Patent Publication Number: US-2015063251-A1

Title: Methods and apparatus for extending a reverse direction grant on a wireless network

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/872,334, filed Aug. 30, 2013, and entitled “METHODS AND APPARATUS FOR EXTENDING A REVERSE DIRECTION GRANT ON A WIRELESS NETWORK,” and to U.S. Provisional Application No. 61/899,841, filed Nov. 4, 2013, and entitled “METHODS AND APPARATUS FOR EXTENDING A REVERSE DIRECTION GRANT ON A WIRELESS NETWORK,” and to U.S. Provisional Application No. 61/900,936, filed Nov. 6, 2013, and entitled “METHODS AND APPARATUS FOR EXTENDING A REVERSE DIRECTION GRANT ON A WIRELESS NETWORK,” and to U.S. Provisional Application No. 61/976,478, filed Apr. 7, 2014, and entitled “METHODS AND APPARATUS FOR EXTENDING A REVERSE DIRECTION GRANT ON A WIRELESS NETWORK,” all of which are assigned to the assignee hereof. The disclosures of these prior applications are considered part of this application, and are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field 
     The present application relates generally to wireless communications, and more specifically to systems, methods, and devices for allocating a wireless transmission medium between a first and a second wireless device. 
     2. Background 
     In many telecommunication systems, communications networks are used to exchange messages among several interacting spatially-separated devices. Networks may be classified according to geographic scope, which could be, for example, a metropolitan area, a local area, or a personal area. Such networks would be designated respectively as a wide area network (WAN), metropolitan area network (MAN), local area network (LAN), wireless local area network (WLAN), or personal area network (PAN). Networks also differ according to the switching/routing technique used to interconnect the various network nodes and devices (e.g. circuit switching vs. packet switching), the type of physical media employed for transmission (e.g. wired vs. wireless), and the set of communication protocols used (e.g. Internet protocol suite, SONET (Synchronous Optical Networking), Ethernet, etc.). 
     Wireless networks are often preferred when the network elements are mobile and thus have dynamic connectivity needs, or if the network architecture is formed in an ad hoc, rather than fixed, topology. Wireless networks employ intangible physical media in an unguided propagation mode using electromagnetic waves in the radio, microwave, infra-red, optical, etc. frequency bands. Wireless networks advantageously facilitate user mobility and rapid field deployment when compared to fixed wired networks. 
     A transmission medium in a wireless network may have a limited capacity. The transmission medium capacity may be allocated to nodes of the wireless network using a variety of protocols or methods. In some instances, a portion of the medium&#39;s transmission capacity may be allocated to a wireless node, but may be in excess of the transmission capacity needed by the node at a particular time. This may result in some portions of the medium&#39;s transmission capacity being unused. Thus, improved systems, methods, and devices for allocating transmission capacity in a wireless network are desired. 
     SUMMARY 
     The systems, methods, and devices of the invention each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this invention provide advantages that include improved communications between first and second devices in a wireless network. In an embodiment, the first and second devices may be access points and stations in the wireless network. 
     One innovative aspect includes a method A method of wireless communication. The method includes transmitting, via a first device, a first message, the first message indicating a duration of a transmission opportunity of the first device, receiving, via the first device, a second message; and decoding, via the first device, the second message to determine a new duration of the transmission opportunity. In some aspects, the method also includes generating the first message as one of a request-to-send message, a ps-poll frame, or a trigger frame. In some aspects, the method includes decoding the second message as a clear-to-send message, or as a request-to-send message. In some aspects, the method includes transmitting a third message indicating whether a second device has permission to extend the duration of the transmission opportunity. In some aspects, the method includes generating the first message to indicate whether the first device grants permission to utilize at least a portion of the transmission opportunity to relay data transmitted by the first device. In some aspects, permission is indicated in an order field or a relayed frame field of the first message. Some aspects of the method also include decoding the second message to determine whether an explicit or implicit acknowledgment procedure is used for the relayed data, transmitting a data packet during the transmission opportunity; and determining whether the data packet is acknowledged based on the acknowledgment procedure. In some aspects, the method includes determining a NAV expiration time based on the duration field of the second message; determining the acknowledgement procedure is explicit if the determined NAV expiration time is different than a NAV expiration time indicated by the duration field of the first message; and determining the acknowledgment procedure is implicit if the determined NAV expiration time is the same as the NAV expiration time indicated by the duration field of the first message. 
     Another aspect disclosed is an apparatus for wireless communication. The apparatus includes a transmitter configured to transmit a first message, the first message indicating a duration of a transmission opportunity of the apparatus, a receiver configured to receive a second message; and a processing system configured to decode the second message to determine a new duration of the transmission opportunity. In some aspects, the transmitter is further configured to transmit a third message indicating whether a second device has permission to extend the duration of the transmission opportunity. In some aspects, the processing system is further configured to generate the first message to indicate whether the first device grants permission to utilize at least a portion of the transmission opportunity to relay data transmitted by the first device. In some aspects, the processing system is further configured to indicate whether the permission is granted in an order field or a relayed frame field of the first message. In some aspects, the processing system is further configured to decode the second message to determine whether an explicit or implicit acknowledgment procedure is used for the relayed data, and determine whether a transmitted data packet is acknowledged based on the determined acknowledgment procedure. In some aspects, the processing system is further configured to determine a NAV expiration time based on the duration field of the second message, determine the acknowledgement procedure is explicit if the determined NAV expiration time is different than a NAV expiration time indicated by the duration field of the first message; and determine the acknowledgment procedure is implicit if the determined NAV expiration time is the same as the NAV expiration time indicated by the duration field of the first message. 
     Another aspect disclosed is a method of wireless communication. The method includes receiving, via a first device, a first message, decoding the first message to determine a duration of a transmission opportunity of a second device, generating, via the first device, a second message, the second message indicating a new duration of the transmission opportunity; and transmitting the second message. In some aspects, the method also includes receiving a third message; and decoding the third message to determine whether the first device has permission to extend the duration of the transmission opportunity. In some aspects, the method also includes decoding the first message to determine whether permission is granted to relay data transmitted by the second device during the transmission opportunity. In some aspects, the method also includes generating the second message to indicate an acknowledgment procedure for the relayed data, receiving data from the second device; and acknowledging the data based on the indicated acknowledgment procedure. 
     Some aspects of the method include determining use of an explicit acknowledgment procedure for the received data; and generating the second message to indicate an extended NAV duration relative to a NAV duration indicated by the first message based on a duration field of the second message. 
     Some aspects of the method also include determining a duration field of the second message based on an estimated time for a transmission of the data received from the second device, the duration of the transmission opportunity of the second device, and an amount of time remaining in the transmission opportunity, and indicating the extended NAV duration in the duration field of the second message. 
     Some aspects of the method also include determining use of an implicit acknowledgment procedure for the received data; and generating the second message to indicate an unchanged NAV duration relative to a NAV duration indicated by the first message based on a duration field of the second message. In some aspects, the method also includes transmitting a request-to-send message to a third device in response to receiving the data if the second message indicates an implicit acknowledgment procedure. 
     Another aspect disclosed is an apparatus for wireless communication. The apparatus includes a receiver configured to receive a first message, a processing system configured to decode the first message to determine a duration of a transmission opportunity of a second device, and to generate a second message indicating a new duration of the transmission opportunity; and a transmitter configured to transmit the second message. In some aspects, the processing system is further configured to decode the first message as one of a request-to-send message, a ps-poll frame, or a trigger frame. In some aspects, the processor is further configured to decode the first message to determine whether permission is granted to relay data transmitted by the second device during the transmission opportunity. In some aspects, the processor is further configured to generate the second message to indicate an acknowledgment procedure for the relayed data, receive data from the second device; and acknowledge the data based on the indicated acknowledgment procedure. In some aspects of the apparatus, the processor is further configured to determine use of an explicit acknowledgment procedure for the received data; and generate the second message to indicate an extended NAV duration relative to a NAV duration indicated by the first message. 
     In some aspects of the apparatus, the processor is further configured to determine a duration field of the second message based on an estimated time for a transmission of the data received from the second device, the duration of the transmission opportunity of the second device, and an amount of time remaining in the transmission opportunity, and indicate the extended NAV duration in the duration field of the second message. In some aspects of the apparatus, the processor is further configured to determine use of an implicit acknowledgment procedure for the received data; and generate the second message to indicate an unchanged NAV duration relative to a NAV duration indicated by the first message based on a duration field of the second message. In some aspects of the apparatus, the transmitter is further configured to transmit a request-to-send message to a third device in response to receiving the data if the second message indicates an implicit acknowledgment procedure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exemplary wireless communication system  100 . The wireless communication system may operate pursuant to a wireless standard, for example any one of the 802.11 standards. 
         FIG. 2  shows an exemplary functional block diagram of a wireless device that may be employed within the wireless communication system of  FIG. 1 . 
         FIG. 3A  is a timing diagram of a message exchange allocating a transmission medium between a first and second wireless device. 
         FIG. 3B  is a timing diagram of a message exchange allocating a transmission medium between a first and second wireless device. 
         FIG. 3C  is a timing diagram of one embodiment of a message exchange allocating a data communications medium between an access point and a station. 
         FIG. 3D  shows a format of an exemplary request-to-send (RTS) frame. 
         FIG. 3E-1  shows a format of an exemplary acknowledgment frame. 
         FIG. 3E-2  shows an alternative format of a frame control field of the acknowledgment frame of  FIG. 3E-1 . 
         FIG. 3F  is a timing diagram of one embodiment of a message exchange allocating a data communications medium between an access point and a station. 
         FIG. 3G  is a timing diagram of one embodiment of a message exchange allocating a data communications medium between an access point and a station. 
         FIG. 3H  is a timing diagram of one embodiment of a message exchange allocating a data communications medium between an access point and a station. 
         FIG. 3I  is a timing diagram of one embodiment of a message exchange allocating a data communications medium between an access point and a station. 
         FIG. 4A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless network. 
         FIG. 4B  is a functional block diagram of an exemplary device that may be employed within a wireless communication system. 
         FIG. 5A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless network. 
         FIG. 5B  is a functional block diagram of an exemplary device that may be employed within a wireless communication system. 
         FIG. 6A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless network. 
         FIG. 6B  is a functional block diagram of an exemplary device that may be employed within a wireless communication system. 
         FIG. 7A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless network. 
         FIG. 7B  is a functional block diagram of an exemplary device that may be employed within a wireless communication system. 
         FIG. 8A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless network. 
         FIG. 8B  is a functional block diagram of an exemplary device that may be employed within a wireless communication system. 
         FIG. 9A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless network. 
         FIG. 9B  is a functional block diagram of an exemplary device that may be employed within a wireless communication system. 
         FIG. 10A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless network. 
         FIG. 10B  is a functional block diagram of an exemplary device that may be employed within a wireless communication system. 
         FIG. 11A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless communication network. 
         FIG. 11B  is a functional block diagram of an exemplary device  1150  that may be employed within the wireless communication system  100 . 
         FIG. 12A  is a flowchart of a process for relaying data over a wireless communications network. 
         FIG. 12B  is a functional block diagram of an exemplary device  1250  that may be employed within the wireless communication system  100 . 
     
    
    
     DETAILED DESCRIPTION 
     Various aspects of the novel systems, apparatuses, and methods are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the novel systems, apparatuses, and methods disclosed herein, whether implemented independently of, or combined with, any other aspect of the invention. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the invention is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the invention set forth herein. It should be understood that any aspect disclosed herein may be embodied by one or more elements of a claim. 
     Although particular aspects are described herein, many variations and permutations of these aspects fall within the scope of the disclosure. Although some benefits and advantages of the preferred aspects are mentioned, the scope of the disclosure is not intended to be limited to particular benefits, uses, or objectives. Rather, aspects of the disclosure are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of the preferred aspects. The detailed description and drawings are merely illustrative of the disclosure rather than limiting, the scope of the disclosure being defined by the appended claims and equivalents thereof. 
     Popular wireless network technologies may include various types of wireless local area networks (WLANs). A WLAN may be used to interconnect nearby devices together, employing widely used networking protocols. The various aspects described herein may apply to any communication standard, such as a wireless protocol. 
     In some aspects, wireless signals in a sub-gigahertz band may be transmitted according to the 802.11 protocol using orthogonal frequency-division multiplexing (OFDM), direct-sequence spread spectrum (DSSS) communications, a combination of OFDM and DSSS communications, or other schemes. Implementations of the 802.11 protocol may be used for sensors, metering, and smart grid networks. Advantageously, aspects of certain devices implementing the 802.11 protocol may consume less power than devices implementing other wireless protocols, and/or may be used to transmit wireless signals across a relatively long range, for example about one kilometer or longer. 
     In some implementations, a WLAN includes various devices which are the components that access the wireless network. For example, there may be two types of devices: access points (“APs”) and clients (also referred to as stations, or “STAs”). In general, an AP may serve as a hub or base station for the WLAN and a STA serves as a user of the WLAN. For example, a STA may be a laptop computer, a personal digital assistant (PDA), a mobile phone, etc. In an example, a STA connects to an AP via a WiFi (e.g., IEEE 802.11 protocol such as 802.11) compliant wireless link to obtain general connectivity to the Internet or to other wide area networks. In some implementations a STA may also be used as an AP. 
     An access point (“AP”) may also comprise, be implemented as, or known as a NodeB, Radio Network Controller (“RNC”), eNodeB, Base Station Controller (“BSC”), Base Transceiver Station (“BTS”), Base Station (“BS”), Transceiver Function (“TF”), Radio Router, Radio Transceiver, or some other terminology. 
     A station “STA” may also comprise, be implemented as, or known as an access terminal (“AT”), a subscriber station, a subscriber unit, a mobile station, a remote station, a remote terminal, a user terminal, a user agent, a user device, user equipment, or some other terminology. In some implementations an access terminal may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol (“SIP”) phone, a wireless local loop (“WLL”) station, a personal digital assistant (“PDA”), a handheld device having wireless connection capability, or some other suitable processing device connected to a wireless modem. Accordingly, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or smartphone), a computer (e.g., a laptop), a portable communication device, a headset, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a gaming device or system, a global positioning system device, or any other suitable device that is configured to communicate via a wireless medium. 
     As discussed above, certain of the devices described herein may implement any one of the 802.11 standards, for example. Such devices, whether used as a STA or AP or other device, may be used for smart metering or in a smart grid network. Such devices may provide sensor applications or be used in home automation. The devices may instead or in addition be used in a healthcare context, for example for personal healthcare. They may also be used for surveillance, to enable extended-range Internet connectivity (e.g. for use with hotspots), or to implement machine-to-machine communications. 
     Some embodiments of wireless network may experience asymmetric traffic and data rates. For example, because access points may be able to transmit with relatively high power, transmissions from a second wireless device may achieve a high data rate for downlink traffic. In some embodiments, stations may be of relatively lower power and may sustain lower data rates for uplink traffic. 
     Additionally, some stations may be power constrained. To minimize a station&#39;s power usage, it may be desirable to improve a station&#39;s ability to operate in a sleep state to extend the battery life of the station. One method to increase the time a station may operate in a sleep state is to reduce the time required for a station to uplink data to a second wireless device. 
     In some wireless networks, for example 802.11 networks, a station may transmit data by either transmitting during a contention time period or by reserving a transmission opportunity during a contention free time period. If data is transmitted during a contention time period, a collision may result from the transmission. A collision may then require a station to delay transmission according to one or more collision resolution methods. This may inhibit the station&#39;s ability to enter a sleep state until the collision is resolved and the data is successfully transmitted. 
     If the station reserves a transmission opportunity during a contention free time period, the station may also be inhibited from entering a sleep state for a time period. For example, one method of reserving a content free transmission opportunity is to transmit a request-to-send message. A second wireless device controlling access to the medium during the contention free period may respond with a clear-to-send message. This may then provide a transmission opportunity for the station. However, transmitting the request-to-send message, if transmitted during a contention period, may result in a collision that, as discussed above, may consume additional time to resolve. The station may also be inhibited from entering a sleep state until it receives at least the clear to send message from the access point, also inhibiting the station&#39;s ability to enter a sleep state. 
     Proposed herein are methods, apparatus, and systems that provide for a first wireless device to request a reverse direction grant (RDG) from a second wireless devices to improve the utilization of a wireless data communications medium during a transmission opportunity (TXOP) of the second wireless device. The reverse direction protocol enables the second wireless device to grant permission for a first wireless device to transmit data during a transmission opportunity time period reserved for transmissions of the second wireless device. By utilizing at least a portion of the second wireless device&#39;s transmission opportunity, the time necessary for a first wireless device to uplink data to a second wireless device may be reduced. This reduction in time can provide for longer sleep periods and thus a longer battery life of the first wireless device. While in the following description of the disclosed embodiments the first wireless device may be referred to as the station and the second wireless device will be referred to as the access point, those skilled in the art will appreciate that the methods described herein may be applied to any two types of wireless devices. 
     In an embodiment, the amount of data a wireless device is waiting to send may be insufficient to consume all of the time available in the wireless device&#39;s transmission opportunity when the waiting data is transmitted. The time remaining in the transmission opportunity after all of its own data has been sent may be allocated to one or more other wireless devices. An ability for another wireless device to request use of a portion of the wireless device&#39;s transmission opportunity is described below. 
     A station operating on a wireless network may awake from a sleep state and send a message to a second wireless device to determine if the second wireless device has any data waiting to be sent to the station. In an embodiment, the message sent to the second wireless device is a “ps-poll” message or in general, a trigger frame. Proposed is a request message sent from a first wireless device to a second wireless device that includes an indication that the first wireless device is requesting a reverse direction grant from the second wireless device. This request message may be considered a reverse direction grant request. If granted, the first wireless device is permitted to transmit data during a portion of a transmission opportunity of the second wireless device. 
     In another embodiment the reverse direction grant request may be implicit and agreed to beforehand (for example during an association) between the first and second wireless devices. In some aspects, whether the first and/or second wireless device will support the reverse direction grant request may be negotiated between the first and/or second wireless device before the reverse direction grant request is transmitted. For example, the first and second wireless devices may exchange management frames to negotiate whether reverse direction grant requests will be exchanged. In some aspects, the negotiation may define time periods when a device may provide a reverse direction grant. In some aspects, these time periods may be repeating or periodic. 
     In one embodiment, the request message is a “ps-poll” or the trigger frame. In this embodiment, the reverse direction grant request can be indicated by a “more data” bit or an uplink data indication included in the ps-poll message. In one aspect, this indication may be a single bit specifying whether or not the first wireless device has buffered uplink data. In other aspects, more bits may be used as an indication that the first wireless device has buffered uplink data. The multiple bits may be used to indicate not only that the first wireless device has buffered uplink data, but also the amount of data buffered for uplink. In one aspect, the multiple bit indication may indicate an estimated transmission time as a multiple of a time unit. For example in an aspect utilizing a 9 bit indication, the first wireless device can indicate that up to 512 TUs (e.g., symbols) may be necessary to transmit its buffered uplink data. 
     By utilizing a portion of a second wireless device&#39;s transmission opportunity to transmit data, the first wireless device may transmit with reduced risk of delays associated with collisions, as the transmission opportunity has previously been reserved for transmissions by the second wireless device. Additionally, the disclosed method of allocating a data communications medium for the first wireless device&#39;s transmission may be relatively efficient compared to other methods as described above. For example, the request by the first wireless device for a reverse direction grant may in some embodiments be embedded in an existing control frame exchange between the first and second wireless devices. Thus, the first wireless device may be able to obtain permission to transmit during a transmission opportunity of the second wireless device without transmitting any additional messages on the wireless network. 
       FIG. 1  shows an exemplary wireless communication system  100 . The wireless communication system  100  may operate pursuant to a wireless standard, for example the 802.11 standards. The wireless communication system  100  may include an AP  104 , which communicates with STAs  106 . 
     A variety of processes and methods may be used for transmissions in the wireless communication system  100  between the AP  104  and the STAs  106 . For example, signals may be sent and received between the AP  104  and the STAs  106  in accordance with OFDM/OFDMA techniques. If this is the case, the wireless communication system  100  may be referred to as an OFDM/OFDMA system. Alternatively, signals may be sent and received between the AP  104  and the STAs  106  in accordance with CDMA techniques. If this is the case, the wireless communication system  100  may be referred to as a CDMA system. 
     A communication link that facilitates transmission from the AP  104  to one or more of the STAs  106  may be referred to as a downlink (DL)  108 , and a communication link that facilitates transmission from one or more of the STAs  106  to the AP  104  may be referred to as an uplink (UL)  110 . Alternatively, a downlink  108  may be referred to as a forward link or a forward channel, and an uplink  110  may be referred to as a reverse link or a reverse channel. 
     The AP  104  may act as a base station and provide wireless communication coverage in a basic service area (BSA)  102 . The AP  104  along with the STAs  106  associated with the AP  104  and that use the AP  104  for communication may be referred to as a basic service set (BSS). It should be noted that the wireless communication system  100  may not have a central AP  104 , but rather may function as a peer-to-peer network between the STAs  106 . Accordingly, the functions of the AP  104  described herein may alternatively be performed by one or more of the STAs  106 . 
     The AP  104  may transmit a beacon signal (or simply a “beacon”), via a communication link such as the downlink  108 , to other nodes STAs  106  of the system  100 , which may help the other nodes STAs  106  to synchronize their timing with the AP  104 , or which may provide other information or functionality. Such beacons may be transmitted periodically. In one aspect, the period between successive transmissions may be referred to as a superframe. Transmission of a beacon may be divided into a number of groups or intervals. In one aspect, the beacon may include, but is not limited to, such information as timestamp information to set a common clock, a peer-to-peer network identifier, a device identifier, capability information, a superframe duration, transmission direction information, reception direction information, a neighbor list, and/or an extended neighbor list, some of which are described in additional detail below. Thus, a beacon may include information both common (e.g. shared) amongst several devices, and information specific to a given device. 
     In some aspects, a STA  106  may be required to associate with the AP  104  in order to send communications to and/or receive communications from the AP  104 . In one aspect, information for associating is included in a beacon broadcast by the AP  104 . To receive such a beacon, the STA  106  may, for example, perform a broad coverage search over a coverage region. A search may also be performed by the STA  106  by sweeping a coverage region in a lighthouse fashion, for example. After receiving the information for associating, the STA  106  may transmit a reference signal, such as an association probe or request, to the AP  104 . In some aspects, the AP  104  may use backhaul services, for example, to communicate with a larger network, such as the Internet or a public switched telephone network (PSTN). 
     During transmission of downlink data from an AP  104  to a STA  106 , data may be transmitted from the AP  104  to the STA  106  during a transmission opportunity of the access point. The AP  104  may indicate in one or more data transmissions to the STA  106  that it is granting the STA  104  a reverse direction grant. This reverse direction grant is not provided in response to a request by the STA  104 , but instead is provided independently by the AP  104  to allow the STA  104  to send an acknowledgement message for one or more data messages sent to the STA  104  by the AP  104  during the transmission opportunity of the AP  104 . By allowing acknowledgement messages to be sent during the transmission opportunity of the AP  104 , downlink data may be sent by the AP  104  during the transmission opportunity without providing a separate transmission opportunity to the STA  106  to acknowledge the data. This may improve throughput and data communication medium utilization. 
     Proposed herein is a feature of a first wireless device to request permission to transmit data during a transmission opportunity of a second wireless device. In some embodiments, the first wireless device may be the STA  106  discussed above. In some embodiments, the second wireless device may be AP  104  discussed above. This may improve transmission media utilization and reduce the amount of time a STA  106  in inhibited from entering a sleep state. 
       FIG. 2  shows an exemplary functional block diagram of a wireless device  202  that may be employed within the wireless communication system  100  of  FIG. 1 . The wireless device  202  is an example of a device that may be configured to implement the various methods described herein. For example, the wireless device  202  may comprise the AP  104 , or one of the STAs  106 . The wireless device  202  may comprise a first wireless device or a second wireless device. 
     The wireless device  202  may include a processor  204  which controls operation of the wireless device  202 . The processor  204  may also be referred to as a central processing unit (CPU). Memory  206 , which may include both read-only memory (ROM) and random access memory (RAM), may provide instructions and data to the processor  204 . A portion of the memory  206  may also include non-volatile random access memory (NVRAM). The processor  204  typically performs logical and arithmetic operations based on program instructions stored within the memory  206 . The instructions in the memory  206  may be executable to implement the methods described herein. 
     The processor  204  may comprise or be a component of a processing system implemented with one or more processors. The one or more processors may be implemented with any combination of general-purpose microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate array (FPGAs), programmable logic devices (PLDs), controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable entities that can perform calculations or other manipulations of information. 
     The processing system may also include machine-readable media for storing software. Software shall be construed broadly to mean any type of instructions, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (e.g., in source code format, binary code format, executable code format, or any other suitable format of code). The instructions, when executed by the one or more processors, cause the processing system to perform the various functions described herein. 
     The wireless device  202  may also include a housing  208  that may include a transmitter  210  and/or a receiver  212  to allow transmission and reception of data between the wireless device  202  and a remote location. The transmitter  210  and receiver  212  may be combined into a transceiver  214 . An antenna  216  may be attached to the housing  208  and electrically coupled to the transceiver  214 . The wireless device  202  may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers, and/or multiple antennas. 
     The wireless device  202  may also include a signal detector  218  that may be used in an effort to detect and quantify the level of signals received by the transceiver  214 . The signal detector  218  may detect such signals as total energy, energy per subcarrier per symbol, power spectral density and other signals. The wireless device  202  may also include a digital signal processor (DSP)  220  for use in processing signals. The DSP  220  may be configured to generate a packet for transmission. In some aspects, the packet may comprise a physical layer data unit (PPDU). 
     The wireless device  202  may further comprise a user interface  222  in some aspects. The user interface  222  may comprise a keypad, a microphone, a speaker, and/or a display. The user interface  222  may include any element or component that conveys information to a user of the wireless device  202  and/or receives input from the user. 
     The various components of the wireless device  202  may be coupled together by a bus system  226 . The bus system  226  may include a data bus, for example, as well as a power bus, a control signal bus, and a status signal bus in addition to the data bus. Those of skill in the art will appreciate the components of the wireless device  202  may be coupled together or accept or provide inputs to each other using some other mechanism. 
     Although a number of separate components are illustrated in  FIG. 2 , those of skill in the art will recognize that one or more of the components may be combined or commonly implemented. For example, the processor  204  may be used to implement not only the functionality described above with respect to the processor  204 , but also to implement the functionality described above with respect to the signal detector  218  and/or the DSP  220 . Further, each of the components illustrated in  FIG. 2  may be implemented using a plurality of separate elements. 
     The wireless device  202  may comprise an AP  104 , or a STA  106 , and may be used to transmit and/or receive communications. That is, either AP  104 , or STA  106 , may serve as transmitter or receiver devices. Certain aspects contemplate signal detector  218  being used by software running on memory  206  and processor  204  to detect the presence of a transmitter or receiver. 
       FIG. 3A  is a timing diagram of one embodiment of a message exchange allocating a data communications medium between an access point and a station. In some aspects, the messages exchanged in  FIG. 3A  may be preceded by a negotiation between the AP and the STA defining whether a reverse direction grant request transmitted by the STA is supported. The timing diagram starts at the left with a station (STA) sending a reverse direction grant request message  305  to the access point. The reverse direction grant request message requests permission for the station to transmit data during a transmission opportunity of a second wireless device. In an embodiment, the message  305  may be a “ps-poll” message or any trigger frame. In an embodiment, the request message  305  includes an indication of a duration of time for which permission to transmit is sought by the station. For example, in an embodiment, the station may determine an amount of data available to transmit. The station may then determine a duration of time required to transmit the amount of data. In one aspect, the duration may be indicated in an uplink data indication (UDI) field of a ps-poll message. The station may then specify the duration in the request  305 . In an embodiment, the station may include in the request  305  the amount of data available to transmit and the intended MCS to be used for transmitting the data. In another embodiment the devices may implicitly agree (for example during association) to reserve the remaining portion of their TXOP to each other. In some aspects, the devices may exchange management frames to negotiate whether a remaining portion of a TXOP may be granted to one device by another. In some aspects, this negotiation may be performed via the exchange of management frames. Similarly, a duration value may also be negotiated beforehand or the access point may allocate the maximum TXOP for each transmission opportunity. 
     The access point then transmits an acknowledgement message  306  to the station acknowledging the RDG request message  305 . The acknowledgement message  306  may include an indication that permission to transmit during a transmit opportunity of the access point is granted. In an embodiment, the acknowledgment message  306  may also include a duration field, indicating a period of time for which the station has permission to transmit during a transmission opportunity of the access point. In an embodiment, the acknowledgement message  306  may include a delay field, indicating a period of time after which the access point expects the station to be able to transmit during the transmission opportunity of the access point. In an embodiment, the delay field may indicate a duration of time after which the access point will initiate packet exchange with the station. In an embodiment, the station may sleep for a time period based on the delay after receiving the acknowledgement message  306 . 
     In an embodiment, the ACK message  306  may include a reverse direction MCS field which may be used by the station for rate adaptation purposes. The reverse direction MCS can be calculated with any method based on the SNR of the received RDG request message  305  or any other rate adaptation metric. In addition the access point may use the reverse direction MCS field to correctly calculate the Network Allocation Vector (NAV) to be allocated for reverse direction data. In one embodiment the delay field may have a zero (0) value indicating that the data exchange may begin at a SIFS time after the ACK is sent. 
     In the illustrated embodiment, the acknowledgement message  306  may include a “more data” indication that is set, indicating that the station should expect data to be transmitted from the AP  104  to the station  106  before the STA  106  can transmit during an AP  104  transmission opportunity. In an embodiment (not shown), the acknowledgement  306  may include an indication that the requested reverse direction grant was not granted. In this embodiment, the acknowledgement  306  may also include a sleep field (which may be the same delay field discussed above), indicating an amount of time the station may sleep before receiving data from the access point. In this embodiment, the station may sleep for a time period based on the sleep field. After the station wakes from the sleep period, it may send a ps-poll message to the access point. In an embodiment, no ps-poll message will be sent in response to the station waking up, but the station may instead wait for data to be transmitted to the station by the access point. 
     In the illustrated embodiment, the wireless medium then enters a contention period  310 . After the contention period  310 , a transmission opportunity of the access point  315  begins. During the transmission opportunity of the access point  315 , the access point  104  transmits data  320  to the station  106 . In an embodiment, AP  104  transmitting data  320  to the STA  106  is consistent with a “more data” indication in the acknowledgement message  306  discussed above. The data  320  may include an indication that the station is granted permission to transmit during the transmission opportunity of the access point  315 . For example, a bit in a packet header (e.g., RDG/More PPDU bit) of the data may be reserved for the indication. When the bit is set, it may indicate permission is granted. The station responds to the data  320  with an acknowledgement packet  330 . In another embodiment the station may immediately respond with its own data using the reverse direction grant and may piggyback the acknowledgement with the data. In other embodiments different types of reverse direction grant protocols may be used. 
     While the access point is shown transmitting a data packet  320  at the start of the transmission opportunity  315 , in some embodiments, the access point may have no data to send. This indication may be consistent with the more data indication in the ack message. An example of this is shown in  FIG. 3B  below. 
     After transmitting the acknowledgment packet  330 , the station transmits data  335  during the transmission opportunity of the access point  315 . The data  335  may include one or more separate data packets. In an embodiment, the data  335  may be addressed to the access point (shown). In an embodiment, the data may be addressed to a node other than the access point (not shown). In an embodiment (not shown), the data may also be broadcast or multi-cast. In one embodiment the data  335  may be sent using a preferred MCS indicated by the access point in the acknowledgement message. In the illustrated embodiment, after the data  335  is transmitted by the station, the access point  104  responds with an acknowledgement packet  340 . In an embodiment, the access point may transmit a CF-END frame (not shown) to end the transmission opportunity  315  after the STA  106  transmits the data  335 . 
     Note that while  FIG. 3A  shows the AP  104  transmitting a set of messages and the STA  106  transmitting a set of messages, one with skill in the art would recognize that in other embodiments, any type of node could transmit either set of messages. 
       FIG. 3B  is a timing diagram of one embodiment of a message exchange allocating a data communications medium between an access point and a station. In some aspects, the messages exchanged in  FIG. 3B  may be preceded by a negotiation between the AP and the STA defining whether a reverse direction grant request transmitted by the STA is supported. In some aspects, this negotiation may be performed via the exchange of management frames. The timing diagram starts at the left with a station (STA)  106  sending a reverse direction grant request message  305  to the access point. The reverse direction grant request message requests permission for the station to transmit data during a transmission opportunity of a second wireless device. 
     The access point then transmits an acknowledgement message  307  to the station acknowledging the RDG request message  305 . The acknowledgement message  307  may include an indication that permission to transmit during a transmission opportunity of the access point is granted. In an embodiment, the acknowledgment message  307  may also include a duration field, indicating a period of time for which the station has permission to transmit during a transmission opportunity of the access point. In an embodiment, the acknowledgement message  307  may include a delay field, indicating a period of time after which the access point expects the station to be able to transmit during the transmission opportunity of the access point. In an embodiment, the station may sleep for a time period based on the delay after receiving the acknowledgement message  307 . 
     In an embodiment, the acknowledgement message  307  may include a “more data” indication that is clear (“more data”=0). If permission to transmit during a second wireless device transmission opportunity is granted by the acknowledgement message  307 , a clear “more data” indication may indicate the STA  106  will receive a trigger frame from the AP  104  when it is allowed to transmit during an AP transmission opportunity. 
     The wireless medium then enters a contention period  311 . After the contention period  310 , a transmission opportunity of the access point  316  begins. During the transmission opportunity of the access point  316 , the access point  104  transmits a trigger frame  320  to the station  106 . In the illustrated embodiment, the trigger frame is a clear-to-send message. Alternatively, the access point  104  may send a QOS Null message to the station  106  as a trigger frame. In general the trigger frame can be any control, management or data frame. 
     Transmission of the trigger frame at the start of the transmission opportunity  316  is consistent with the “more data” indication being clear in the acknowledgement message  307 . The trigger frame  320  may include an indication that permission for the STA  106  to transmit during the transmission opportunity  316  is granted. In another embodiment, the two peer wireless devices may implicitly agree to grant a RDG to each other during association or with periodic management frames (e.g. beacons). An implicit agreement may provide the same or similar functions as the trigger frame  320 . 
     In some aspects, the two peer wireless devices may exchange management frames to define a periodic reverse direction grant of the TXOP of one device to the other device. In some aspects, this exchange of management frames may further define a duration of time of the periodic reverse direction grant or a duration of time between each reverse direction grant. In this aspect, an access point may transmit a reverse direction grant indication periodically at the agreed to times. A station may schedule itself to wake-up so as to receive the reverse direction grant from the access point and transmit uplink frames after the reverse direction grant is received as described further below. 
     The station then transmits data  336  during the transmission opportunity of the access point  316 . The data  336  may include one or more separate data packets. In an embodiment, the data  336  may be addressed to the access point (shown). In an embodiment, the data may be addressed to a node other than the access point (not shown). In an embodiment (not shown), the data may also be broadcast or multi-cast. In the illustrated embodiment, after the data  336  is transmitted by the station, the access point  104  responds with an acknowledgement packet  341 . In an embodiment, the access point may transmit a CF-END frame (not shown) to end the transmission opportunity  316  after the STA  106  transmits the data  336 . In another embodiment, the CF-END may also be sent if the STA is unresponsive for a time that exceeds SIFS time (+1 slot). 
     While  FIG. 3B  illustrates an access point  104  transmitting a first set of messages and station  106  transmitting a second set of messages, one with skill in the art would recognize that either an access point or a station could transmit either the first set and/or the second set of messages. 
     In one embodiment the ‘more data’ bit can be utilized by the access point (or in general the second wireless device) to indicate that a reverse direction grant will be granted. In such an embodiment, the AP (or in general the second wireless device) may set the more data bit in response to receiving a reverse direction grant request, such as request  305  (which may be a ps-poll or a trigger frame in one aspect). For example, the acknowledgement message  307  may have its more data bit set to 1. The AP may set the more data bit even if it has no downlink data buffered for the STA as shown in  FIG. 3B . In this embodiment, instead of sending the downlink buffered units after the contention period  311 , the AP can send a downlink frame (CF-Poll, Qos Null, CTS-to-Self, etc) which has the purpose of granting the remaining portion of the TXOP (or NAV) to the STA (or in general the first wireless device). The downlink frame may be sent after a time period based on a sleep duration field. The downlink frame initiates a packet exchange with the STA and sets the NAV to protect the STA&#39;s uplink transmission. In this embodiment, the downlink frame  320  is the initiator of the reverse direction grant. 
     In some aspects, the STA may not have any uplink data buffered to be transmitted to the access point. For example, this may occur when uplink data reaches its maximum lifetime. Alternatively, multiple scheduled reverse direction grants may be established between the AP and the STA, such that the STA may not always have enough data to fill each (potentially periodic) reverse direction grant from the access point. In some of these aspects, the STA may transmit a null data frame to indicate that it has no additional data to send. In response to receiving the null data frame, the access point may transmit one or more wireless messages to cancel any remaining reverse direction grant transmission opportunity to the station. 
     In other aspects, when the STA has no data available to transmit during a granted TXOP, the STA may not transmit any data during the granted TXOP. In response to not receiving any data from the STA, the AP may reset the NAV (or in other terms, free the TXOP) by transmitting a “CF-END” frame or alternatively a clear-to-send message to itself with a duration field set to zero. This can include a null data packet (NDP), clear-to-send, or clear to send to self. In some aspects, these messages include a bit indicating to receiving devices that they should reset their NAV (instead of setting the NAV). 
     In one aspects, a null data packet CTS may reset the NAV by including in a duration field a value equal to a NAV set by other STAs. In this aspect, a STA may transmit an NDP CTS (to self). This may set the NAV to all the STAs that successfully receive the NDP CTS) with a duration field set to a value indicating that the NAV lasts up to an indicated time T. Next, the same STA may transmit another NDP CTS (to self) to reset the NAV for all the STAs that successfully receive the second NDP CTS) by setting the duration field to a second value indicating a time interval up to the time T plus or minus a permitted delta to allow for errors. 
     A reverse direction grant may utilize any method that provides an implicit or explicit indication that the STA can transmit any type of frame SIFS time after receiving the downlink frame by the AP. Note that the method is applicable to any devices, not only between an AP and STA. 
       FIG. 3C  is a timing diagram of one embodiment of a message exchange  361  allocating a data communications medium between an access point and a station. In some aspects, the messages exchanged in  FIG. 3C  may be preceded by a negotiation between the AP and the STA defining whether a reverse direction grant request transmitted by the STA is supported. In some aspects, this negotiation may be performed via the exchange of management frames. The timing diagram starts at the left with a station (STA) sending a reverse direction grant request message  305  to the access point. The RDG request message  305  is acknowledged by acknowledgement message  307 . After the acknowledgement message is transmitted, the wireless medium enters a contention period  371 . During the contention period, the access point may transmit a request to send message  350 . The request to send message  350  may indicate a NAV period  370  for transmission of data by the AP  104 . 
     In response, the station may transmit a clear-to-send message  352 . In an embodiment, the clear-to-send message  352  may indicate a NAV period  365  that additionally indicates the period of time necessary for the station to send data it intends to send during a remaining portion of the NAV period, i.e., the NAV duration is extended to include the time necessary for the station to send its data. In another embodiment, the CTS frame may set a “more data” bit to indicate that it has data for the access point. After the clear-to-send message  352  is transmitted by the STA  106 , the wireless medium enters a contention free period  372 . The contention free period  372  may be based, at least in part, on the NAV period  365  indicated by the CTS message  352  transmitted by the station. 
     This contention free period  372  may correspond to a transmission opportunity of the access point  104 . The AP  104  may then transmit data packet  354 . The data packet  354  may also include a duration field consistent with the duration of the NAV  365  established by the CTS frame  352 . In some aspects, the AP  104  may precede transmission of the data packet  396  with a CTS frame (not shown) indicating the updated NAV  395 . For example, some aspects of data packet  396  may not include a duration field, and therefore it may be useful to first transmit a CTS frame with a duration field indicating the updated NAV. This may ensure that a device on the wireless network that is receiving transmissions of the AP  104  but not of the STA  106  recognizes the updated NAV value provided by the CTS frame  352 . 
     In the illustrated aspect, the data packet  354  is then acknowledged by the STA  106  with ACK message  356 . STA  106  may then send data packet  358  to the access point during the transmission opportunity of the access point. Note that data packet  358  is sent during the contention free period  372  that was extended relative to the NAV period  370  indicated by the request-to-send message  350 . The data message  358  is then acknowledged by the AP  104  with ACK message  360 . Thus,  FIG. 3A  shows that an RTS/CTS exchange between the AP  104  and STA  106  may extend the non-contention period of the wireless medium, for example, by indicating a NAV period, to ensure adequate time to transmit data by both the AP and the STA  106 . 
     In an embodiment, the AP  104  may deny the extension of the contention free period request by the station in the clear-to-send message  352 . For example, the AP  104  may ignore an updated NAV indicated in the clear-to-send message  352  and transmit a NAV value that was in effect prior to the transmission of the CTS message  352 . In an embodiment, the AP  104  may deny the extension of the contention free period by clearing a RDG/More PPDU bit in a packet transmitted after the CTS message  352  is received. 
     In a further embodiment, request-to-send message  350  may not be transmitted by the AP  104 , but the clear-to-send message  352  may still be transmitted by the STA  106 . In this embodiment, the clear-to-send message  352  may still indicate an indication of an increased NAV value as described above. 
     In this embodiment, after the CTS message is transmitted, the AP  104  may transmit a packet or message indicating the remaining NAV time period may be used by the station. This indication may be a reverse direction grant bit (RDG/more PPDU bit), or an implicit indication which can be performed by having the access point setting a larger NAV for its communications with the RTS and granting part of the NAV with the data packet. 
     In another embodiment, a request-to-send and clear-to-send exchange may occur without a preceding ps-poll/acknowledgement sequence. In this embodiment, a station that replies to a request-to-send with a clear-to-send message may include an indication in the clear-to-send message that extends the NAV time period to ensure enough time for the station to send data during a remaining transmission opportunity using the reverse direction protocol. In an embodiment, the indication in the clear-to-send message may extend the NAV period by using a more data bit. In an embodiment, other bits in the frame control portion of the clear-to-send message may be overloaded to provide the indication. 
     Table 1 below summarizes one embodiments use of indications in request and response messages transmitted on a wireless medium 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                 RDG 
                 RDG 
                 More 
                 Sleep 
                   
                   
               
               
                 Req 
                 Resp 
                 Data 
                 Duration 
                 AP Behavior 
                 STA Behavior 
               
               
                   
               
             
            
               
                 1 
                 0 
                 1 
                 S 
                 Transmit 
                 ACK Reception of 
               
               
                   
                   
                   
                   
                 downlink data 
                 downlink data, do 
               
               
                   
                   
                   
                   
                 SIFS (S) time 
                 not transmit uplink 
               
               
                   
                   
                   
                   
                 after 
                 data during 
               
               
                   
                   
                   
                   
                 acknowledgement 
                 transmit 
               
               
                   
                   
                   
                   
                   
                 opportunity 
               
               
                 1 
                 0 
                 0 
                 0 
                 AP has no data to 
                 Do not transmit 
               
               
                   
                   
                   
                   
                 transmit. Reverse 
                 during AP 
               
               
                   
                   
                   
                   
                 Direction Not 
                 transmission 
               
               
                   
                   
                   
                   
                 Granted 
                 opportunity 
               
               
                 1 
                 1 
                 1 
                 0 
                 Transmit 
                 Acknowledge 
               
               
                   
                   
                   
                   
                 downlink data 
                 reception of 
               
               
                   
                   
                   
                   
                 SIFS time after 
                 downlink data, use 
               
               
                   
                   
                   
                   
                 ack, Reverse 
                 reverse direction 
               
               
                   
                   
                   
                   
                 Direction granted 
                 grant for uplink 
               
               
                   
                   
                   
                   
                 to station. 
                 transmission. 
               
               
                 1 
                 1 
                 0 
                 0 
                 No data to 
                 Transmit uplink 
               
               
                   
                   
                   
                   
                 transmit, reverse 
                 data SIFS time 
               
               
                   
                   
                   
                   
                 direction not 
                 after 
               
               
                   
                   
                   
                   
                 granted to station 
                 acknowledgement. 
               
               
                 1 
                 0 
                 0 
                 S 
                 No data to 
                 Sleep for S ms, do 
               
               
                   
                   
                   
                   
                 transmit, no 
                 not transmit uplink 
               
               
                   
                   
                   
                   
                 reverse direction 
                 data during AP 
               
               
                   
                   
                   
                   
                 granted. 
                 transmit 
               
               
                   
                   
                   
                   
                   
                 opportunity 
               
               
                 1 
                 1 
                 1 
                 S 
                 Transmit 
                 Transmit 
               
               
                   
                   
                   
                   
                 downlink data S 
                 acknowledgement 
               
               
                   
                   
                   
                   
                 ms after 
                 of received 
               
               
                   
                   
                   
                   
                 acknowledgement, 
                 downlink data, use 
               
               
                   
                   
                   
                   
                 reverse direction 
                 remaining portion 
               
               
                   
                   
                   
                   
                 granted to station. 
                 of transmit 
               
               
                   
                   
                   
                   
                   
                 opportunity for 
               
               
                   
                   
                   
                   
                   
                 uplink 
               
               
                   
                   
                   
                   
                   
                 transmission. 
               
               
                 1 
                 1 
                 0 
                 S 
                 No data to 
                 Utilize reverse 
               
               
                   
                   
                   
                   
                 transmit, reverse 
                 direction grant 
               
               
                   
                   
                   
                   
                 direction granted 
                 indicated by 
               
               
                   
                   
                   
                   
                 to station. Access 
                 trigger frame for 
               
               
                   
                   
                   
                   
                 point may 
                 uplink 
               
               
                   
                   
                   
                   
                 transmit a trigger 
                 transmission. 
               
               
                   
                   
                   
                   
                 frame after S 
                   
               
               
                   
                   
                   
                   
                 duration of time 
               
               
                   
               
            
           
         
       
     
       FIG. 3D  shows a format of an exemplary request-to-send (RTS) frame  380 . The RTS frame  380  may be transmitted as part of some aspects of communication exchange  361  of  FIG. 3C . For example RTS  350  shown in communication exchange  361  may conform to the format of RTS frame  380 . 
     The RTS frame  380  includes a frame control field  382   a , as well as a duration/id field  382   b , receiver address field  382   c , transmitter address field  382   d  and frame check sequence (FCS) field  382   e . The frame control field  382   a  may be composed of multiple fields, including a protocol field  384   a , type field  384   b , sub-type field  384   c , toDS field  384   d , fromDS field  384   e , More Frag field  384   f , Retry field  384   g , Pwr Mgmt field  384   h , More Data field  384   i , Protected Frame field  384   j , and Order field  384   k.    
     In some aspects, the RTS frame  380  may indicate whether a receiving device has permission to extend a reverse direction grant NAV duration indicated by the duration/ID field  382   b  (as was shown by the transmission of CTS frame  352  in  FIG. 3C , which extended the NAV from a duration indicated by NAV  370  to a duration indicated by NAV  365 ). In some aspects, the order field  384   k  may be set to one to indicate that the transmitter of the RTS frame  380  allows a receiver of the RTS frame (for example, the TXOP responder) to extend the NAV and transmit during the extended portion of the NAV as illustrated in  FIG. 3C . In some other aspects, other fields of the RTS frame may be used to indicate whether permission is granted. (e.g., Retry bit, Protected frame field in the Frame Control field of the RTS). For example, other reserved fields or bits within the RTS frame  380  may be used to indicate whether permission to extend the NAV is granted. In one embodiment the permission to extend the NAV may be for the sole purpose of relaying a frame to a third device by the TXOP Responder. In some aspects, the order field  384   k  may be a relayed frame field in an 802.11ah standard. 
     In other aspects, whether permission to extend the NAV is granted to a TXOP responder may be communicated through the exchange of management frames that occurs before the RTS message (such as RTS message  350 ) is transmitted. 
       FIG. 3E-1  shows a format of an exemplary acknowledgment frame  385 . The acknowledgment frame  385  includes a frame control field  386   a , duration/id field  386   b  receiver address field  386   c , and a frame check sequence field  386   d . Similar to  FIG. 3D , the frame control field  386   a  includes a protocol field  387   a , type field  387   b , sub-type field  387   c , toDS field  387   d , fromDS field  387   e , More Frag field  387   f , Retry field  387   g , Pwr Mgmt field  387   h , More Data field  387   i , Protected Frame field  387   j , and Order field  387   k . In some aspects, the more data field  387   i  may be used to indicate that a transmitting device will utilize a remaining portion of a transmission opportunity as a TXOP requestor to transmit data to a device other than the TXOP owner. Such an embodiment is shown in  FIG. 3F  below. 
     In some embodiments, the acknowledgment may be a null data packet acknowledgement (NDP ACK) frame. A NDP acknowledgment frame (not shown) includes an NDP Type field, ACK ID field, Duration field, More Data field a Relayed Frame, and a CRC field. In such an embodiment the device transmitting the NDP Ack as a response to a received data frame from the TXOP holder, may indicate that it will use the remaining portion of the TXOP to transmit data to a device other than the TXOP owner. In one embodiment this may be indicated by having the relayed frame field of the NDP ACK set to 1. In some aspects, a TXOP owner may indicate permission for a second device to relay data during the TXOP by using the order field  387   k , as discussed below with respect to  FIGS. 3H-I  and  FIGS. 11A-12B . 
       FIG. 3E-2  shows an alternative format of the frame control field  386   a  of  FIG. 3E-1 . The frame control field format  389  of  FIG. 3E-2  includes a protocol field  388   a , type field  388   b , sub-type field  388   c , bandwidth indication field  388   d , dynamic indication field  388   f , Pwr Mgmt field  388   h , More Data field  388   i , Protected Frame field  388   j , and Order field  388   k . In some aspects, the more data field  388   i  may be used to indicate that a transmitting device will utilize a remaining portion of a transmission opportunity as a TXOP requestor to transmit data to a device other than the TXOP owner. In some aspects, a TXOP owner may indicate permission for a second device to relay data during the TXOP by using the order field  388   k , as discussed below with respect to  FIGS. 3H-I  and  FIGS. 11A-12B . 
       FIG. 3F  is a timing diagram of one embodiment of a message exchange  390  allocating a data communications medium between an access point and a station. While  FIG. 3F  illustrates an AP  104  as a TXOP owner and an STA  106   a  as a TXOP responder, one of skill in the art would recognize that in some aspects, an AP  104  may be a TXOP responder and a STA may be a TXOP owner. Alternatively, in other aspects, both the TXOP owner and TXOP responders may be stations (that may perform relay functionality). 
     Similar to message exchange  361  of  FIG. 3C , message exchange  390  illustrates a station  106   a  transmitting an RDG request message  391  to an AP  104 . The AP acknowledges the RDG Request message  391  with acknowledgement message  392 . The communications network illustrated in  FIG. 3F  then enters a contention period  397 . The AP  104  then transmits an RTS message  380 . A duration field in the RTS message  380  indicates a duration or NAV as shown by NAV  393 . This RTS message  380  may indicate whether a receiving device, such as STA  106   a , has permission to extend the NAV duration indicated by the RTS message  380  (as discussed above with respect to  FIG. 3D ). In the illustrated communication exchange, the RTS message  380  indicates the STA  106   a  does have permission to extend the NAV. STA  106   a  responds with a CTS  394 , which extends the NAV to a duration indicated by NAV  395 . The communications network of  FIG. 3F  then enters a non-contention period  398 . 
     The AP  104  then transmits data frame  396  to the STA  106   a . The data frame  396  may include a duration field indicating a NAV consistent with the updated NAV  395  indicated by the CTS frame  394 . In some aspects, the AP  104  may precede transmission of the data packet  396  with a CTS frame (not shown) indicating the updated NAV  395 . In one embodiment, the CTS frame in general may be a null data packet CTS (NDP CTS) (not shown). 
     In the illustrated embodiment, STA  106   a  acknowledges data frame  396  with acknowledgment packet  385 . As discussed above with respect to  FIG. 3E-1 , the acknowledgment packet  385  may indicate whether the STA  106   a  intends to transmit a frame to a 3 rd  device during the transmission opportunity  398 . In the illustrated example of  FIG. 3F , the acknowledgment packet  385  does indicate that the STA  106   a  will transmit data to a 3 rd  device during the transmission opportunity  398  of the AP  104 . For example, the STA  106   a  may indicate this via acknowledgment packet  385  by setting the more data field  387   i . In another embodiment (not shown) where the acknowledgement packet is an NDP acknowledgement frame, the STA  106   a  may provide the indication by setting a Relayed Frame bit included in the NDP ACK frame. 
     STA  106   a  then transmits data packet  399   a  to the STA  106   b . STA  106   b  acknowledges the data packet  399   a  with acknowledgement packet  399   b  during the transmission opportunity  398 . 
     While  FIG. 3F  illustrates the STA  106   a  indicating to the AP  104  in an acknowledgement packet  385  that it will transmit during the AP&#39;s transmission opportunity to a 3 rd  party device (namely, STA  106   b ), in some aspects, no indication is provided. In still other aspects, various other types of wireless message frames may be used to provide such an indication to a TXOP Owner such as AP  104 . For example, any frame a TXOP responder transmits to a TXOP owner may be used in alternate embodiments. Additionally, while  FIG. 3F  shows the TXOP responder (STA  106   a ) transmitting an acknowledgment packet  385  before transmitting data to the 3 rd  party device (STA  106   b ), in some aspects, the TXOP responder may transmit data to a 3 rd  party device SIFS time after a last frame is received from the TXOP owner by the TXOP responder. For example, in a variation of  FIG. 3F , the STA  106   a  may transmit the data frame  399   a  before the acknowledgement frame  385  in some aspects. 
       FIG. 3G  is a timing diagram of one embodiment of a message exchange  420  allocating a data communications medium between an access point and a station. While  FIG. 3G  illustrates an AP  104  as a TXOP owner and an STA  106   a  as a TXOP responder, one of skill in the art would recognize that in some aspects, an AP  104  may be a TXOP responder and a STA may be a TXOP owner. Alternatively, in other aspects, both the TXOP owner and TXOP responders may be stations (that may perform relay functionality). 
       FIG. 3G  first shows the STA  106  transmitting a PS-Poll frame  421 . The PS-Poll frame  421  includes a duration field. The value the STA  106  uses for the duration field may be based on the time for STA  106   a  to transmit one or more uplink data units to the AP  104  and/or an estimated time for the AP to transmit one or more downlink buffered units (BU&#39;s) to the STA  106   a . In the example of  FIG. 3G , a duration field in the PS-Poll frame  421  is set to the estimated time required for the STA  106   a  to transmit uplink data to the AP  104 , plus SIFS time, plus any time necessary to receive an acknowledgement from the AP  104 . This time is shown by NAV time period  422 . In some aspects, the duration/ID field of the RTS message  423  (and corresponding length of the NAV time period  422 ) may be based equations (1) or (2) below: 
         D=T   END-NAV   +T   PENDING   −T   PPDU   &lt;=D&lt;=T   TXOP     —     REMAINING   −T   PPDU   (1)
 
         D=T   END-NAV   +T   PENDING   −T   PPDU   &lt;=D   (2)
 
     where:
         T SINGLE-MSDU  is the estimated time required for the transmission of the allowed frame exchange sequence defined in 8.4.2.28 (EDCA Parameter Set element) (for a TXOP limit value of 0), including applicable IFSs (#156).   T PENDING  is the estimated time required for the transmission of
           Pending MPDUs of the same AC   Any associated immediate response frames   Any NDP transmissions and explicit feedback response frames   Applicable (#156) IFSs   Any RDG   
           T TXOP  is the value of dot11EDCATableTXOPLimit (dot11EDCAQAP-TableTXOPLimit for the AP) for that AC.   T TXOP-REMAINING  is T TXOP  less the time already used time within the TXOP.   T END-NAV  is the remaining duration of any NAV set by the TXOP holder, or 0 if no NAV has been established.   T PPDU  is the time required for transmission of the current PPDU.       

     In one aspect, the PS-Poll frame  421  indicates whether the AP  104  is allowed to respond with an RTS via a Response Indication field in the S1G field of the Physical Layer Convergence Protocol (PLCP) Preamble. In some aspects, if this field is set to “Long Response,” the AP  104  is allowed to extend the NAV period  422  indicated in the PS-Poll frame  421  via a request to send. In these aspects, if the Response Indication field in the SIG field is set to another value other than “Long Response,” the AP cannot extend the NAV set by the PS-Poll frame  421 . 
     Since the ps-poll frame  421  indicates the AP  104  is allowed to extend the NAV, upon reception of the PS-Poll frame  421  the AP  104  responds with a request-to-send (RTS) frame  423 . The AP  104  may transmit the RTS frame  423  after determining that the AP  104  has buffered units available for the STA  106   a . The RTS frame  423  may include a duration field equal to an amount of time indicated in the PS-Poll frame  421  plus any time needed for the AP to transmit downlink buffered units to the STA  106 . The duration field in the RTS frame  423  may also include additional time necessary for the eventual times, SIFS, and any additional acknowledgements transmitted by the STA  106   a . The NAV period requested by the RTS frame  423  is shown by NAV period  425 . A “More Data” field in the RTS frame  423  may be equal to one (1), indicating that a NAV extension is requested to transmit the downlink buffered units to the STA  106   a . Upon reception of the RTS frame  423 , the STA responds, after SIFS time, with a (NDP) CTS frame  426 . A duration field in the CTS frame  426  sets a NAV equal to the duration necessary to accommodate the NAV duration indicated by the RTS frame  423 . The NAV period set by the CTS frame  426  is shown as NAV  427 . Once the NAV period  427  is established, the AP  104  transmits downlink data  429 . The STA  106   a  acknowledges the data  429  with acknowledgement  430 , and then transmits uplink data  431 . The AP then acknowledges uplink data  431  with acknowledgment  432 . 
       FIG. 3H  is a timing diagram of one embodiment of a message exchange  3000  allocating a data communications medium between a two stations  106   a - b  and an access point  104 . While  FIG. 3H  illustrates the STA  106   a  as a TXOP owner and the AP  104  (relay) as a TXOP responder, one of skill in the art would recognize that in some aspects, a station  106  may be a TXOP responder and an AP may be a TXOP owner. Alternatively, in other aspects, both the TXOP owner and TXOP responders may be stations (that may perform relay functionality). 
     An S1G device that supports TXOP sharing may initiate a relay-shared TXOP by transmitting a S1G RTS frame with a relayed frame field (such as the order field  387   k  of  FIG. 3E-1  or the order field  388   k  of  FIG. 3E-2 ) set as a first frame in the exchange under Enhanced Distributed Channel Access (EDCA). A relay that receives the S1G RTS frame indicates whether it will utilize an explicit or implicit acknowledgment scheme during the relay-shared TXOP based in part by setting a response indication field in the S1G field of the PLCP Preamble or by setting the value of the Duration field of the response frame to a certain value as specified below. In certain embodiments the response frame is an NDP CTS frame. In some other aspects, the response frame is a CTS frame. 
     In some aspects, a relay can indicate explicit acknowledgments will be used by extending the NAV (relative to a NAV duration specified in the RTS frame) when transmitting the NDP CTS frame. When using implicit acknowledgement, a NDP CTS frame transmitted by the relay will not extend the NAV relative to that specified in the RTS frame. 
     In some other aspects, a non-NDP CTS frame will be transmitted in response to the RTS frame. This “regular” or non-NDP CTS may include a response indication field in its PLCP preamble that is set to “Long Response.” (Three (3) in some aspects) to indicate an explicit acknowledgment procedure will be used for relayed transmissions during the transmission opportunity. 
     If an explicit acknowledgement procedure will be utilized by the relay, the relay sets the duration field of the NDP CTS frame to a value D, where D is defined below: 
         D =min( T   RTS   +T   PENDING   −T   PPDU   ;T   TXOP     —     REMAINING   −T   PPDU )&lt;= D&lt;=T   TXOP     —     REMAINING   −T   PPDU , 
     Where:
         T RTS  is a value of the Duration/ID field of the S1G RTS frame that elicited the response,   T PPDU  is a time, in microseconds, between the end of the PPDU carrying the RTS frame and the end of the of the NDP CTS,   T PENDING  is an estimated time for the transmission of the frame to be forwarded and its response if required plus applicable IFS durations, and   T TXOP     —     REMAINING  is equal to any T TXOP  minus T RTS , where the TTXOP is the estimated amount of time of the current TXOP started by the TXOP initiator as known by the Relay.       

       FIG. 3H  first shows the STA  106   a  initiating a relay-shared TXOP by transmitting an S1G request-to-send message  3005 . In some aspects, instead of transmitting the request-to-send message  3005 , a short data frame may be transmitted. The STA  106   a  indicates its intent to start a relay-shared TXOP by setting a relayed frame field in a frame control field of the RTS message  3005 . In some aspects, the relayed frame field is the order field  387   k  of  FIG. 3E-1  or order field  388   k  of  FIG. 3E-2 . The relay  3005  may also indicate an initial NAV duration of the TXOP shown by NAV  3040 . 
     The AP  104  then responds with a null data packet (NDP) clear-to-send frame  3010 . If the AP  104  intends to use an explicit acknowledgement procedure, in some aspects, the relay will set the duration field of the CTS frame  3010  to indicate a relay-shared TXOP protection mechanism. For example, the duration field of the CTS frame will be set as described above. The CTS frame  3010  may also extend the duration of the NAV to protect any expected future relay transmissions (such as forwarding the expected Data frame  3015  to the STA  106   b  plus receiving any acknowledgments etc). This is shown by NAV duration  3050 . The STA  106   a  then transmits a data frame  3015 . 
     After receiving the data frame  3015 , and when using the explicit acknowledgement procedure, the relay AP  104  may set the NDP acknowledgment frame  3020  to have a response indication field in the S1G field of the PLCP Preamble to a value of “long response.” In addition, the relay may set the relayed frame field of the NDP acknowledgement frame  3020  to a first value (for example, one—shown). Otherwise, the relay shall signal a response indication of no response in the NDP acknowledgement frame  3020  by setting the relayed frame field to a second value (for example, “no response” or zero—not shown). 
     When using the explicit acknowledgment procedure, the relay  104  may forward the previously received short data frame  3015 , SIFS time after the relay transmitted the NDP acknowledgement frame  3020  to the STA  106   a . The relay  104  may further protect the forwarding of the data frame by preceding its transmission with an RTS/CTS exchange or by transmitting a CTS-to Self-frame with the STA  106   b . Upon successful receipt of the relayed short data frame  3025 , the STA  106   b  transmits an NDP acknowledgement frame  3030  to the relay  104 . This description may apply to both uplink and downlink procedures with the STA  106   a . For example, either the STA  106   a  or the AP  104  may be the TXOP owner in a TXOP sharing session. 
       FIG. 3I  is a timing diagram of one embodiment of a message exchange  3100  allocating a data communications medium between a two stations  106   a - b  and an access point  104 .  FIG. 3I  illustrates use of an implicit acknowledgement procedure with a relay-shared TXOP. While  FIG. 3I  illustrates the STA  106   a  as a TXOP owner and the AP  104  (relay) as a TXOP responder, one of skill in the art would recognize that in some aspects, a station  106  may be a TXOP responder and a AP may be a TXOP owner. Alternatively, in other aspects, both the TXOP owner and TXOP responders may be stations (that may perform relay functionality). 
     When an implicit acknowledgement procedure is utilized by a relay, it may set a response indication field of the S1G field of the PLCP Preamble in the response frame to an S1G RTS frame with the relayed frame set to 1 (e.g., the order field). to a value corresponding to “No response.” The response frame may be set in a CTS frame or a NDP CTS frame transmitted to the TXOP owner device. The duration/id field of the null data packet (NDP) clear-to-send (CTS) or CTS frame may be set to a value that is equal to the value of the Duration/ID field of the S1G RTS frame minus TPPDU as described above Upon successful reception by a relay of a short data frame  3115  from the TXOP owner, which is sent SIFS time after the transmission of the (NDP) CTS frame  3110  as described above, the relay may protect further transmission of the short data frame to a third device (to accomplish the relay) with a second RTS/CTS protection mechanism. A duration/ID field of a second RTS frame transmitted by the relay should be less than or equal to the maximum duration of a TXOP allocated for transmitting Short Data frames of the particular access category of Short Data frame  3115 . This access category is available in a PTID field of a frame control field of frame  3115  minus an estimated time since the beginning of reception of the first RTS frame (which had the relayed frame set to a first value (e.g. one) and was transmitted by the relay-shared TOP owner.  FIG. 3I  illustrates this message sequence. 
     Similar to  FIG. 3H , the message sequence using an implicit acknowledgement procedure also begins with a TXOP owner transmitting a S1G request-to-send (RTS) frame  3105  with the relayed frame set to 1 (e.g., the order bit set to 1) or Short data frame that includes a relayed frame field set to a first value (e.g. one). The RTS message  3105  indicates an initial NAV duration indicated by NAV  3140 . Because 31 illustrates use of an implicit acknowledgement procedure, the NDP CTS frame  3110  does not extend the NAV  3140  set by the RTS, as shown by NAV  3150 . The relay AP  104  responds with a null data packet (NDP) CTS frame  3110 . A duration field of the CTS frame  3110  is set as described above to indicate implicit acknowledgments will be used. 
     Upon receiving the CTS  3110 , the STA  106   a  may transmit a data frame  3115 . Because the relay  104  indicated implicit acknowledgments would be utilized via the duration field of the CTS frame  3110 , once the data  3115  is received by the relay, the relay  104  may protect the relay of data  3115  with RTS/CTS exchange  3120 / 3125 . If the STA  106   a  successfully receives at least part of the RTS frame  3020  (e.g., the PLCP header that includes the Partial AID information of the STA  106   b ) then it may recognize it as a successful acknowledgement of the data frame  3115   
     After the CTS frame  3125  is received by the relay, the relay  104  relays the data received as frame  3115  from the STA  106   a  (TXOP Owner in this example) to the STA  106   b  as data frame  3130 . The STA  106   b  may then acknowledgment the data frame  3130  using NDP acknowledgment frame  3135 . Note that the RTS frame  3020  sets a NAV  3141 , and the CTS  3125  confirms the NAV duration with NAV  3151 . 
       FIG. 4A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless communication network. In an embodiment, the first wireless device is a station and the second wireless device is an access point. In an embodiment, process  400  may be performed by an access point, such as access point  104 . In an embodiment, process  400  may be performed by wireless device  202 , illustrated in  FIG. 2 . In one aspect, process  400  may be performed by the AP  104  illustrated in  FIGS. 3A-C  to perform the AP  104 &#39;s respective portions of the wireless communication exchanges shown in those figures. 
     In processing block  405 , a request from a first wireless device for permission to transmit during a transmission opportunity of a second wireless device is received. In an embodiment, the request for permission may be included as part of a ps-poll request or any type of trigger frame. In an embodiment, the request for permission may specify a duration of time for which permission to transmit is requested. I 
     In block  410  a message is transmitted to the first wireless device granting permission to transmit during a second wireless device transmission opportunity in response to the request. In an embodiment, the message may specify a duration of time for which permission to transmit is granted. In an embodiment, the message may specify a delay time period. In an embodiment, after the delay time period, the first wireless device may expect a frame that activates a reverse direction grant or grants permission to transmit data during a transmission opportunity of the second wireless device. In some embodiments, the first wireless device may sleep for a time based on the delay time period after receiving the transmitted message. In an embodiment, the transmitted message may be an acknowledgement message. In an embodiment, the transmitted message may be a clear-to-send message or a QOS Null message. In an embodiment, the transmitted message may be a data message. The data message may include data or may be a null data message and include no data payload. In some other aspects, the message granting permission may be an acknowledgement message. 
     The transmitted message may include a “more data” indication. The “more data” indication may indicate whether the second wireless device will send data to the first wireless device before the first wireless device may transmit data during a second wireless device transmission opportunity. In some aspects, if the more data indication is set, process  400  includes transmitting a downlink frame after transmission of the more data indication. In these aspects, the downlink frame indicates that the first wireless device may now transmit during the transmission opportunity of the second wireless device. 
     In an embodiment, if the “more data” indication is not set, the second wireless device may transmit a second message indicating the first wireless device may begin transmitting during a second wireless device transmission opportunity. In an embodiment, this second message may be a trigger frame. For example, the second message may be a clear-to-send message. In this embodiment, the clear to send message grants permission for the first wireless device to transmit in the transmission opportunity of the second wireless device. 
     In an embodiment, if the “more data” indication is set, then the second wireless device may transmit a different second message indicating the first wireless device may begin transmitting during a second wireless device transmission opportunity. In an embodiment, the different second message may be a data message. The data message may also include an indication that the first wireless device may begin transmitting data in a transmission opportunity of the access point. This indication may be a reverse direction grant indication. 
     In some aspects, process  400  may include periodically transmitting a reverse direction grant indication to the first wireless device. In some aspects, process  400  may include periodically transmitting a beacon message indicating one or more transmission opportunities of the second wireless device. 
     After permission is granted to the first wireless device to transmit during a transmission opportunity, process  400  may further include receiving data from the first wireless device. Before data is received, in some aspects, process  400  may include transmitting a message during the transmission opportunity. For example, the second wireless device may grant permission for the first wireless device to transmit only within a later portion of a transmission opportunity. The second wireless device may use an earlier portion of the transmission opportunity for its own purposes. 
     In some aspects, process  400  further includes transmitting a message canceling a previously granted permission to transmit during a transmission opportunity. In some aspects, this message is a CF-END message. 
     In some aspects, process  400  further includes receiving a clear to send message. The clear to send message indicates a request for extension of a contention free time period on the wireless medium. In response, some aspects include transmitting a request to send message indicating a second contention free period on the wireless medium. The second contention free period is different than the first contention free period. Some aspects further include transmitting a message on the wireless medium indicating a contention free period on the wireless medium different than the first contention free period in response to receiving the clear to send message. 
       FIG. 4B  is a functional block diagram of an exemplary device  450  that may be employed within the wireless communication system  100 . The device  450  includes means for receiving a request from a first wireless device for permission to transmit during a transmission opportunity of a second wireless device. In an embodiment, means  455  may be configured to perform one or more of the functions discussed above with respect to block  405 . In an embodiment, the means for receiving a request from a first wireless device for permission to transmit during a transmission opportunity of a second wireless device may include a receiver, such as receiver  212  of  FIG. 2 . Means  455  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  450  further includes means  460  for transmitting a message to the first wireless device granting permission to transmit during a transmission opportunity of the second wireless device in response to the request. In an embodiment, means  460  may be configured to perform one or more of the functions discussed above with respect to block  410 . The means  460  for transmitting a message to the first wireless device granting permission to transmit during a transmission opportunity of the second wireless device in response to the request may include a transmitter, such as transmitter  210  of  FIG. 2 . Means  460  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
       FIG. 5A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless communication network. In an embodiment, process  500  may be performed by a station, such as station  106 . In an embodiment, the first wireless device is a station and the second wireless device is an access point. In another embodiment, the first wireless device is an access point and the second wireless device is a station. In an embodiment, process  500  may be performed by wireless device  202 , illustrated in  FIG. 2 . In one aspect, process  500  may be performed by the STA  106  illustrated in  FIGS. 3A-C  to perform the STA  106 &#39;s respective portions of the wireless communication exchanges shown in those figures. 
     In processing block  505 , a first wireless device transmits a request to a second wireless device for permission to transmit data during a transmission opportunity of the second wireless device. In an embodiment, the first wireless device may be a station. In an embodiment, the request for permission may be included as part of a ps-poll request or any trigger frame. In these aspects, process  500  may include transmitting the ps-poll request or any trigger frame comprising the request for permission to transmit. In an embodiment, the request for permission may specify a requested duration of transmission time. The duration may be an indication of the length of time for which permission to transmit data is requested. In one aspect, the request may further indicate a time period for which permission to transmit is requested. For example, the request may indicate a time period relative to a next or other beacon interval. 
     In block  510 , a message is received granting permission to transmit the data during a transmission opportunity of the second wireless device. In an embodiment, the message may specify a duration of time for which permission to transmit is granted. In some aspects, the received message may include an indication of a length of time after which permission to transmit in a transmission opportunity of the second wireless device will be granted. 
     In an embodiment, process  500  may include receiving an indication of a delay time period as part of the message granting permission. In an embodiment, after the received delay time period, the first wireless device may expect a frame that activates a reverse direction grant, or grants permission to transmit data during a transmit opportunity of the second wireless device. In some embodiments, the first wireless device may enter a sleep state in response to receiving the message. The first wireless device may sleep for a time period based on the delay time period. For example, the first wireless device may sleep for a time period less than or equal to the delay time period indicated in the message. 
     In an embodiment, the received message may be an acknowledgement message. In an embodiment, the received message may be a data packet. The data packet may include data or may be a null data message. In an embodiment, the received message may be a clear-to-send message. 
     In some aspects, the received message may include a more data indication. If the more data indication is set, process  500  may further include receiving data from the second wireless device, the received data indicating that permission to transmit during the transmission opportunity has now been granted. In some aspects, the received data is a downlink frame. In response to receiving the data, process  500  may transmit data during the transmission opportunity of the second wireless device. 
     Some aspects of process  500  include transmitting data during a transmission opportunity of the second wireless device, based at least in part on the message received that grants permission to transmit. In some aspects, the data is transmitted to a device or node on the wireless network that is not the second wireless device, but is still transmitted during a transmission opportunity of the second wireless device. 
     Some aspects of process  500  further include transmitting a clear to send message. The clear to send message requests an extension of a contention free time period on the wireless medium. In some aspects, the contention free time period is a transmission opportunity of the second wireless device. In some aspects, the clear to send message includes an indication of the contention free time period. For example, the clear to send message may indicate the contention free time period based on a time reference relative to a beacon interval. 
     Some aspects of process  500  further include receiving a message indicating a contention free period on the wireless medium different than the first content free period. In some aspects, this message is received in response to the transmission of the clear to send message. In some aspects, this message is a request to send message. 
     Some aspects of process  500  further include periodically receiving a reverse direction grant indication from the second wireless device. 
       FIG. 5B  is a functional block diagram of an exemplary device  550  that may be employed within the wireless communication system  100 . The device  550  includes means  555  for transmitting a request to a second wireless device for permission to transmit data during a transmission opportunity of the second wireless device. In an embodiment, means  555  may be configured to perform one or more of the functions discussed above with respect to block  505 . The means  555  for transmitting a request to a second wireless device for permission to transmit data during a transmission opportunity of the second wireless device may include a transmitter, such as transmitter  212  of  FIG. 2 . Means  555  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  550  further includes means  560  for receiving a message granting permission to transmit the data during a transmission opportunity of the second wireless device. In an embodiment, means  560  may be configured to perform one or more of the functions discussed above with respect to block  510 . In an embodiment, the means for receiving a message granting permission to transmit the data during a transmission opportunity of the second wireless device may include a receiver, such as receiver  212  of  FIG. 2 . Means  560  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
       FIG. 6A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless communication network. In an embodiment, process  600  may be performed by a station, such as station  106 . In an embodiment, the first wireless device is a station and the second wireless device is an access point. In another embodiment, the first wireless device is an access point and the second wireless device is a station. In an embodiment, process  600  may be performed by wireless device  202 , illustrated in  FIG. 2 . In one aspect, process  600  may be performed by the STA  106  illustrated in  FIGS. 3A-C  or  3 F-G to perform at least a portion of AP  104 &#39;s respective portions of the wireless communication exchanges shown in the figures. In some aspects, process  600  may be performed by the STA  106   a  of  FIG. 3H  and/or  FIG. 3I . 
     In block  605 , a first message is transmitted by a first wireless device. The first message indicates an initial duration of a transmission opportunity of the first wireless device. In some aspects, the first message is generated as a request-to-send message. In some aspects, the first message is generated as a PS-Poll frame or as a trigger frame. In some of these aspects, the initial duration may be indicated by a duration/ID field, such as field  382   b  shown in  FIG. 3D . In some aspects, a first timer (e.g., NAV counter) is initiated at the receivers of the frame based on the duration value included in the frame. The first counter may count down at a uniform rate. 
     In some aspects, block  605  includes generating the first message to indicate whether the first device grants permission to utilize at least a portion of the transmission opportunity to relay data transmitted by the first device. In some aspects, the permission is indicated in a frame control field of the first message. Specifically, in some of these aspects, the permission is indicated in an order field or a relayed frame field of the first message. 
     In block  610 , a second message is received. In some aspects, the second message is a response to the first message. The second message may be received SIFS time after transmission of the first message is complete in some aspects. 
     The second message is then decoded in block  615  to determine a new duration of the transmission opportunity. In some aspects, the second message is decoded as a clear-to-send message. In some aspects the second message is a request-to-send message. In some aspects, the new duration is decoded to be longer than the duration indicated in the first message. In some aspects, upon decoding the new duration, the first device initiates a second timer (e.g. NAV counter) at the receiver STAs that receive this frame. The second timer may also count down at a uniform rate. 
     In some aspects, the second message is further decoded to determine whether an explicit or implicit acknowledgment procedure will be used for relayed data during the transmission opportunity. This decoding may be conditional on whether the first device granted permission to relay data during the transmission opportunity, as discussed above with respect to block  605 . In some aspects, a response indication field in a PLCP header of the second message may be decoded to determine the acknowledgment procedure, as discussed above with respect to  FIGS. 3H-3I . In some aspects, the explicit or implicit acknowledgment procedure will be determined based on whether the second message updates a network allocation vector (NAV). For example, if the second message leaves the NAV unchanged, an implicit acknowledgment procedure will be used, whereas if the second message extends the duration of the NAV, explicit acknowledgments will be utilized. Once the acknowledgment procedure is determined, whether data transmitted has been acknowledged will be based on the determined acknowledgment procedure. 
     Some aspects of process  600  further include transmitting a third message indicating whether a second device has permission to extend the duration of the transmission opportunity. In certain aspects, the permission to extend the duration of the transmission opportunity is indicated by a duration field included in the third message. If the duration field in the third message points to the instant of the expiration of the first timer, a permission to extend the duration is not allowed and the second wireless device shall update the duration fields of the frames transmitted in the same TXOP based on the duration indicated by the first wireless device. If the value of the duration field points to the instant of the expiration of the second timer, a permission to extend the duration is allowed and both wireless devices shall update the duration fields of the frames that follow, transmitted in that same TXOP, based on the duration indicated by the second wireless device. 
     In some aspects, the permission to extend the duration of the transmission opportunity is indicated by the transmission of the third message itself. If the second device replies with the third message, after a given amount of time (e.g., SIFS time) it is an indication of permission to transmit. Failure to receive the third message is an indication for the second device that it is not allowed to extend the duration of the transmission opportunity. In some aspects, the first message and the third message are the same message. In some aspects, the third message is a clear-to send message. In certain aspects the clear to send message may be of null data packet type. For example, as shown in  FIG. 3F , a device, such as the AP  104  of  FIG. 3F , may transmit a request to send message such as request to send message  380 . This message may indicate, via an order field in a frame control field or other field, whether permission to extend the duration indicated by the request-to-send is permitted by a receiving device, which may be specified in the receiving address field  382   c  of request-to-send message  380  in some aspects. In some aspects, setting the order bit in the frame control field, or setting another reserved field in the request-to-send frame  380  may provide the indication that permission is granted. In some aspects that do not utilize a request-to-send frame, any bit or series of bits may be used to provide such an indication. 
       FIG. 6B  is a functional block diagram of an exemplary device  650  that may be employed within the wireless communication system  100 . The device  650  includes means  655  for transmitting a first message, the first message indicating an initial duration of a transmission opportunity. In an embodiment, means  655  may be configured to perform one or more of the functions discussed above with respect to block  605 . The means for transmitting 655 may include a transmitter, such as transmitter  210  of  FIG. 2 . Means  655  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  650  further includes means  660  for receiving a second message. In an embodiment, means  660  may be configured to perform one or more of the functions discussed above with respect to block  610 . In an embodiment, the means for receiving 660 may include a receiver, such as receiver  212  of  FIG. 2 . Means  660  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  650  further includes means  665  for decoding the second message to determine a new duration of the transmission opportunity. In an embodiment, means  665  may be configured to perform one or more of the functions discussed above with respect to block  615 . In an embodiment, the means for receiving 665 may include a processor, such as processor  204  of  FIG. 2 . Means  665  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     Some aspects of process  600  may include process  1200 , discussed below with respect to  FIG. 12A . For example, in some aspects, the first message of process  600  and the first message of process  1200  are equivalent. 
       FIG. 7A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless communication network. In an embodiment, process  700  may be performed by a station, such as station  106 . In an embodiment, the first wireless device is a station and the second wireless device is an access point. In another embodiment, the first wireless device is an access point and the second wireless device is a station. In another embodiment, both the first wireless device and the second wireless device are stations. In some aspects, the first device is a TXOP responder while the second wireless device is a TXOP owner. 
     In an embodiment, process  700  may be performed by wireless device  202 , illustrated in  FIG. 2 . In one aspect, process  700  may be performed by the STA  106  illustrated in  FIGS. 3A-C  or  3 F or  3 G to perform at least a portion of STA  106 ( a )&#39;s respective portions of the wireless communication exchanges shown in the figures. In some aspects, process  700  may be performed by the AP  104  (relay) described with respect to  FIG. 3H  and/or  FIG. 3I . 
     In block  705 , a first message is received by a first device. In block  710 , the first message is decoded to determine a duration of a transmission opportunity of a second device. For example, in some aspects, the first message is decoded as a request-to-send message, which may include a duration/ID field, such as duration/ID field  382   b  in request-to-send frame  380 . The duration/ID field may indicate the duration of a transmission opportunity. 
     In block  715 , a second message is generated via the first device. In some aspects, the second message is generated as a clear-to-send message. The second message is generated to indicate a new duration of the transmission opportunity. In some aspects, a device performing process  700  may have an amount of data to transmit that is greater than the duration indicated in the first message. To ensure NAV protection for a larger portion of data the first device may have available for transmission, the first device may generate the second message as described in block  715 . 
     When transmitted to a TXOP Owner, the second message may extend the NAV of a wireless network and ensure a data transmission longer than the duration indicated in the first message can be completed successfully with adequate protection from collisions. Generally therefore, if a device performing process  700  determines the NAV needs to be extended, the new duration will be greater than the original duration indicated in the first message. 
     In some aspects, the indicated new duration of block  715  may be determined based on either equation (1) or (2) described above and reproduced below: 
         D=T   END-NAV   +T   PENDING   −T   PPDU   &lt;=D&lt;=T   TXOP     —     REMAINING   −T   PPDU   (1)
 
         D=T   END-NAV   +T   PENDING   −T   PPDU   &lt;=D   (2)
 
     where:
         T SINGLE-MSDU  is the estimated time required for the transmission of the allowed frame exchange sequence defined in 8.4.2.28 (EDCA Parameter Set element) (for a TXOP limit value of 0), including applicable IFSs (#156).   T PENDING  is the estimated time required for the transmission of
           Pending MPDUs of the same AC   Any associated immediate response frames   Any NDP transmissions and explicit feedback response frames   Applicable (#156) IFSs   Any RDG   
           T TXOP  is the value of dot11EDCATableTXOPLimit (dot11EDCAQAP-TableTXOPLimit for the AP) for that AC.   T TXOP-REMAINING  is T TXOP  less the time already used time within the TXOP.   T END-NAV  is the remaining duration of any NAV set by the TXOP holder, or 0 if no NAV has been established.   T PPDU  is the time required for transmission of the current PPDU.       

     In block  720 , the second message is transmitted on the wireless network. 
     Some aspects of process  700  further include receiving a third message, and decoding the third message to determine whether the device performing process  700  has permission to extend the duration of the transmission opportunity of the second device. In some aspects, the third message is the first message. In these aspects, if the third message indicates the device performing process  700  does not have permission to extend the NAV or duration, then process  700  may not perform blocks  715  or  720  in these aspects. 
     In some aspects, values of duration fields (if any) of frames transmitted by the TXOP owner or the TXOP responder within a TXOP indicate that the NAV expires at the same instant of time as previously indicated by another duration field in a previously transmitted frame within the same TXOP. Frames transmitted during a TXOP that do not include a duration field do not affect the duration of a current NAV. 
     Some aspects of process  700  further include decoding the first message to determine whether permission is granted to relay data transmitted by the second device during the transmission opportunity. For example, in some aspects, the first message of process  700  is equivalent to the first message of process  1100 , discussed below. In some of these aspects, the second message is further generated to indicate an acknowledgment procedure for data relayed during the transmission opportunity. For example, in some aspects, the second message is a non-NDP CTS message. In these aspects, a response indication field of a S1G PLCP header of the second message may indicate the acknowledgment procedure. In some aspects, an explicit acknowledgment procedure may be indicated by generating the response indication field to have a first value. In some aspects, an implicit acknowledgment procedure may be indicated by generating the response indication field to have a second value. 
     In some aspects, the second message may be a null data packet CTS message, such as NDP CTS message  3010  of  FIG. 3H  or  3110  of  FIG. 3I . If explicit acknowledgments are used, a duration field of the second message may extend a NAV defined by the first message. In some aspects, the duration field is based on an estimated time for transmission of a frame to be relayed and a corresponding response if the acknowledgment procedure indicates an explicit acknowledgment procedure. The duration field may be set in substantial conformance to the discussion of  FIG. 3H  above. If implicit acknowledgments are used, the duration field may be set in substantial conformance with the discussion of  FIG. 3I , discussed above. For example, the duration field of the second message may not extend a NAV duration defined by the first message when implicit acknowledgments are used. 
     In relaying aspects of process  700 , process  700  further includes receiving data from the second device; and acknowledging the data based on the indicated acknowledgment procedure. If an explicit acknowledgment procedure is in use, process  700  further includes transmitting a null data packet acknowledgement frame to the second device in response to receiving the data, as discussed above with respect to  FIG. 3H . 
     If implicit acknowledgments are being used, process  700  further includes transmitting a request-to-send message to a third device in response to receiving the data, as discussed above with respect to  FIG. 3I . When explicit acknowledgements are used, process  700  may also include transmitting a request to send message to a third device. For example, the RTS message may be transmitted SIPS time after the NDP acknowledgement, such as NDP acknowledgment  3020  of  FIG. 3H . 
     Some implementations may combine process  700  with process  1100 , discussed below with respect to  FIG. 11A . For example, the first message of process  700  may be the same message as the first message of process  1100 . Additionally, the second message of process  700  may be equivalent to the response message discussed with respect to process  1100 . 
       FIG. 7B  is a functional block diagram of an exemplary device  750  that may be employed within the wireless communication system  100 . The device  750  includes means  755  for receiving a first message. In an embodiment, means  755  may be configured to perform one or more of the functions discussed above with respect to block  705 . The means for receiving 755 may include a receiver, such as receiver  212  of  FIG. 2 . Means  755  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  750  further includes means  760  for decoding the first message to determine a duration of a transmission opportunity of a second device. In an embodiment, means  760  may be configured to perform one or more of the functions discussed above with respect to block  710 . In an embodiment, the means for decoding  760  may include a processor, such as processor  204  of  FIG. 2 . Means  760  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  750  further includes means  765  for generating a second message, the second message indicating a new duration of the transmission opportunity. In an embodiment, means  765  may be configured to perform one or more of the functions discussed above with respect to block  715 . In an embodiment, the means for generating 765 may include a processor, such as processor  204  of  FIG. 2 . Means  765  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  750  further includes means  770  for transmitting the second message. In an embodiment, means  770  may be configured to perform one or more of the functions discussed above with respect to block  720 . In an embodiment, the means for transmitting 770 may include a transmitter, such as transmitter  210  of  FIG. 2 . Means  770  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
       FIG. 8A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless communication network. In an embodiment, process  800  may be performed by a station, such as station  106 . In an embodiment, the first wireless device is a station and the second wireless device is an access point. In another embodiment, the first wireless device is an access point and the second wireless device is a station. In another embodiment, both the first wireless device and the second wireless device are stations. In some aspects, the first wireless device is a TXOP responder while the second wireless device is a TXOP owner. 
     In an embodiment, process  800  may be performed by wireless device  202 , illustrated in  FIG. 2 . In one aspect, process  800  may be performed by the STA  106   a  illustrated in  FIG. 3F  to perform at least a portion of STA  106 ( a )&#39;s wireless communication exchanges shown in the figures. 
     In block  805 , a message is received via a first wireless device. In block  810 , the first message is decoded to determine that permission is granted to transmit data during a transmission opportunity of a second wireless device. In some aspects, the first message may be part of a reverse direction grant as described previously. In some aspects, the first message is decoded as a request-to-send message. In block  815 , data is transmitted by the first wireless device to a third wireless device during the transmission opportunity. The third wireless device is different than the second wireless device. As demonstrated in  FIG. 3F , a TXOP responder may transmit data to a 3 rd  device, such as STA  106   b  in  FIG. 3F , during a transmission opportunity of a second device, or TXOP owner. In the case of  FIG. 3F , the TXOP owner is of course the AP  104 . 
     Some aspects of process  800  further include generating and transmitting a third message indicating the first device will transmit data to a device other than the second device. In some aspects, the third message is generated as a data or acknowledgment message. In some aspects, process  800  includes setting a more data field, or a relayed frame bit in a NDP acknowledgment frame or in a data message or other message to provide the indication. 
       FIG. 8B  is a functional block diagram of an exemplary device  850  that may be employed within the wireless communication system  100 . The device  850  includes means  855  for receiving a first message. In an embodiment, means  855  may be configured to perform one or more of the functions discussed above with respect to block  805 . The means for receiving 855 may include a receiver, such as receiver  212  of  FIG. 2 . Means  855  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  850  further includes means  860  for decoding the first message to determine permission is granted to transmit data during a transmission opportunity of a second device. In an embodiment, means  860  may be configured to perform one or more of the functions discussed above with respect to block  810 . In an embodiment, the means for decoding  860  may include a processor, such as processor  204  of  FIG. 2 . Means  860  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  850  further includes means  865  for transmitting data to a third device different than the second device during the transmission opportunity. In an embodiment, means  865  may be configured to perform one or more of the functions discussed above with respect to block  815 . In an embodiment, the means for transmitting 865 may include a transmitter, such as transmitter  210  of  FIG. 2 . Means  865  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
       FIG. 9A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless communication network. In an embodiment, process  900  may be performed by a station, such as station  106 . In an embodiment, the first wireless device is a station and the second wireless device is an access point. In another embodiment, the first wireless device is an access point and the second wireless device is a station. In another embodiment, both the first wireless device and the second wireless device are stations. In some aspects, the first wireless device is a TXOP responder while the second wireless device is a TXOP owner. 
     In an embodiment, process  900  may be performed by wireless device  202 , illustrated in  FIG. 2 . In one aspect, process  900  may be performed by the STA  106   a  illustrated in  FIG. 3F  to perform at least a portion of STA  106   a &#39;s wireless communication exchanges shown in the figures. 
     In block  905 , a first message is received by a first wireless device. In block  910 , the first wireless message is decoded to determine permission has been granted to transmit data during a transmission opportunity of a second wireless device. 
     In block  910 , a second message is generated by first device, the message is generated to indicate data will be transmitted to a third wireless device during the transmission opportunity. 
     In block  915 , a second message is generated to indicate the data will be transmitted to a third device during the transmission opportunity. The third wireless device is different than the second wireless device. As shown in  FIG. 3F , a TXOP responder may transmit an indication to a TXOP owner that it intends to transmit data to a 3 rd  device, such as STA  106   b , during the TXOP owner&#39;s transmission opportunity. 
     In block  920 , the second message is transmitted on the wireless network. In some aspects, the second message is generated as a data or acknowledgment message. In some aspects, process  900  includes setting a more data field, or a relayed frame field in a NDP acknowledgment, or in a data message to provide the indication. Process  900  may also include transmitting the data to the third wireless device. 
       FIG. 9B  is a functional block diagram of an exemplary device  950  that may be employed within the wireless communication system  100 . The device  950  includes means  955  for receiving a first message. In an embodiment, means  955  may be configured to perform one or more of the functions discussed above with respect to block  905 . The means for receiving 955 may include a receiver, such as receiver  212  of  FIG. 2 . Means  955  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  950  further includes means  960  for decoding the first message to determine permission is granted to transmit data during a transmission opportunity of a second device. In an embodiment, means  960  may be configured to perform one or more of the functions discussed above with respect to block  910 . In an embodiment, the means for decoding  960  may include a processor, such as processor  204  of  FIG. 2 . Means  960  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  950  further includes means  965  for generating a second message indicating the data will be transmitted to a third device during the transmission opportunity, the third device different than the second device. In an embodiment, means  965  may be configured to perform one or more of the functions discussed above with respect to block  915 . In an embodiment, the means for generating 965 may include a processor, such as processor  204  of  FIG. 2 . Means  965  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  950  further includes means  970  for transmitting the second message. In an embodiment, means  970  may be configured to perform one or more of the functions discussed above with respect to block  920 . In an embodiment, the means for transmitting 965 may include a transmitter, such as transmitter  210  of  FIG. 2 . Means  970  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
       FIG. 10A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless communication network. In an embodiment, process  1000  may be performed by a station, such as station  106 . In an embodiment, the first wireless device is a station and the second wireless device is an access point. In another embodiment, the first wireless device is an access point and the second wireless device is a station. In another embodiment, both the first wireless device and the second wireless device are stations. In some aspects, the first wireless device is a TXOP owner while the second wireless device is a TXOP responder. 
     In block  1005 , a first message is transmitted by a first device. The first message grants permission to a second device to transmit data during a transmission opportunity of the first device. In block  1010 , a second message is received by the first device. 
     In block  1015 , the second message is decoded to determine that the data will be transmitted by the second device to a third device during the transmission opportunity. The third device is different than the first device. In some aspects, the second message is decoded as a data or an acknowledgment message. In some aspects, process  1000  includes decoding a more data field or a relayed frame field of the second message to determine that the data will be transmitted by the second device to a third device during the transmission opportunity. 
       FIG. 10B  is a functional block diagram of an exemplary device  1050  that may be employed within the wireless communication system  100 . The device  1050  includes means  1055  for transmitting a message granting permission to a second device to transmit data during a transmission opportunity of a first device. In an embodiment, means  1055  may be configured to perform one or more of the functions discussed above with respect to block  1005 . In an embodiment, the means for transmitting 1055 may include a transmitter, such as transmitter  210  of  FIG. 2 . Means  1055  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  1050  further includes means  1060  for receiving a second message. In an embodiment, means  1060  may be configured to perform one or more of the functions discussed above with respect to block  1010 . The means for receiving 1060 may include a receiver, such as receiver  212  of  FIG. 2 . Means  1060  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  1050  further includes means  1065  for decoding the first message to determine the data will be transmitted by the second device to a third device during the transmission opportunity of the first device, wherein the third device is different than the first device. In an embodiment, means  1065  may be configured to perform one or more of the functions discussed above with respect to block  1015 . In an embodiment, the means for decoding  1065  may include a processor, such as processor  204  of  FIG. 2 . Means  1065  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
       FIG. 11A  is a flowchart of a process for allocating a data communications medium between a first and second wireless device on a wireless communication network. In an embodiment, process  1100  may be performed by a station, such as station  106 . In an embodiment, the first wireless device is a station and the second wireless device is an access point. In another embodiment, the first wireless device is an access point and the second wireless device is a station. In another embodiment, both the first wireless device and the second wireless device are stations. In some aspects, the second wireless device is a TXOP owner while the first wireless device is a TXOP responder. In some aspects, process  1100  is performed by the AP relay  104  in  FIG. 3H . In some other aspects, process  1100  is performed by the AP relay  104  in  FIG. 3I . 
     In block  1105 , a first message is received by a first wireless device. The first message is from a second device. For example, the first message may be a request-to-send message, such as request-to-send message  3005  of  FIG. 3H . In some aspects, the first message of block  1105  is the first message of process  600 , discussed with respect to  FIG. 6A , the first message of process  700  described with respect to  FIG. 7A , the first message of process  800 , described with respect to  FIG. 8A , and/or the first message of process  900  discussed with respect to  FIG. 9A , 
     In block  1110 , the first message is decoded to determine whether permission is granted to the first device to utilize at least a portion of a transmission opportunity of the second device to relay data transmitted by the second device. For example, referring back to  FIG. 3H , the transmission opportunity may be for the STA  106   a . In other words, the STA  106   a  (or the second device in process  1100 ) may be the TXOP owner. Permission may be indicated in some aspects, by the order field  387   k  of the first message, discussed with respect to  FIG. 3E-1 , or order field  388   k  of  FIG. 3E-2 . For example, if the order field has a value of one (1), it may indicate permission is granted. If the value is zero, it may indicate the second device is not providing use of its TXOP for relay purposes. The order field  387   k  may also be referred to as a relayed frame field in some aspects. 
     In block  1115 , a response to the first message is generated. The response is generated to indicate an acknowledgment procedure for data that may be relayed by the first wireless device or to indicate intention to use the granted TXOP. The acknowledgment procedure may define whether explicit or implicit acknowledgments are used for the relayed data. 
     The acknowledgment procedure may be indicated in some aspects by a response indication field in a S1G field of the PLCP Preamble of the response, which, in some aspects, is a clear to send message. If the response indication is set to a value of “long response” (three (3) in some aspects), the response may indicate explicit acknowledgment will be used. If the response indication of the response message is set to “no response” (zero (0) in some aspects, the response may indicate implicit acknowledgments will be used when relaying data. 
     The acknowledgment procedure may be indicated in some aspects by a duration field of the response message, which, in some aspects, is a null data packet acknowledgment message, and/or a NDP clear to send message. As discussed with respect to  FIG. 3H , if the first wireless device determines that explicit acknowledgments will be used when data is relayed, it may set the duration field to a value “D,” based on the equation below: 
         D =min( T   RTS   +T   PENDING   −T   PPDU   ;T   TXOP     —     REMAINING   −T   PPDU )&lt;= D&lt;=T   TXOP     —     REMAINING   −T   PPDU , 
     Where:
         T RTS  is a value of the Duration/ID field of the S1G RTS frame that elicited the response,   T PPDU  is a time, in microseconds, between the end of the PPDU carrying the RTS frame and the end of the of the NDP CTS,   T PENDING  is an estimated time for the transmission of the frame to be forwarded and its response if required plus applicable IFS durations, and   T TXOP     —     REMAINING  is equal to any T TXOP  minus T RTS , where the T TXOP  is the estimated amount of time of the current TXOP started by the TXOP initiator as known by the relay.       

     If the first wireless device determines that implicit acknowledgment will be utilized, a response indication of the response may be set to “No Response” (Zero (0) in some aspects). The duration field of the response message may also be set as described above with respect to  FIG. 3I . 
     As discussed above, a duration/ID field of a second RTS frame transmitted by the relay may be less than or equal to the TXOP for the access category minus an estimated time since the beginning of reception of the first RTS frame (which had the relayed frame field set to a first value (e.g. one) and was transmitted by the relay-shared TOP owner. The duration field of the second message may function to set a duration of a NAV used to protect the relayed transmissions during a transmission opportunity. 
     In block  1120 , the response message, is transmitted. Block  1120  may be performed in some aspects by the transmitter  210 . In some aspects, the response message is equivalent to the second message of process  600 , discussed with respect to  FIG. 6A , the second message of process  700 , discussed with respect to  FIG. 7A , and/or the second message of process  1000 , discussed with respect to  FIG. 10A . 
     When an explicit acknowledgment procedure is utilized, as described above with respect to  FIG. 3H , and frames  3020 ,  3025 , and  3030 , process  1100  may further include receiving data ( 3015 ) from the second device, acknowledging the data (via NDP acknowledgment  3020 ), and then relaying or transmitting the data ( 3025 ) to a third device. In some aspects, transmission (relaying) of the data to the third device may occur SIFS time after transmission of the acknowledgment (such as NDP acknowledgement  3020  of  FIG. 3H ) has completed. 
     When an implicit acknowledgment procedure is utilized, as described above with respect to  FIG. 3I , and frames  3115 ,  3020 ,  3125 , and  3130 , process  1100  may further include receiving data ( 3115 ), transmitting a second request-to-send message ( 3020 ), receiving a corresponding CTS message ( 3125 ), and relaying the data frame  3115  (as data frame  3130 ). Process  1100  may further include receiving an acknowledgment frame  3135  for the data frame  3130 . 
       FIG. 11B  is a functional block diagram of an exemplary device  1150  that may be employed within the wireless communication system  100 . The device  1150  includes means  1155  for receiving a first message from a second device. In an embodiment, means  1155  may be configured to perform one or more of the functions discussed above with respect to block  1105 . In an embodiment, the means for receiving 1155 may include a receiver, such as r 4 eceiver  212  of  FIG. 2 . Means  1155  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  1150  further includes means  1160  for decoding the first message to determine permission is granted to the first device to utilize at least a portion of a transmission opportunity of the second device to relay data transmitted by the second device In an embodiment, means  1160  may be configured to perform one or more of the functions discussed above with respect to block  1110 . The means for decoding  1160  may include a processor, such as processor  204  of  FIG. 2 . Means  1160  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  1150  further includes means  1165  for generating a response to the first message, the response generated to indicate an acknowledgement procedure for the relayed data. In an embodiment, means  1165  may be configured to perform one or more of the functions discussed above with respect to block  1115 . In an embodiment, the means for generating 1165 may include a processor, such as processor  204  of  FIG. 2 . Means  1165  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  1150  further includes means  1170  for transmitting the response to the second device. In an embodiment, means  1170  may be configured to perform one or more of the functions discussed above with respect to block  1120 . In an embodiment, the means for transmitting 1170 may include a transmitter, such as transmitter  210  of  FIG. 2 . Means  1170  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
       FIG. 12A  is a flowchart of a process for relaying data over a wireless communications network. In an embodiment, process  1200  may be performed by a station, such as a station  106 . In an embodiment, the first wireless device is a station and the second wireless device is an access point. In another embodiment, the first wireless device discussed below is an access point and the second wireless device is a station. In another embodiment, both the first wireless device and the second wireless device are stations. In some aspects, the first wireless device is a TXOP owner while the second wireless device is a TXOP responder and/or a relay. In some aspects, process  1200  is performed by the STA  106   a  of  FIG. 3H  or  FIG. 3I . 
     In block  1205 , a first message is generated by a first device. The first message is generated to indicate whether permission is granted to relay data transmitted by the first device during a transmission opportunity of the first device. In some aspects, the first message is generated to indicate the permission in a frame control field of the first message. Specifically, a relayed frame field and/or an order field, such as order field  387   k  of  FIG. 3E-1  or order field  388   k  of  FIG. 3E-2  may be used to indicate whether permission to relay the data during the TXOP is granted. In some aspects, the generated first message is a request-to-send message, such as the request-to-send message  3005  illustrated in  FIG. 3H  or the request-to-send message  3105  illustrated in  FIG. 3I . In some aspects, the first message of block  1205  may be the message transmitted in block  1005  of  FIG. 10A . In some aspects, the first message of block  1205  may be the first message of block  605  of  FIG. 6A . 
     In block  1210 , the first message is transmitted. 
     Some aspects of process  1200  further include receiving a second message acknowledging the first message. For example, the second message may be a null data packet acknowledgement, or a null data packet clear-to-send message, such as NDP CTS message  3010  of  FIG. 3H  and/or NDP CTS message  3110  of  FIG. 3I . Some aspects of process  1200  may decode the second message to determine an acknowledgment procedure that will be used for data relayed during the transmission opportunity. For example, whether explicit acknowledgments will be performed for relayed data, or whether an implicit acknowledgment procedure will be used may be determined by decoding the second message. In some aspects, a response indication field of a S1G PLCP preamble of the second message may be decoded to determine the acknowledgment procedure. If the response indication has a first value (for example “Long Response” or three (3) in some aspects), an explicit acknowledgment procedure may be indicated by the second message, while if the response indication has a second value (for example “No Response” or zero (0) in some aspects), an implicit acknowledgement procedure may be utilized. 
     In some aspects, the second message may be further decoded to determine a new duration of a NAV for the wireless communications network. In some aspects, if the second message indicates a different expiration time of the NAV than indicated by the first message, an explicit acknowledgment procedure will be used, while if the NAV expiration is unchanged by the second message, an implicit acknowledgment procedure will be used. In some aspects, the second message may be the second message of block  610  of  FIG. 6A , and/or the second message of block  1010  of  FIG. 10A . In these aspects, functions described with respect to methods  600  and/or  1000  may be combined with functions of method  1200 . For example, the processing of the second message of block  610  may be combined with the processing of the second message discussed here with respect to method  1200 . 
     These aspects may also include transmitting data during the transmission opportunity, and determining whether the data is acknowledged based on the indicated acknowledgment procedure. For example, when an explicit acknowledgment procedure is in use, the data may be determined to be acknowledged when an acknowledgment message is received identifying the data. When implicit acknowledgment procedures are in use, the TXOP owner may determine the data is acknowledged when the data is forwarded by a relay, and the TXOP “overhears” the relay transmission. The TXOP owner may identify the data is being relayed at least in part, on a partial AID in the PLCP header of the relayed/forwarded frame. For example, the partial AID may identify the relay/AP for the forwarded frame. 
       FIG. 12B  is a functional block diagram of an exemplary device  1250  that may be employed within the wireless communication system  100 . The device  1250  includes means  1255  for generating a first message, the first message indicating whether permission is granted to relay data transmitted by a first device during a transmission opportunity of the first device. In an embodiment, means  1255  may be configured to perform one or more of the functions discussed above with respect to block  1205 . In an embodiment, the means for generating 1255 may include a processor, such as processor  204  of  FIG. 2 . Means  1255  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     The device  1250  further includes means  1260  for transmitting the first message. In an embodiment, means  1260  may be configured to perform one or more of the functions discussed above with respect to block  1210 . The means for transmitting 1260 may include a transmitter, such as transmitter  210  of  FIG. 2 . Means  1260  may also include one or more of a processor, signal generator, transceiver, decoder, or a combination of hardware and/or software component(s), circuits, and/or module(s). 
     As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like. Further, a “channel width” as used herein may encompass or may also be referred to as a bandwidth in certain aspects. 
     As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c. 
     The various operations of methods described above may be performed by any suitable means capable of performing the operations, such as various hardware and/or software component(s), circuits, and/or module(s). Generally, any operations illustrated in the Figures may be performed by corresponding functional means capable of performing the operations. 
     The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array signal (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     In one or more aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer readable medium may comprise non-transitory computer readable medium (e.g., tangible media). In addition, in some aspects computer readable medium may comprise transitory computer readable medium (e.g., a signal). Combinations of the above should also be included within the scope of computer-readable media. 
     The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     The functions described may be implemented in hardware, software, firmware or any combination thereof. If implemented in software, the functions may be stored as one or more instructions on a computer-readable medium. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. 
     Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein. For certain aspects, the computer program product may include packaging material. 
     Software or instructions may also be transmitted over a data communications medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of data communications medium. 
     Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized. 
     It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims. 
     While the foregoing is directed to aspects of the present disclosure, other and further aspects of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.