed in every second sub-carrier, for example, when data length (e.g. , a second length) is greater than ¼ the length of the first duration of a last OFDM symbol 3202 and less than or equal to ½ the duration of the last OFDM symbol 3202. On taking an IFFT of the OFDM symbol, the resulting time domain symbol may be periodic with two periods. The second period may be removed and a modified symbol duration 3204 may be sent. The modified symbol 3204 may be ½ of the last OFDM symbol 3202. For example, the last OFDM symbol 3202 may be modified from the first duration to a second duration (e.g. , modified OFDM symbol 3204) based on the data length. The last OFDM symbol 3202 may be reduced from a full OFDM symbol duration to a fractional OFDM symbol duration (e.g., such as the modified symbol 3204) based on removing excessive padding using a FFT/IFFT relationship. A cyclic prefix length used may be the same for the entire sub-frame.

[0254] Data may be transmitted normally, for example, when data length is greater than ½ the first length of data to be transmitted in the last OFDM symbol 3202.

[0255] FIG. 34 is an example of dynamic padding where two truncated OFDM symbols of duration ¼ and duration ½ may be transmitted (e.g. , as 3/4 data). Two truncated OFDM symbols of duration ¼ and duration ½ may be transmitted, for example, when the data is greater than ½ the first length of a last OFDM symbol 3302 but less than or equal to ¾ the first length of the last OFDM symbol 3302. Data equal to ½ the length of the last OFDM symbol 3302 may be placed in every second sub-carrier. On taking an IFFT of the OFDM symbol, the resulting time domain symbol may be periodic with two periods. The second period may be removed and a ½ symbol duration 3304 may be sent. The rest of the data may be placed in every fourth sub-carrier. On taking an IFFT of the OFDM symbol, the resulting time domain symbol may be periodic with four periods. The last three periods may be removed and a ¼ symbol duration 3306 may be sent. For example, two symbols of duration ½ and ¼ the duration of the last OFDM symbol 3302 may be transmitted. A cyclic prefix length used may be the same for the entire sub-frame.

[0256] In an example of blind estimation, a receiver may estimate the duration of the last OFDM symbol based on the length of the frame in a MAC or PHY header. In an example of signaling, a receiver may retrieve the length of the last OFDM symbol in the frame.

[0257] A receiver may map received data to a 256 length symbol, e.g. , by replicating the received signal four times, for example, when data length is less than ¼ the first length of data. Taking the FFT of the symbol, a resulting frequency domain symbol may replicate the original transmitted signal. A receiver may also take a 64 point FFT of the received signal and map it to every 4^th sub-carrier in the frequency domain. [0258] A receiver may map received data to a 256 length symbol, e.g. , by replicating the received signal two times, for example, when the data length is less than ½ the length of the last OFDM symbol. Taking the FFT of the symbol, the resulting frequency domain symbol may replicate the original transmitted signal. A receiver may also take a 128 point FFT of the received signal and map it to every 2^nd sub-carrier in the frequency domain.

[0259] A receiver may process data normally, for example, when the data length is greater than ½ the length of the OFDM symbol.

[0260] FIG. 35 is an example of dynamic padding in OFDMA transmission. Disclosed technology may be used in OFDMA transmission, for example, when STAs in an OFDMA transmission have a last transmission with one of the lengths discussed above, for example, the maximum length.

[0261] A fewer number of subcarriers used for the transmission and/or a low modulation and coding scheme may limit the maximum allowed PSDU size. For example, 9 bits may be utilized to signal the length in the SIG field in the 802.11 ah lMHz bandwidth format (e.g., 26 usable subcarriers). 9 bits may be used to signal the PSDU with up to 511 bytes or 511 OFDM symbols. 511 OFDM symbols may carry more than 511 bytes or less than 511 bytes, e.g. , depending on the modulation and coding scheme utilized. 511 OFDM symbols may carry more than 511 bytes, e.g. , when an MCS value is high and each OFDM symbol carries a large number of information bits. 511 OFDM symbols may carry less than 511 bytes, e.g., when an MCS value is low and each OFDM symbol carries a limited number of information bits. The maximum allowed PSDU size may be limited to 511 bytes (e.g., in these cases) and a TCP packet may comprise about 1500 bytes, e.g. , the PSDU size may be smaller (e.g., significantly smaller) than a TCP packet size.

[0262] A maximum allowed PSDU size may be limited (e.g., to a specific number). An example may be when OFDMA is utilized and the smallest RU has 26 subcarriers.

[0263] A length field may be carried in a SIG field (e.g., in the PLCP header). The length field may define a length of a PSDU (e.g. , current PSDU) in the units of bytes or in the units of OFDM symbols. A maximum allowed PSDU size may be limited by the design of the length field, e.g. , due to the limited size of the SIG field.

[0264] One or more length field designs may be provided. The length field may be signaled in a SIG-A and/or a SIG-B field. The length field may be extended by using one or more other fields. For example, the SIG field may comprise a length field, an MCS field, and/or an aggregation field. The length field may be in a number of bytes, e.g., when the aggregation field is OFF. The length field may be in a number of OFDM symbols, e.g. , when the aggregation field is ON.

[0265] In an example, one or more of the following may apply. Two or more MCS sets (e.g., MCS set 1 and MCS set 2) may be defined. MCS set 1 may correspond to high MCS values. MCS set 2 may correspond to low MCS values. MCS set 1 and MCS set 2 may not overlap. MCS set 1 and MCS set 2 may cover the MCS values (e.g., all the MCS values) used in the system (e.g. by the union of MCS set 1 and MCS set 2).

[0266] The value of the aggregation field may depend on the MCS sets that are used. For example, the aggregation field may be set to ON for MCS set 1. The aggregation field may be set to OFF for MCS set 2. The aggregation field may be used as a length extension field, e.g. , when the receiver obtains the value of aggregation implicitly from the MCS value. The receiver may obtain the value of aggregation implicitly from the MCS value, e.g., when the MCS set- aggregation setting mapping (e.g., described herein) is used and/or the MCS value is signaled. The bit(s) used for the aggregation field together with the original length field may be used to indicate a range of PSDU sizes (e.g. a wider range of PSDU sizes).

[0267] A network allocation vector (NAV) may include virtual carrier-sensing. A MAC header in a frame may comprise a duration field. The duration field may specify the specified transmission time required for the frame. The wireless medium may be busy, e.g. , during the transmission time. The STAs listening through the wireless medium may read the duration field and set their NAVs (e.g., according to the duration field). The NAV may indicate how long a STA defers (e.g. , must defer) from accessing the wireless medium.

[0268] More than one MAC frame may be transmitted concurrently, e.g. , when the DL MU transmission (e.g., OFDMA transmission) is present. Each MAC header may comprise a duration field. A STA may detect the PHY header that comprises a SIG-A and/or a SIG-B field. The STA may determine whether it is a potential receiver of the transmission. In the case that the STA is not an intended receiver of this DL MU transmission, e.g. , instead of refusing to receive the transmission and returning to a power saving mode, the STA may need to (e.g. , must) detect each of the MAC frames carried in this MU transmission and set its NAV accordingly. This NAV setting process may lower power efficiency. An unintended STA may determine how long it defers (e.g. must defer) without detecting each of the MAC frames.

[0269] Virtual carrier sensing may be provided. More than one expected response frames to a current DL MU transmission may exist with MU transmissions. One or more unintended STAs may take advantage of the response frame with the longest OFDM symbol duration, e.g. , to set their MU Allocation Vectors (MAVs). MAVs may indicate how long a STA defers (e.g. , must defer) from accessing the channel medium. A PLCP header (e.g., a (HE) SIG-A and/or a SIG-B field) may carry a MU response indication (MRID), e.g. with the DL MU transmission. One or more unintended STAs may use this MRID to set a MAV. For example, one or more of the following may apply at the AP side and/or the STA side.

[0270] For the AP one or more of the following may apply. The PLCP header of a DL MU transmission may comprise an MRID value. A set of MRID values may be defined to categorize different possible response frames. The response frames may include one or more of the following: UL data frames; UL management frames, e.g., Probe request, (Re-)authentication request, (Re-)association request, etc.; or UL control frames, e.g. , PS-Poll, (MU-)CTS, CF-End, ACK, block ACK, etc. Based on the size of the potential response frame, N MRID values may be defined. Each of the N MRID values may be used to indicate a duration range. The duration range may vary, e.g., in units of microseconds or multiple of microseconds. The MRID values may represent the duration range linearly. For example, MRID = 0 may indicate the duration range [0, D-l], MRID = 1 may indicate the duration range [D, 2D-1], and so on. The MRID values may represent the duration range exponentially. For example, MRID =0 may indicate the duration range [0, 2^AD-1], MRID = 1 may indicate the duration range [2^AD, 2^A(2D)-1], and so on. With MU transmission, the AP may schedule one or more UL MU response frames. With MU transmission, the AP may estimate the response frame sizes. The AP may identify the longest transmit duration from the UL users (e.g., each of the UL users). The longest transmission duration may be a function of the response frame size, the MCS assigned or suggested for the UL frame transmission, and/or the resource allocated for the UL frame transmission. The AP may determine an MRID value by comparing the longest transmission duration with the duration range.

[0271] For the STA side, one or more of the following may apply. The STA may receive resource allocation information in the PLCP header, e.g. , when the STA is an intended receiver of the DL MU transmission. The STA may receive and/or detect the TCP packet on one or more assigned Rus accordingly. The STA may check the MRID value in the PLCP header, e.g., when the STA is not an intended receiver of the DL MU transmission. An MRID counter may start at the end of the DL MU transmission. The DL MU PPDU(s) may comprise one or more PSDUs where each PSDU may include its own duration field (e.g. , in its corresponding MAC header). One or more of the following may apply (e.g., when PSDU(s) carried by the MU PPDU comprise their own duration fields): the STA may defer based on the longest NAV value, e.g. , when the STA detects each of the PSDUs successfully; or the STA may defer based on the MAV and ignore obtained NAVs, e.g., when the STA does not detect each of the PSDUs in the DL MU transmission.

[0272] The processes and instrumentalities described herein may apply in any combination, may apply to other wireless technologies, and for other services.

[0273] Although disclosed features, elements and techniques (e.g. disclosed technologies) are described in various examples with various combinations, each feature, element or technique may be implemented alone and in various combinations with and without other described features, elements and techniques.

[0274] Although examples are presented with respect to 802.11, the disclosed technologies are applicable to other wireless systems and protocols.

[0275] Although examples are presented with Short Inter Frame Space (SIFS) to indicate various inter frame spacing, the disclosed technologies may be applied with other inter frame spacing, such as Reduced Inter Frame Space (RIFS) or other agreed time intervals.

[0276] A WTRU may refer to an identity of the physical device, or to the user's identity such as subscription related identities, e.g., MSISDN, SIP URI, etc. WTRU may refer to application- based identities, e.g. , user names that may be used per application.

[0277] The processes described above may be implemented in a computer program, software, and/or firmware incorporated in a computer-readable medium for execution by a computer and/or processor. Examples of computer-readable media include, but are not limited to, electronic signals (transmitted over wired and/or wireless connections) and/or computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as, but not limited to, internal hard disks and removable disks, magneto-optical media, and/or optical media such as CD-ROM disks, and/or digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, terminal, base station, RNC, and/or any host computer.

Claims

CLAIMS What is Claimed:

1. A method of transmitting a protocol data unit (PDU), the method comprising:

mapping data to a plurality of OFDM symbols of the PDU, wherein each of the plurality of OFDM symbols are associated with a first duration, and wherein each of the plurality of OFDM symbols are associated with a first length of data;

determining that a second length of data to be transmitted in a last OFDM symbol of the plurality of OFDM symbols is less than or equal to ¼, ½, or ¾ of the first length of data;

modifying, based on the second length of data, the last OFDM symbol from the first duration to a second duration, wherein the second duration is ¼, ½, or ¾ of the first duration; and sending, in a PHY header, an indication of the second duration associated with the last OFDM symbol, wherein the indication indicates that the second duration is ¼, ½, or ¾ of the first duration.

2. The method of claim 1, wherein the last OFDM symbol is modified to ¼ of the first duration when the second length of data is less than or equal to ¼ of the first length of data.

3. The method of claim 1, wherein the last OFDM symbol is modified to ½ of the first duration when the second length of data is greater than ¼ the first length of data and less than or equal to ½ the first length of data.

4. The method of claim 1, wherein the last OFDM symbol is modified to ¾ of the first duration when the second length of data is greater than ½ the first length of data and less than or equal to ¾ the first length of data.

5. The method of claim 1, wherein modifying the last OFDM symbol from the first duration to the second duration comprises using an inverse FFT (IFFT) relationship to produce the second duration for the last OFDM symbol in the time domain.

6. The method of claim 5, wherein modifying the last OFDM symbol from the first duration to the second duration further comprises removing one or more redundant periods that result from using the IFFT relationship.

7. The method of claim 1, further comprising creating a periodic symbol based on the second duration of the last OFDM symbol.

8. The method of claim 1, wherein the first length of data is associated with a maximum data length carried within one OFDM symbol.

9. The method of claim 1, wherein the PDU is a physical layer convergence procedure (PLCP) PDU (PPDU).

10. The method of claim 1, wherein the first length of data and the second length of data are associated with a number of available carriers.

11. The method of claim 1, wherein the indication indicates that the second duration is equal to the first duration when the second length of data is greater than ¾ of the first length of data.

12. An access point (AP) comprising:

a processor configured to:

map data to a plurality of OFDM symbols of a protocol data unit (PDU), wherein each of the plurality of OFDM symbols are associated with a first duration, and wherein each of the plurality of OFDM symbols are associated with a first length of data;

determine a second length of data to be transmitted in a last OFDM symbol of the plurality of OFDM symbols is less than or equal to ¼, ½, or ¾ of the first length of data; modify, based on the second length of data, the last OFDM symbol from the first duration to a second duration, wherein the second duration is ¼, ½, or ¾ of the first duration; and

send, in a PHY header, an indication of the second duration associated with the last OFDM symbol, wherein the indication indicates that the second duration is ¼, ½, or ¾ of the first duration.

13. The AP of claim 12, wherein the last OFDM symbol is modified to ¼ of the first duration when the second length of data is less than or equal to ¼ of the first length of data.

14. The AP of claim 12, wherein the last OFDM symbol is modified to ½ of the first duration when the second length of data is greater than ¼ the first length of data and less than or equal to ½ the first length of data.

15. The AP of claim 12, wherein the last OFDM symbol is modified to ¾ of the first duration when the second length of data is greater than ½ the first length of data and less than or equal to ¾ the first length of data.

16. The AP of claim 12, wherein being configured to modify the last OFDM symbol from the first duration to the second duration comprises use of an inverse fast Fourier transform (IFFT) relationship to produce the second duration for the last OFDM symbol in the time domain.

17. The AP of claim 16, wherein being configured to modify the last OFDM symbol from the first duration to the second duration further comprises being configured to remove one or more redundant periods that result from using the IFFT relationship.

18. The AP of claim 12, wherein the processor is further configured to create a periodic symbol based on the second duration of the last OFDM symbol.

19. The AP of claim 12, wherein the first length of data is associated with a maximum data length carried within one OFDM symbol.

20. The AP of claim 12, wherein the PDU is a physical layer convergence procedure (PLCP) PDU (PPDU).

21. The AP of claim 12, wherein the first length of data and the second length of data are associated with a number of available carriers.

22. The AP of claim 12, wherein the indication indicates that the second duration is equal to the first duration when the second length of data is greater than ¾ of the first length of data.