The example embodiments relate generally to wireless networks, and specifically to delivering downlink data to stations in power save mode.
A wireless local area network (WLAN) may be formed by one or more access points (APs) that provide a shared wireless communication medium for use by a number of client devices or stations (STAs). Each AP, which may correspond to a Basic Service Set (BSS), periodically broadcasts beacon frames to enable any STAs within wireless range of the AP to establish and/or maintain a communication link with the WLAN. The beacon frames, which may include a traffic indication map (TIM) and/or a delivery traffic indication message (DTIM) indicating whether the AP has queued downlink (DL) data for one or more STAs, are typically broadcast according to a target beacon transmission time (TBTT) schedule. A TIM is typically broadcast with each beacon frame, whereas a DTIM may be broadcast at a frequency specified by a DTIM interval (e.g., once every four beacon frames).
When multiple STAs receive a TIM or a DTIM indicating that the AP has queued DL data for the STAs, each of the STAs may contend with each other for medium access to transmit a request to the AP to deliver the queued DL data. The STAs typically use an exponential backoff procedure when contending for medium access to reduce the probability of collisions on the shared wireless medium. As the number of STAs contending for medium access increases, the probability of collisions on the wireless medium also increases, which in turn may undesirably result in medium congestion, delayed delivery of queued DL data, and increased power consumption.
Accordingly, there is a need to reduce the traffic overhead and delayed service associated with delivering DL data to multiple STAs.
This Summary is provided to introduce in a simplified form a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.
Apparatuses and methods are disclosed that may facilitate the delivery of queued downlink (DL) data to a plurality of wireless devices without medium access contention operations. In one aspect, a method for a first wireless device (e.g., a STA) to receive queued DL data from a second wireless device (e.g., an AP) is disclosed. The method, which may be performed by the first wireless device, may include receiving, from the second wireless device, a beacon frame indicating a presence of a plurality of sets of queued DL data each for concurrent delivery to a corresponding one of a plurality of wireless devices, wherein the plurality of wireless devices includes the first wireless device; receiving, from the second wireless device, permission to request delivery of the queued DL data; transmitting, to the second wireless device, a request for delivery of the queued DL data based on the permission; and receiving, from the second wireless device, the set of queued DL data corresponding to the first wireless device.
In another aspect, a first wireless device is disclosed. The first wireless device may include one or more processors and a memory. The memory may store instructions that, when executed by the one or more processors, may cause the first wireless device to receive, from a second wireless device, a beacon frame indicating a presence of a plurality of sets of queued DL data each for concurrent delivery to a corresponding one of a plurality of wireless devices, wherein the plurality of wireless devices includes the first wireless device; receive, from the second wireless device, permission to request delivery of the queued DL data; transmit, to the second wireless device, a request for delivery of the queued DL data based on the permission; and receive, from the second wireless device, the set of queued DL data corresponding to the first wireless device.
In another aspect, a non-transitory computer-readable storage medium is disclosed. The non-transitory computer-readable storage medium may store one or more programs containing instructions that, when executed by one or more processors of a first wireless device, cause the first wireless device to perform a number of operations. The number of operations may include receiving, from the second wireless device, a beacon frame indicating a presence of a plurality of sets of queued DL data each for concurrent delivery to a corresponding one of a plurality of wireless devices, wherein the plurality of wireless devices includes the first wireless device; receiving, from the second wireless device, permission to request delivery of the queued DL data; transmitting, to the second wireless device, a request for delivery of the queued DL data based on the permission; and receiving, from the second wireless device, the set of queued DL data corresponding to the first wireless device.
In another aspect, a first wireless device is disclosed. The first wireless device may include means for receiving, from a second wireless device, a beacon frame indicating a presence of a plurality of sets of queued DL data each for concurrent delivery to a corresponding one of a plurality of wireless devices, wherein the plurality of wireless devices includes the first wireless device; means for receiving, from the second wireless device, permission to request delivery of the queued DL data; means for transmitting, to the second wireless device, a request for delivery of the queued DL data based on the permission; and means for receiving, from the second wireless device, the set of queued DL data corresponding to the first wireless device.
The example embodiments are illustrated by way of example and are not intended to be limited by the figures of the accompanying drawings, where:
Like reference numerals refer to corresponding parts throughout the drawing figures.
The example embodiments are described below in the context of delivering queued DL data to wireless devices in wireless local area network (WLAN) systems for simplicity only. It is to be understood that the example embodiments are equally applicable to data retrieval and delivery in other wireless networks (e.g., cellular networks, pico networks, femto networks, satellite networks), as well as for systems using signals of one or more wired standards or protocols (e.g., Ethernet and/or HomePlug/PLC standards). As used herein, the terms “WLAN” and “Wi-Fi®” may include communications governed by the IEEE 802.11 family of standards, BLUETOOTH® (Bluetooth), HiperLAN (a set of wireless standards, comparable to the IEEE 802.11 standards, used primarily in Europe), and other technologies having relatively short radio propagation range. Thus, the terms “WLAN” and “Wi-Fi” may be used interchangeably herein. In addition, although described below in terms of an infrastructure WLAN system including one or more APs and a number of STAs, the example embodiments are equally applicable to other WLAN systems including, for example, multiple WLANs, peer-to-peer (or Independent Basic Service Set) systems, Wi-Fi Direct systems, and/or Hotspots. In addition, although described herein in terms of exchanging data frames between wireless devices, the example embodiments may be applied to the exchange of any data unit, packet, and/or frame between wireless devices. Thus, the term “frame” may include any frame, packet, or data unit such as, for example, protocol data units (PDUs), MAC protocol data units (MPDUs), and physical layer convergence procedure protocol data units (PPDUs). The term “A-MPDU” may refer to aggregated MPDUs.
In the following description, numerous specific details are set forth such as examples of specific components, circuits, and processes to provide a thorough understanding of the present disclosure. The term “coupled” as used herein means connected directly to or connected through one or more intervening components or circuits. The term “associated AP” refers to an AP with which a given STA is associated (e.g., there is an established communication channel or link between the AP and the given STA). The term “non-associated AP” refers to an AP with which a given STA is not associated (e.g., there is not an established communication channel or link between the AP and the given STA, and thus the AP and the given STA may not yet exchange data frames). The term “associated STA” refers to a STA that is associated with a given AP, and the term “non-associated STA” refers to a STA that is not associated with the given AP.
Also, in the following description and for purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the example embodiments. However, it will be apparent to one skilled in the art that these specific details may not be required to practice the example embodiments. In other instances, well-known circuits and devices are shown in block diagram form to avoid obscuring the present disclosure. The example embodiments are not to be construed as limited to specific examples described herein but rather to include within their scopes all embodiments defined by the appended claims.
To conserve power, each station in a WLAN may enter a low-power state (or “power save mode”) when the station has no data to send and/or to receive from the AP. In order to maintain its connection with the AP, the station may periodically wake up from the power save mode to receive beacon frames from the AP. More specifically, the beacon frames may include a traffic indication map (TIM) and/or a delivery traffic indication message (DTIM) indicating whether the AP has queued downlink (DL) data for each of a number of stations. If the TIM or DTIM bit is asserted for a particular station, that station may remain in an awake state and contend for medium access to request delivery of the queued DL data from the AP.
As mentioned above, when an AP has queued DL data for a plurality of STAs, medium congestion, service delays, and/or increased power consumption may result from the plurality of STAs simultaneously contending for medium access to request delivery of the queued DL data. Therefore, it may be desirable to reduce the traffic overhead and delayed service associated with delivering DL data to a plurality of STAs. These are at least some of the technical problems to be solved by the example embodiments.
The IEEE 802.11ax standards may introduce multiple access mechanisms, such as an orthogonal frequency-division multiple access (OFDMA) mechanism, that allow multiple STAs to transmit and/or receive data on a shared wireless medium at the same time. The example embodiments may leverage one or more of these multiple access mechanisms to allow an AP to schedule and/or deliver queued DL data to a plurality of STAs without the plurality of STAs contending with each other for medium access to request delivery of the queued DL data. These and other details of the example embodiments, which may provide one or more solutions to the aforementioned technical problems, are described below.
Example embodiments include disclosing apparatuses and methods that allow an AP to use power save (PS) trigger frames to schedule concurrent DL data transmissions to a plurality of STAs. By using PS trigger frames to schedule delivery of queued DL data to a plurality of STAs, the plurality of STAs may not need to contend with each other for medium access to request delivery of queued DL data. Instead, a number of STAs that receive the PS trigger frame may concurrently transmit requests for delivery of the queued DL data without contending with each other for medium access, thereby reducing delays associated with medium access contention operations. Upon receiving the requests, the AP may concurrently transmit queued DL data to the requesting STAs, for example, using multiple access mechanisms. In some aspects, the AP may concurrently transmit queued DL data to multiple STAs using OFDMA communications or multi-user multiple-input multiple-output (MU-MIMO) communications. In other aspects, the AP may concurrently transmit queued DL data to multiple STAs using multiple-destination A-MPDUs (MD-AMPDUs).
Each of stations STA1-STA4 may be any suitable Wi-Fi enabled wireless device including, for example, a cell phone, personal digital assistant (PDA), tablet device, laptop computer, or the like. Each station STA may also be referred to as a user equipment (UE), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. For at least some embodiments, each STA may include one or more transceivers, one or more processing resources (e.g., processors and/or ASICs), one or more memory resources, and a power source (e.g., a battery). The memory resources may include a non-transitory computer-readable medium (e.g., one or more nonvolatile memory elements, such as EPROM, EEPROM, Flash memory, a hard drive, etc.) that stores instructions for performing operations described below with respect to
The AP 110 may be any suitable device that allows one or more wireless devices to connect to a network (e.g., a local area network (LAN), wide area network (WAN), metropolitan area network (MAN), and/or the Internet) via AP 110 using Wi-Fi, Bluetooth, or any other suitable wireless communication standards. For at least one embodiment, AP 110 may include one or more transceivers, one or more processing resources (e.g., processors and/or ASICs), one or more memory resources, and a power source. The memory resources may include a non-transitory computer-readable medium (e.g., one or more nonvolatile memory elements, such as EPROM, EEPROM, Flash memory, a hard drive, etc.) that stores instructions for performing operations described below with respect to
For the stations STA1-STA4 and/or AP 110, the one or more transceivers may include Wi-Fi transceivers, Bluetooth transceivers, cellular transceivers, and/or other suitable radio frequency (RF) transceivers (not shown for simplicity) to transmit and receive wireless communication signals. Each transceiver may communicate with other wireless devices in distinct operating frequency bands and/or using distinct communication protocols. For example, the Wi-Fi transceiver may communicate within a 900 MHz frequency band, a 2.4 GHz frequency band, a 5 GHz frequency band, and/or within a 60 MHz frequency band in accordance with the IEEE 802.11 specification. The cellular transceiver may communicate within various RF frequency bands in accordance with a 4G Long Term Evolution (LTE) protocol described by the 3rd Generation Partnership Project (3GPP) (e.g., between approximately 800 MHz and approximately 3.9 GHz) and/or in accordance with other cellular protocols (e.g., a Global System for Mobile (GSM) communications protocol). In other embodiments, the transceivers included within the STA may be any technically feasible transceiver such as a wireless personal area network (WPAN) or ZigBee transceiver described by a specification from the IEEE 802.15.4 or ZigBee specifications, a WiGig transceiver, and/or a HomePlug transceiver described a specification from the HomePlug Alliance.
The baseband processor 212 may be used to process signals received from processor 230 and/or memory 240 and to forward the processed signals to transceivers 211 for transmission via one or more of antennas 250(1)-250(n), and may be used to process signals received from one or more of antennas 250(1)-250(n) via transceivers 211 and to forward the processed signals to processor 230 and/or memory 240.
The MAC 220 may include at least a number of contention engines 221 and frame formatting circuitry 222. The contention engines 221 may contend for access to one or more shared wireless mediums, and may also store packets for transmission over the one or more shared wireless mediums. The STA 200 may include one or more contention engines 221 for each of a plurality of different access categories. For other embodiments, the contention engines 221 may be separate from MAC 220. For still other embodiments, the contention engines 221 may be implemented as one or more software modules (e.g., stored in memory 240 or stored in memory provided within MAC 220).
The frame formatting circuitry 222 may be used to create and/or format frames received from processor 230 and/or memory 240 (e.g., by adding MAC headers to PDUs provided by processor 230) and/or re-format frames received from PHY 210 (e.g., by stripping MAC headers from frames received from PHY 210).
Memory 240 may include an AP profile data store 241 that stores profile information for a number of APs. Example profile information for a particular AP may include the AP's service set identification (SSID), MAC address, channel information, received signal strength indicator (RSSI) values, goodput values, channel state information (CSI), supported data rates, supported protocols, PS-Trigger frame and other capabilities, connection history with STA 200, a trustworthiness value of the AP (e.g., indicating a level of confidence about the AP's location, etc.), and any other suitable information pertaining to or describing the operation of the AP.
Memory 240 may include a number of data queues 242. The data queues 242 may store uplink (UL) data to be transmitted from STA 200 to one or more other wireless devices. In some aspects, the memory 240 may include one or more data queues 242 for each of a plurality of destination addresses (e.g., associated with different intended recipients of the UL data). In other aspects, the memory 240 may also include one or more data queues 242 for each of a plurality of different priority levels or access categories.
Memory 240 may also include a non-transitory computer-readable medium (e.g., one or more nonvolatile memory elements, such as EPROM, EEPROM, Flash memory, a hard drive) that may store at least the following software (SW) modules:
Processor 230 may be any suitable one or more processors capable of executing scripts or instructions of one or more software programs stored in STA 200 (e.g., within memory 240). For example, processor 230 may execute the frame formation and exchange software module 243 to facilitate the creation and exchange of any suitable frames (e.g., data frames, action frames, control frames, and management frames) between STA 200 and other wireless devices. Processor 230 may also execute the power save management software module 244 to facilitate STA 200's entry into a power save mode (e.g., upon determining that an AP has no queued DL data for STA 200) and/or to facilitate STA 200's exit from the power save mode (e.g., to enter an awake state and receive a beacon frame, a trigger frame, and/or DL data from the AP). Processor 230 may also execute the queued data retrieval software module 245 to determine whether an AP has queued DL data for STA 200, to generate responses to PS-Trigger frames received from the AP, and/or to retrieve queued DL data from the AP.
The baseband processor 312 may be used to process signals received from processor 330 and/or memory 340 and to forward the processed signals to transceivers 311 for transmission via one or more of antennas 360(1)-360(n), and may be used to process signals received from one or more of antennas 360(1)-360(n) via transceivers 311 and to forward the processed signals to processor 330 and/or memory 340.
The network interface 350 may be used to communicate with a WLAN server (not shown for simplicity) either directly or via one or more intervening networks. Processor 330 may be any suitable one or more processors capable of executing scripts or instructions of one or more software programs stored in AP 300 (e.g., within memory 340).
The MAC 320 may include at least a number of contention engines 321 and frame formatting circuitry 322. The contention engines 321 may contend for access to the shared wireless medium and may also store packets for transmission over the shared wireless medium. For some embodiments, AP 300 may include one or more contention engines 321 for each of a plurality of different access categories. For other embodiments, the contention engines 321 may be separate from MAC 320. For still other embodiments, the contention engines 321 may be implemented as one or more software modules (e.g., stored in memory 340 or within memory provided within MAC 320).
The frame formatting circuitry 322 may be used to create and/or format frames received from processor 330 and/or memory 340 (e.g., by adding MAC headers to PDUs provided by processor 330) and re-format frames received from PHY 310 (e.g., by stripping MAC headers from frames received from PHY 310).
Memory 340 may include a STA profile data store 341 that stores profile information for a number of STAs. The profile information for a particular STA may include information including, for example, its MAC address, supported data rates, supported protocols, PS-Trigger frame and other capabilities, connection history with AP 300, and any other suitable information pertaining to or describing the operation of the STA.
Memory 340 may also include a number of data queues 342. The data queues 342 may store downlink (DL) data to be transmitted from AP 300 to one or more other wireless devices. In some aspects, the memory 340 may include one or more data queues 342 for each of a plurality of destination addresses (e.g., corresponding to a plurality of different STAs that are to receive DL data from AP 300). More specifically, as described in more detail below with respect to
Memory 340 may also include a non-transitory computer-readable medium (e.g., one or more nonvolatile memory elements, such as EPROM, EEPROM, Flash memory, a hard drive, and so on) that may store at least the following software (SW) modules:
For example, processor 330 may execute the frame formation and exchange software module 343 to facilitate the creation and exchange of any suitable frames (e.g., data frames, action frames, control frames, and management frames) between AP 300 and other wireless devices. Processor 330 may also execute the downlink data management software module 344 to facilitate the queuing of DL data for STAs, to notify STAs of the presence of queued DL data, to trigger STAs to request delivery of queued DL data, and/or to transmit DL data to requesting STAs. Processor 330 may also execute the medium congestion determination software module 345 to facilitate the determination of a level of congestion on a shared wireless medium, to compare the determined level of congestion with a threshold value, and/or to selectively enable the use of PS-Trigger frames (e.g., to schedule the delivery of queued DL data to a number of STAs) based on the comparison.
The data queues 410(1)-410(4), which may be one embodiment of the data queues 342 of
More specifically, for the example of
The contention engines 420, which may be one embodiment of contention engines 321 of
It is noted that the STA 200 of
As mentioned above, the example embodiments may allow an AP to use PS-Trigger frames to schedule concurrent DL data transmissions to a plurality of STAs without the STAs contending for medium access to request delivery of the queued DL data. In some aspects, a STA may indicate its capabilities to decode PS-Trigger frames and/or to request delivery of queued DL data based on decoded PS-Trigger frames during association with an AP. The STA may indicate its PS-Trigger frame capabilities in any suitable manner including, for example, asserting a PS-Trigger frame capabilities bit in an association request, a probe request, or other suitable control and/or management frame transmitted to the AP.
For some implementations, an AP may use an enhanced TIM element in a beacon frame to indicate that the receiving STAs are not to contend for medium access to request delivery of queued DL data, but rather are to wait for permission (granted by the AP) to transmit a request for delivery of the queued DL data. In this manner, medium access contention operations associated with requesting delivery of queued DL data from the AP may be avoided.
Because not all STAs may indicate support for PS-Trigger frames, the AP may allow some STAs (e.g., that do not support PS-Trigger frame capabilities) to contend for medium access to request delivery of queued DL data. For example, if a first group of STAs has not indicated support for PS-Trigger frame capabilities, then the AP may allow the first group of STAs to contend for medium access to request delivery of queued DL data. Further, if a second group of STAs has indicated support for PS-Trigger frame capabilities, then the AP may use PS-Trigger frames to schedule delivery of queued DL data to the second group of STAs, for example, while allowing the first group of STAs to contend for medium access to request delivery of queued DL data.
For at least some implementations, the AP may selectively use PS-Trigger frames to schedule delivery of queued DL data based on a level of congestion on the shared wireless medium. For example, if there is relatively little traffic or congestion on the wireless medium, then the time associated with transmission of PS-Trigger frames may be greater than the time associated with medium access contention operations to request delivery of queued DL data. Conversely, if there is relatively heavy traffic or congestion on the wireless medium, then the time associated with transmission of PS-Trigger frames may be less than the time associated with medium access contention operations to request delivery of queued DL data.
More specifically, in accordance with example embodiments, the AP may determine a level of congestion on the wireless medium, compare the level of congestion with a threshold value, and then selectively use PS-Trigger frames to schedule delivery of queued DL data based on the comparison. For example, if the level of congestion on the wireless medium exceeds the threshold value, then the AP may use PS-Trigger frames to schedule delivery of queued DL data. Conversely, if the level of congestion on the wireless medium does not exceed the threshold value, then the AP may not use PS-Trigger frames to schedule delivery of queued DL data, but rather allow the STAs to contend for medium access to request delivery of queued DL data.
As depicted in
Each of the stations STA1-STA4 that is in power save mode may exit power save mode to receive the beacon frame 510 (e.g., by waking up in accordance with the TBTT schedule). Upon receiving the beacon frame 510 between times t0 and t1, each of the stations STA1-STA4 may decode the TIM or DTIM element provided therein to determine whether AP 110 has queued DL data for the STA. In some aspects, the beacon frame 510 may include an enhanced TIM element indicating that the receiving STAs are not to contend for medium access to request delivery of queued DL data. Instead, receiving STAs are to wait for permission (granted by the AP) to transmit a request for delivery of the queued DL data. If the AP 110 does not have queued DL data for a STA, then the STA may re-enter power save mode (e.g., and thus not be awake to receive a PS-Trigger frame). Conversely, if the AP 110 has queued DL data for a STA, then the STA may remain awake to receive a PS-Trigger frame. For the example of
Between times t2 and t3, the AP 110 may transmit a PS-Trigger frame 520. The PS-Trigger frame 520 may indicate or identify which of the receiving stations STA1-STA4 are to request queued DL data from AP 110. In some implementations, if the PS-Trigger frame 520 instructs a STA to request queued DL data from AP 110, then the STA may either transmit a PS-Poll frame to the AP 110 or transmit a Null Data frame having a de-asserted power management bit (e.g., PM=0) to the AP 110. As discussed above, a de-asserted power management bit may indicate that the corresponding STA is to remain in the awake state, and may therefore receive queued DL data from AP 110.
Conversely, if the PS-Trigger frame 520 does not instruct a STA to request queued DL data from AP 110, then the STA may defer from contending for medium access for a wait period (e.g., by setting a duration of its network allocation vector (NAV) to the wait period). In some aspects, the wait period may be predetermined (e.g., agreed upon during association). In other aspects, the wait period may be dynamically adjusted.
Between times t4 and t5, each STA that was instructed (e.g., by the PS-Trigger frame 520) to request delivery of queued DL data may transmit a request, to the AP 110, to deliver the queued DL data. The request may be a PS-Poll frame or a Null Data frame having its PM bit set to 0 (e.g., to indicate that the STA will remain awake). For the example of
Between times t6 and t7, the AP 110 may transmit queued DL data to stations STA1-STA3. In some aspects, the AP 110 may concurrently transmit the queued DL data to stations STA1-STA3 using either OFDMA communications or MU-MIMO communications. In other aspects, the AP 110 may concurrently transmit the queued DL data to stations STA1-STA3 as MD-AMPDUs. For the example depicted in
After receiving the DL data from the AP 110, each of the stations STA1-STA3 may transmit an acknowledgement between times t8 and t9 to confirm reception of the DL data. In some aspects, a STA may send an acknowledgement (ACK) frame to AP 110 to confirm reception of a single data packet (e.g., an MPDU), and may send a block acknowledgement (BA) frame to AP 110 to confirm reception of a number of aggregated data packets (e.g., an A-MPDU). Thus, for the example depicted in
As depicted in
The time period 511 between times t1 and t2 may allow STAs in power save mode sufficient time to wake up and receive the PS-Trigger frame 520. In some implementations, a duration of the time period 511 may be negotiated during association procedures between the AP 110 and stations STA1-STA4. As an addition or as an alternative, the duration of the time period 511 may be indicated in one or more beacon frames (e.g., beacon frame 510) transmitted from the AP 110. In some aspects, the duration of the time period 511 may be provided within an information element (IE) or a vendor-specific information element (VSIE) included within or appended to the beacon frames. In other aspects, the duration of the time period 511 may be indicated using a number of reserved bits in the beacon frames.
As described above with respect to
For some implementations, when the AP 110 has queued DL data for a plurality of STAs, the AP 110 may divide the plurality of STAs into a number of groups and then transmit queued DL data to the STAs in the same group at the same time. The AP 110 may assign each associated STA to a corresponding group of STAs and then transmit a separate PS-Trigger frame to each group of STAs at a different time. In response thereto, the STAs within each group may request delivery of queued DL data from the AP 110 at the same time. The AP 110 may schedule delivery of queued DL data to different groups of STAs at different (e.g., staggered) times. In some aspects, the AP 110 may assign each STA to a particular group of STAs during an association procedure between the AP 110 and the STA. For example, the AP 110 may assign a STA to a particular group based on the STA's device type (e.g., smartphone, laptop, tablet, etc.). In other aspects, a wireless standard by which the AP 110 and a STA operate may specify to which group the STA is to be assigned by the AP 110.
The AP 110 may assign a unique offset time to each group of STAs, and then schedule transmission of the PS-Trigger frames to the respective groups of STAs based on their corresponding unique offset times. In some aspects, the offset time may indicate a specific time, relative to the beacon frame transmission (e.g., the TBTTs), at which the STAs assigned to the corresponding group of STAs may expect to receive a PS-Trigger frame.
For other embodiments, the PS-Trigger frame 520 may not identify all associated STAs that are to request queued DL data from the AP 110. For one example, the PS-Trigger frame 520 may identify one or more selected groups of STAs that are to request delivery of queued DL data using PS-Poll frames or Null Data frames (e.g., in the manner described above with respect to
For other embodiments, the AP 110 may not transmit the PS-Trigger frame to the receiving STAs, and the receiving STAs may not transmit PS-Poll frames or Null Data frames to the AP 110 (e.g., in contrast to the example depicted in
As depicted in
Each of the stations STA1-STA4 that is in power save mode may exit power save mode to receive the beacon frame 610 (e.g., by waking up in accordance with the TBTT schedule). Upon receiving the beacon frame 610, each of the stations STA1-STA4 may decode the beacon frame 610 to determine whether the AP 110 has queued DL data for the STA. If the AP 110 does not have queued DL data for a STA, then the STA may re-enter power save mode. Conversely, if the AP 110 has queued DL data for a STA, then the STA may remain awake to receive the queued DL data from the AP 110. For the example of
In contrast to the example operation of
Between times t2 and t3, the AP 110 may concurrently transmit queued DL data to each of the receiving stations STA1-STA3. In some aspects, the AP 110 may concurrently transmit the queued DL data to stations STA1-STA3 using either OFDMA communications or MU-MIMO communications. In other aspects, the AP 110 may concurrently transmit the queued DL data to stations STA1-STA3 as MD-AMPDUs. For the example of
After receiving the DL data from the AP 110, each of the stations STA1-STA3 may transmit an acknowledgement between times t4 and t5 to confirm reception of the DL data. In some aspects, a STA may send an ACK frame to the AP 110 to confirm reception of a single data packet (e.g., an MPDU), and may send a BA frame to the AP 110 to confirm reception of a number of aggregated data packets (e.g., an A-MPDU). Thus, for the example depicted in
In some aspects, each of the stations STA1-STA3 may indicate its power management state in ACK frames and/or BA frames transmitted to the AP 110. For the example of
In accordance with example embodiments, by informing the AP 110 that they will remain in the awake state after time t5, STA2 and STA3 may each expect to receive additional queued DL data from the AP 110 at or around time t6. The time period 631 between times t5 and t6, which may indicate how long after completion of the acknowledgement transmissions (e.g., BA frame 635 and ACK frame 630(3)) respective stations STA2 and STA3 may expect to receive the additional queued DL data from the AP 110, may be any suitable time period. In some aspects, the time period 631 may be negotiated between the AP 110 and stations STA1-STA4, for example, during association procedures or during an exchange of Implicit PS-Trigger capabilities. In other aspects, the time period 631 may be indicated to stations STA1-STA4 in beacon frames (e.g., beacon frame 610) and/or any other suitable management frame or control frame.
Between times t6 and t7, the AP 110 may transmit the additional queued DL data to stations STA2 and STA3. For the example of
At time t8, each of stations STA2-STA3 may transmit an acknowledgement to confirm reception of the additional queued DL data. More specifically, for the example of
As depicted in
The second wireless device may determine, for each of a plurality of first wireless devices, a presence of a corresponding set of queued DL data (701). In some aspects, the second wireless device may determine the presence of queued DL data by executing downlink data management SW module 344 of
As described above, each of the first wireless devices may decode the TIM or DTIM and determine whether there is any DL data for the first wireless device queued in the second wireless device. For example, referring also to
Then, the second wireless device may transmit, to each of the identified first wireless devices, permission to request delivery of queued DL data (703). For some implementations, the permission may be a PS-Trigger frame, for example, as described above with respect to
Next, the second wireless device receive, from each of the identified first wireless devices, a request for delivery of the queued DL data (704). The request for delivery of the queued DL data may be a PS-Poll frame or a Null Data frame having a PM bit set to 0 (e.g., to indicate that a corresponding one of the first wireless devices will remain in the awake state). For some implementations, the requests for delivery of the queued DL data may be received concurrently using UL OFDMA communications or UL MU-MIMO communications. In some aspects, the requests for queued DL data may be received by executing one or more of frame formation and exchange SW module 343 and downlink data management SW module 344.
After receiving the requests, the second wireless device may concurrently transmit, to each of the identified first wireless devices, the corresponding set of queued DL data (705). For some implementations, the queued DL data may be transmitted using OFDMA communications or MU-MIMO communications. For other implementations, the queued DL data may be transmitted as one or more MD-AMPDUs. In some aspects, the requested queued DL data may be transmitted by executing one or more of frame formation and exchange SW module 343 and downlink data management SW module 344.
The second wireless device may receive an acknowledgment from each of the identified first wireless devices (706). Each of the acknowledgments may be an ACK frame or a BA frame, and may indicate a power save mode status for a corresponding one of the first wireless devices. For some implementations, the acknowledgments may be received concurrently using UL OFDMA communications or UL MU-MIMO communications. In some aspects, the acknowledgments may be received by executing one or more of frame formation and exchange SW module 343 and downlink data management SW module 344.
The first wireless device may receive, from the second wireless device, a beacon frame indicating a presence (or not) of a plurality of sets of queued DL data each for concurrent delivery to a corresponding one of a plurality of wireless devices, the plurality of wireless devices including the first wireless device (801). The first wireless device may have exited a power save mode and entered an awake state, for example, according to a TBTT schedule to receive the beacon frame. The presence of queued DL data may be indicated by a TIM or a DTIM included in the beacon frame. In some aspects, the beacon frame may include an enhanced TIM element indicating that the first wireless device is not to contend for medium access to request delivery of queued DL data, but rather is to wait for permission (granted by the AP) to transmit a request for delivery of the queued DL data. The first wireless device may receive the beacon frame by executing one or more of frame formation and exchange SW module 243, power save management SW module 244, and queued data retrieval SW module 245.
Next, the first wireless device may receive, from the second wireless device, permission to request delivery of the queued DL data (802). The permission may be a PS-Trigger frame, for example, as described above with respect to
The first wireless device may transmit, to the second wireless device, a request for delivery of the queued DL data based on the permission (803). The request for delivery of the queued DL data may be a PS-Poll frame or a Null Data frame having a PM bit set to 0 (e.g., to indicate that the first wireless device will remain in the awake state). In some aspects, the first wireless device may generate and transmit the request for delivery of the queued DL data by executing one or more of frame formation and exchange SW module 243, power save management SW module 244, and queued data retrieval SW module 245.
Then, the first wireless device may receive, from the second wireless device, the corresponding set of queued DL data (804). For some implementations, the queued DL data may be received as OFDMA communications or as MU-MIMO communications. For other implementations, the queued DL data may be received as one or more MD-AMPDUs. In some aspects, the first wireless device may receive the queued DL data by executing one or more of frame formation and exchange SW module 243, power save management SW module 244, and queued data retrieval SW module 245.
The first wireless device may transmit an acknowledgment to acknowledge reception of the queued DL data (805). The acknowledgment may be an ACK frame or a BA frame. For some implementations, the acknowledgment may indicate a power save mode status of the first wireless device. In some aspects, the first wireless device may generate and transmit the acknowledgment by executing one or more of frame formation and exchange SW module 243, power save management SW module 244, and queued data retrieval SW module 245.
Those of skill in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.
Further, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosure.
The methods, sequences or algorithms described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.
In the foregoing specification, the example embodiments have been described with reference to specific example embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader scope of the disclosure. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.
This application claims priority to co-pending and commonly owned U.S. Provisional Patent Application No. 62/161,019 entitled “POWER SAVE TRIGGER” filed on May 13, 2015 and to co-pending and commonly owned U.S. Provisional Patent Application No. 62/162,061 entitled “POWER SAVE TRIGGER” filed on May 15, 2015, the entireties of both are incorporated by reference herein.
Number | Date | Country | |
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62161019 | May 2015 | US | |
62162061 | May 2015 | US |