Enhanced fine timing measurement protocol negotiation

This disclosure describes systems, methods, and devices related to enhanced fine timing measurement protocol negotiation. A device may identify an enhanced fine timing measurement request received from a first device, the enhanced fine timing measurement request comprising one or more information elements associated with one or more multiple-input multiple-output (MIMO) parameters. The device may cause to send an enhanced fine timing measurement response to the first device. The device may identify a null data packet announcement associated with a location determination of the first device. The device may identify a null data packet received from the first device. The device may cause to send a null data packet feedback to the first device.

TECHNICAL FIELD

This disclosure generally relates to systems and methods for wireless communications and, more particularly, to protocol negotiation.

BACKGROUND

Communication devices in wireless systems are becoming widely prevalent and are increasingly requesting services from other communication devices. One of these services is the ability to determine a range or a distance between two communication devices by measuring the time that it takes for the wireless signal to travel from one device to the other.

DETAILED DESCRIPTION

Example embodiments described herein provide certain systems, methods, and devices for enhanced fine timing measurement (EFTM) protocol negotiation, including, but not limited to, the IEEE 802.11 family of standards.

A Wi-Fi device may perform a timing measurement procedure, known as fine timing measurement (FTM), in order to allow the Wi-Fi device to determine its range to another device, such as an access point or an FTM responder. The FTM procedure is an IEEE 802.11 protocol introduced to support location determination based on the range measurement to multiple known responding devices and the execution of location determination techniques, for example, triangulation, trilateration, etc.

An FTM procedure may have three phases: a capabilities exchange phase, a measurements phase, and a termination phase. The FTM procedure utilizes management frames as opposed to control frames and Null Data Packet (NDP) frames in order to perform the measurements between an initiator device and a responder device. The FTM operates in both the associated and unassociated modes. REVmc protocol is defined for both very high throughput (VHT) (e.g., IEEE 802.11ac) and high throughput (HT) (e.g., IEEE 802.11n) station devices (STAs) but is essentially a single-input single-output (SISO) protocol using pre-VHT compatible format acknowledgment (ACK) (e.g., Non-HT duplicate ACK) and one transmit chain for each measurement.

A variant of the VHT sounding protocol may be modified in order to include an enhanced FTM request. However, with the introduction of high efficiency multi-user (HE-MU) as one of the predominant modes, the resulting scheduling mechanism in which free access to the channel gets lower probability, gets even lower the more the medium becomes congested.

Example embodiments of the present disclosure relate to systems, methods, and devices for FTM trigger frame signaling.

In one embodiment, an enhanced FTM (EFTM) protocol may include a capabilities exchange phase, a measurements phase, and a termination phase.

In one embodiment, an EFTM protocol negotiation system may be utilized to perform timing measurements between the initiating device and the responder device using control frames as opposed to management frames. Management frames have advantages in terms of negotiation because management frames do not require an immediate response in SIFS (Short Inter-frame Space) time (normally 16 usec) when received. However, management frames require additional processing time. Typically, FTM requires a downlink and uplink paths between the initiator device and the responder device, since the Initiating device in many cases is a client and may not be available “on channel” continuously due to power considerations and other radio activities (e.g., association to an AP on another channel), the FTM protocol provides a means to indicate “on channel availability” at the beginning of the measurement phase, in the REVmc protocol this is done using management frames and followed by management (FTM measurement) and control frame (ACK) for measurement execution. The downside this scheme is that using management frames for “on channel availability” indication is that the processing time of that, is quite long, normally in the 5-10 msec long, and management and control frames provide poor framework for high accuracy medium measurement (AKA channel sounding) to not make use of MIMO as well as other frame formats (ACK frames mandated to use Non-HT Duplicate format which does not contain the VHT-LTF fields at the PPDU level).

Typically, control frames have limited and simpler structures than management frames. Meaning that baseband processing may process control frames using a simpler procedure, resulting in faster processing (e.g., in microseconds). However, control frames are less flexible than management frames and are poor framework for complex signaling such as one used for negotiation and capability exchange phase. Control frames are fixed in size while management frames are capable being extended to add new capabilities. Management frames are not limited or fixed in size. Further, control frames may not include information elements, which may be used to extend the management frames.

In one embodiment, the EFTM protocol negotiation system may include a backward-compatible negotiation that may enable the measurement protocol to operate in both the associated and the unassociated modes, and may provide a single capability exchange and resource allocation negotiation used for multiple measurement exchanges, which minimizes the medium overhead caused by the negotiation.

In one embodiment, an EFTM protocol negotiation system may introduce a capabilities exchange phase that includes the functionality of the negotiation phase of the FTM procedure. The capabilities exchange phase may utilize one or more management frames that may be enhanced to include additional information. The capabilities exchange phase may include one or more information elements (IEs) that may be added to an FTM request frame. A benefit of the management frames as opposed to the control frames is that management frames may be modified to include additional IEs. Additionally, a legacy device that receives the FTM request that includes unrecognized additional IEs may ignore those IEs, which in turn makes the EFTM protocol negotiation system to be backward-compatible with legacy devices. For example, the EFTM protocol negotiation system may be backward-compatible with the existing legacy REVmc protocol, such that an IEEE 802.11az device may be able to communicate with a VHT access point (AP) or legacy device supporting legacy FTM (i.e. STDS IEEE 802.11-2016 FTM) in a legacy compatible way, while using the new operational mode when both AP and device are IEEE 802.11az capable. One of the advantages is that the negotiation with legacy STA is not necessarily needed in the legacy mode. Legacy STAs are mandated to ignore unrecognized (new) IEs so the new STA includes both the legacy and new IEs and legacy STAs process only the legacy IEs while new STAs supporting the new mode process both legacy and new IEs.

In one embodiment, an EFTM protocol negotiation system may utilize one or more control frames and physical layer (PHY) convergence protocol data unit (PPDU) (e.g., NDP) during the measurements phase of the FTM procedure. The EFTM protocol negotiation system may keep the flexibility of the management frames during the capabilities exchange phase while enhancing the entire FTM procedure by decreasing the time it takes to perform the measurements by using control frames, which do not require as much waiting time between frames as management frames. The measurements phase may include an exchange of null data packets (NDPs) between the AP and an STA. An NDP is a physical layer (PHY) protocol data unit (PPDU) that carries no data field.

In one embodiment, the EFTM protocol negotiation system may facilitate an IEEE 802.11az STA to transmit an enhanced FTM request, in post discovery (e.g., using active or a passive scan beacon), that may include a new IE for supporting the enhanced VHT and HE (High Efficiency IEEE 802.11ax) multiple-input multiple-output (MIMO) parameters indicating the capabilities of the STA (e.g., number of supported transmit (TX) chains, number of supported receive (RX) chains, supported bandwidths, etc.) together with its legacy capabilities (e.g., existing REVmc FTM parameters, location configuration information (LCI) request indication, etc.).

The 802.11ac protocol uses a referencing mechanism for the media access control (MAC) address that uses what is known as an associated ID (AID) instead of the MAC address. The MAC addresses are typically hardcoded in the devices during manufacturing. However, the AID or Pre-AID (Pre-association ID) assigned to the device during association. Therefore, one additional consideration for the EFTM protocol negotiation system is to introduce a new addressing mechanism during the pre-association phase because the MAC addressing is not compatible with it and because the FTM procedure has to operate in the associated and the unassociated modes. In the unassociated cases, addressing is not yet established since the AID would not have been assigned yet. Therefore, the EFTM protocol negotiation system may facilitate a new addressing mechanism in order to account for the unassociated cases; however, this new addressing mechanism may also apply to the associated mechanism. The new addressing mechanism is referred to hereinafter as a pre-association ID (pre-AID) or an unassociated ID (UID). The terms pre-AID and UID maybe interchangeable within this disclosure. In the associated mode, a device may use an AID or a UID.

During the capabilities exchange phase, if the device is already associated with the AP, then both the device and the AP know each other's capabilities. During association, the security context is established. In the case of the EFTM procedure, the security context may be desirable. Consequently, the one or more additional IEs may include an IE associated with the security context that may be exchanged between the AP and the STA.

In one embodiment, the EFTM protocol negotiation system may be configured to allow a legacy AP to ignore the newly defined IE and may respond with a legacy FTM response frame, while an IEEE 802.11az capable AP may respond with an FTM response frame including a new IEEE 802.11az IE providing its capabilities (e.g., supported bandwidth, number of supported TX chains, number of supported Rx chains, LCI for all antennas) and may assign a unique identifier for the unassociated operation unique identifier (UID). The UID may be maintained using a keep alive process of transmitting a null data packet announcement (NDPA) for location, and resetting the timer. If no NDPA is received within a certain defined period of time, the UID may expire and the AP may assign the UID to another STA.

FIG.1depicts a network diagram illustrating an example network environment for an EFTM protocol negotiation, according to some example embodiments of the present disclosure. Wireless network100may include one or more user devices120and one or more responding device(s) (e.g., AP102), which may communicate in accordance with IEEE 802.11 communication standards. The user device(s)120may be mobile devices that are non-stationary (e.g., not having fixed locations) or may be stationary devices.

In some embodiments, the user devices120and the AP102may include one or more computer systems similar to that of the functional diagram ofFIG.6and/or the example machine/system ofFIG.7.

The user device(s)120and/or AP(s)102may also include mesh stations in, for example, a mesh network, in accordance with one or more IEEE 802.11 standards and/or 3GPP standards.

Any of the user device(s)120(e.g., user devices124,126,128) and AP(s)102may include one or more communications antennas. The one or more communications antennas may be any suitable type of antennas corresponding to the communications protocols used by the user device(s)120(e.g., user devices124,126and128), and AP(s)102. Some non-limiting examples of suitable communications antennas include Wi-Fi antennas, Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards compatible antennas, directional antennas, non-directional antennas, dipole antennas, folded dipole antennas, patch antennas, multiple-input multiple-output (MIMO) antennas, omnidirectional antennas, quasi-omnidirectional antennas, or the like. The one or more communications antennas may be communicatively coupled to a radio component to transmit and/or receive signals, such as communications signals to and/or from the user devices120and/or AP(s)102.

Any of the user device(s)120(e.g., user devices124,126,128), and AP(s)102may be configured to perform directional transmission and/or directional reception in conjunction with wirelessly communicating in a wireless network. Any of the user device(s)120(e.g., user devices124,126,128), and AP(s)102may be configured to perform such directional transmission and/or reception using a set of multiple antenna arrays (e.g., directional multi-gigabit (DMG) antenna arrays or the like). Each of the multiple antenna arrays may be used for transmission and/or reception in a particular respective direction or range of directions. Any of the user device(s)120(e.g., user devices124,126,128), and AP(s)102may be configured to perform any given directional transmission towards one or more defined transmit sectors. Any of the user device(s)120(e.g., user devices124,126,128), and AP(s)102may be configured to perform any given directional reception from one or more defined receive sectors.

MIMO beamforming in a wireless network may be accomplished using RF beamforming and/or digital beamforming. In some embodiments, in performing a given MIMO transmission, user devices120and/or AP(s)102may be configured to use all or a subset of its one or more communications antennas to perform MIMO beamforming.

When an AP (e.g., AP102) establishes communication with one or more user devices120(e.g., user devices124,126, and/or128), the AP102may communicate in a downlink direction and the user devices120may communicate with the AP102in an uplink direction by sending frames in either direction. The user devices120may also communicate peer-to-peer or directly with each other with or without the AP102. The frames may be preceded by one or more preambles that may be part of one or more headers. These preambles may be used to allow a device (e.g., AP102and/or user devices120) to detect a new incoming data frame from another device. A preamble may be a signal used in network communications to synchronize transmission timing between two or more devices (e.g., between the APs and user devices).

The IEEE 802.11 standard defines various frame types that devices may use for communications as well as managing and controlling the wireless link. These frame types may include data frames or signaling frames. The signaling frames may be divided into control frames and management frames. Management frames enable devices to establish and maintain communications. Some examples of management frames may include, but are not limited to, fine timing measurement frame, authentication frames, association request frame, association response frame, beacon frame, etc. control frames may assist in the delivery of data frames between devices. Some examples of control frames may include, but our not limited to, request to send frame, clear to send frame, acknowledgment frame, null data packet frame (NDP), etc.

Typically, control frames have limited and simpler structures than management frames. Meaning that baseband processing may process control frames using a simpler procedure, resulting in faster processing. However, control frames are less flexible than management frames.

With reference toFIG.1, the one or more user devices120and/or the AP102may perform an EFTM procedure. The EFTM procedure may, for example, determine the location of an initiating device (e.g., the user devices120) based on time differences between various frames sent and received between the initiating device and a responding device (e.g., the AP102). An EFTM procedure may start with the initiating device (e.g., user device124) sending a request to establish the EFTM service (e.g., request to establish EFTM service140) to a responding device (e.g., the AP102). The responding device may respond by sending an EFTM response142). It is understood that the above descriptions are for purposes of illustration and are not meant to be limiting.

FIG.2Adepicts an illustrative schematic diagram of an FTM procedure between an initiating device and a responding device.

With reference toFIG.2A, there is shown an initiating device222and a responding device202. The initiating device222and the responding device202may be involved in an FTM procedure in order for the initiating device222to determine, at least in part, its range to the responding device202. When performing the FTM procedure, the initiating device222may start the FTM procedure by sending an initial FTM request232to the responding device202. The responding device202may send an acknowledgment (e.g., Ack234) to the initiating device222. The responding device202may determine a delay236before sending a first FTM frame238to the initiating device222. The first FTM frame238may include information to inform the initiating device222of the burst duration and the burst period that the FTM procedure will be carried out for measuring delays in order to determine the location of the initiating device222. When the initiating device222receives the first FTM frame238, the initiating device222may process the first FTM frame238. Each time the initiating device222receives a frame from the responding device202and vice versa, a certain delay may increase the overall duration of the FTM measurements due to processing time for the received frames. The initiating device222may send an acknowledgment (e.g., Ack242) in response to the received first FTM frame238. The initiating device222and the responding device202may perform the FTM messaging in order to take time measurements within a burst duration244. The responding device202, at time t1_2may send the second FTM frame250and start the time measurement. At time t2_2, the initiating device222may receive the second FTM frame250. After a processing delay, at time t3_2, the initiating device222may send an Ack252to the responding device202. The Ack252may be received by the responding device202at time t4_2. The responding device202may send a third FTM frame254at time t1_3to the initiating device222. The third FTM frame254may be received by the initiating device222at time t2_3, and the initiating device222may respond by sending Ack258at time t3_3. The Ack258may be received by the responding device202at time t4_3.

FIG.2Bdepicts an illustrative flow diagram of a variant of the VHT sounding protocol, in accordance with one or more example embodiments of the present disclosure.

In one embodiment, an EFTM protocol negotiation system may facilitate the use of a variant of a VHT sounding protocol that uses one or more null data packets (NDPs) in order to perform a VHT sounding procedure. A VHT sounding protocol is an explicit beamforming mechanism where a beamformer sends an NDP to the beamformee and the beamformee receives the NDP and creates a steering feedback that is sent to the beamformer.

A VHT sounding protocol uses control frames instead of management frames in order to achieve the sounding measurements. However, the VHT sounding mechanism may include one or more shortcomings that may need to be addressed. For example, with the introduction of high efficiency multi-user (HE-MU) as one of the predominant modes, the resulting scheduling mechanism in which free access to the channel gets lower probability, gets even lower the more the medium becomes congested.

Further, the VHT protocol operates in the associated mode, meaning that a device is already associated with an AP, while the EFTM protocol is required to operate in the unassociated mode as well as the associated mode. This may mean that no AID (Association ID) has been assigned to the STA yet (e.g., initiator262), and no AP (e.g., responder252) or STA capability exchange (e.g., bandwidth, modulation, number of transmit (TX) and receive (RX) chains, etc.) has been negotiated between the initiator262and the responder252.

In one embodiment, an EFTM protocol negotiation system may enhance the VHT sounding protocol by using an EFTM request254followed by NDP frame256from the initiator262to the responder252. The responder252may respond with NDP frame258followed by an EFTM response260. However, an EFTM protocol negotiation system may take into account other considerations for an FTM procedure to be used to determine the range of the initiator262to the responder252.

In one embodiment, an EFTM protocol negotiation system may enhance the VHT sounding protocol by introducing a new addressing mechanism in order to overcome the problems with the VHT sounding protocol. For example, one additional consideration for the EFTM protocol negotiation system is to introduce a new addressing mechanism because the MAC addressing is not compatible with it and because the FTM procedure has to operate in the associated and the unassociated modes. In the unassociated cases, addressing is not yet established since the AID would not have been assigned yet. Therefore, the EFTM protocol negotiation system may facilitate a new addressing mechanism in order to account for the unassociated cases; however, this new addressing mechanism may also apply to the associated mechanism. The new addressing mechanism is referred to hereinafter as an unassociated ID (UID). In the associated mode, a device may use an AID or a UID.

In one embodiment, the EFTM protocol negotiation system may be configured to be backward-compatible with legacy devices. The EFTM protocol negotiation system may allow a legacy AP to ignore the newly defined IE and may respond with a legacy FTM response frame, while an IEEE 802.11az capable AP may respond with an FTM response frame including a new IEEE 802.11az IE providing its capabilities (e.g., bandwidth, number of supported TX chains, number of supported RX chains, LCI for all antennas) and may assign a unique identifier for the unassociated operation unique identifier (UID).

In one embodiment, an EFTM protocol negotiation system may facilitate the use of a variant of the VHT sounding protocol to perform one or more repeated measurements to perform an FTM procedure to determine the range of the initiator262to the responder252. In one example, an EFTM protocol negotiation system may employ the use of control frames, such as NDP frames, for the repeated measurements to perform an FTM procedure. It is understood that the above descriptions are for purposes of illustration and are not meant to be limiting.

FIG.3depicts an illustrative flow diagram for EFTM protocol negotiation, in accordance with one or more example embodiments of the present disclosure.

With reference toFIG.3, there is shown an EFTM message flow between a responding device (e.g., AP302) and an initiating device (e.g., STA322). The EFTM protocol negotiation system may include a capabilities exchange phase330, a repeated measurements phase332, and a termination phase334. An EFTM message flow may include a combination of REVmc FTM flow and a modified version of sounding VHT measurement used for location determination. In one example, the EFTM message flow may be performed with an STA (e.g., STA322) that may be either associated or unassociated with the AP (e.g., AP302). However, NDP measurement frames in 802.11ac are typically performed only in the associated mode using a short identity called AID allocated by the AP. The EFTM protocol negotiation system may provide a different identity for unassociated STAs.

During the capabilities exchange phase330, the AP302may send a beacon frame301to STA322. The STA322may send an EFTM request303in order to request an FTM service from the AP302. The AP302may respond with an acknowledgment (e.g., Ack304) indicating that it has received the EFTM request303. Further, the AP302may send an EFTM response305to the STA322. In turn, the STA322may respond with an acknowledgment (e.g., Ack306), acknowledging the reception of the EFTM response305. The EFTM request303and the EFTM response305may include one or more new IEs for supporting the enhanced VHT MIMO parameters. During the capabilities exchange phase330, an EFTM protocol negotiation system may include a negotiation phase for the EFTM protocol to enable the AP302and the STA322to discover and perform capability exchange while being backward-compatible with the existing legacy REVmc protocol such that an IEEE 802.11az STA can communicate with a VHT AP legacy STA supporting legacy FTM in a legacy compatible way, while using the new operational mode when both the AP and the STA are IEEE 802.11az capable. For example, the EFTM protocol negotiation system may facilitate the STA322, which may be an IEEE 802.11az STA, to transmit the EFTM request303, in post discovery (e.g., using a passive scan beacon). The EFTM request303may include at least one new IE for supporting the enhanced VHT MIMO parameters (e.g., number of supported TX chains, number of supported RX chains, supported BWs, etc.) together with its legacy capabilities (e.g., existing REVmc FTM parameters, location context identifier (LCI) request indication, etc.).

In one embodiment, the EFTM protocol negotiation system may be configured to allow a legacy AP to ignore the newly defined IE (normal 802.11 operation) and may respond with a legacy FTM response frame, while an IEEE 802.11az capable AP may respond with a FTM response frame including a new IEEE 802.11az IE providing its capabilities (e.g., BW, number of supported TX chains, number of supported RX chains, LCI for all antennas) and may assign a unique identifier for the unassociated operation unique identifier (UID). The UID allocation311by the AP302may occur when the AP302responds to the EFTM request303. For example, the AP302may allocate a UID to STA322around the time the AP302sends the EFTM response305.

During the capabilities exchange phase330, if the STA322is already associated with the AP302, then both the STA322and the AP302know each other's capabilities. During association, the security context is established. In the case of the EFTM procedure, the security context may be desirable. Consequently, the one or more additional IEs may include an IE associated with the security context that may be exchanged between the AP and the STA.

The UID may be maintained during the repeated measurements phase332using a keep alive process312on the AP302. For example, the STA322may send a null data packet announcement (NDPA)307for location to the AP302to reset the timer. If no NDPA307is received within a certain defined period, the UID may expire and the AP302may assign the UID to another STA322. During the capabilities exchange phase330, the STA322may query the AP302about relevant information for REVmc and IEEE 802.11az measurements, and the STA322may ask for allocation of bandwidth and other relevant parameters and receive the UID for the repeated measurement part instead of the AID. During this phase, the STA322may specify what the periodicity of the measurement procedure is. This may help the AP302and the STA322to later determine if the UID was expired. Examples of relevant unique information for IEEE 802.11az may be the location and geometry of the AP302and the STA322antenna array.

During the repeated measurements phase332, the AP302and the STA322may be involved in multiple measurements in order to determine the range of the STA322to the AP302. For illustration purposes, only one measurement sequence is shown that includes one or more messages (e.g., NDPA307, NDP308, NDP309, and NDP feedback310). This measurement sequence may be repeated as necessary in order to achieve the required FTM measurements.

In the NDP feedback310, the AP302may send the following information: a feedback matrix, the NDP time of arrival (TOA or t1) and the last NDP time of departure (TOD or t4). The UID may be maintained on the initiator device side (e.g., the STA322) using a keep alive process313that may reset a timer associated with releasing the UID for the STA322when an NDP feedback310is received by the STA322. If the NDP feedback310is not received within a certain defined period, the UID may expire and the AP302may assign it to another STA322. However, if the NDP feedback310is received by the STA322before the expiry of the timer, the timer may be reset through the UID keep alive process313.

The termination phase334may be completed by simply letting the UID expire by not performing measurements with the AP for a certain period of time.

The flow ofFIG.3may be backward-compatible and may support legacy devices and REVmc devices in the following way: (1) the AP302may use one bit to signal that the AP302is location capable; (2) the first handshake between the STA322and the AP302may determine if the flow will be for an IEEE 802.11 REVmc FTM or a new flow. The flow ofFIG.3may be such that upon receiving an EFTM request303for FTM measurement that includes an IEEE 802.11az IE and IEEE 802.11 REVmc IE, the AP302may ignore them if it supports only REVmc, and the AP302may reply to them and trigger the new flow if it supports IEEE 802.11az. Further, upon receiving FTM measurement with IEEE 802.11 REVmc IE, the AP302may act as specified in the IEEE 802.11 REVmc, even if it supports revision IEEE 802.11az (e.g., performing a regular FTM procedure as opposed to an EFTM procedure). It is understood that the above descriptions are for purposes of illustration and are not meant to be limiting.

FIG.4depicts an illustrative announcement frame, in accordance with one or more example embodiments of the present disclosure.

Referring toFIG.4, there is shown a frame that may be used for the repeated measurements phase332ofFIG.3.

In the repeated measurements phase332ofFIG.3, the measurement may be done by using a variant VHT sounding measurement. In the start of this phase, the STA may send an NDPA message to the AP. The NDPA message may include one or more fields that may assist the AP in determining information associated with the STA. For example, the NDPA message may include a receiver address (RA)404, a transmitter address (TA)406, a sounding dialogue token408, followed by a series of fields that may include information associated with the STA (e.g., fields410). The STA may signal that this NDPA is an NDPA for location determination by setting one or more of the fields of the NDPA. For example, the sounding dialogue token408may be used to set one or more bits to indicate that this NDPA is for FTM location determination.

The sounding dialogue token408may include a reserved field412and a sounding dialogue token number414. In one embodiment, an EFTM protocol negotiation system may utilize one of the free bits of the reserved field412. By using the free bit, the STA may signal to the AP that a location specific NDP measurement is going to be done next. Using this bit will also signal to the AP to treat the AID field in an STA information field (e.g., field409) as a UID. This way, an AP may allocate 12 bits to AID and 12 bits to UID separately.

The STA information field may include at least in part, an AID field416, a feedback type field418, and a number of columns (NC) index420.

Measurements may be performed periodically. The measurements may also serve as keep alive from the AP and the STA sides keeping the UID valid. If the AP does not receive the NDPA for a predetermined number of periods of time from the STA, or the STA did not receive NDP feedback from the AP for a predetermined number of periods of time as was defined in the capabilities exchange phase330ofFIG.3, the UID may expire and a new UID may be allocated using the repeated capabilities exchange330.

FIG.5Aillustrates a flow diagram of a process500for EFTM protocol negotiation, in accordance with one or more example embodiments of the present disclosure.

At block502, a device (e.g., the user device(s)120and/or the AP102ofFIG.1) may identify an enhanced fine timing measurement (EFTM) request received from a first device (e.g., the user device(s)120and/or the AP102ofFIG.1), the EFTM request comprising one or more information elements (IEs) associated with one or more multiple-input multiple-output (MIMO) parameters, such that this request is enhanced by having additional IEs specific to the IEEE 802.11az specification. The EFTM request may be a variant of a VHT sounding protocol. For example, a user device120may wish to determine its range with respect to an AP102. In order to determine the range, the user device may initiate an EFTM protocol negotiation with the AP102by sending an EFTM request to the AP102. The one or more IEs may be used for supporting the enhanced VHT MIMO parameters (e.g., number of supported TX chains, number of supported RX chains, supported BWs, etc.) together with its legacy capabilities (e.g. existing REVmc FTM parameters, location configuration information (LCI) request indication, etc.). The one or more IEs included in the EFTM request may be ignored by legacy devices such that the FTM procedure can still be completed making the EFTM protocol negotiation backward-compatible. For example, if the AP102and/or the user device120are legacy devices, the one or more IEs may be ignored such that the fine timing measurement seizure can still be completed.

At block504, the device may cause to send an EFTM response to the first device. For example, the AP102may first respond with an acknowledgment indicating that it has received the EFTM request. The AP102may send an EFTM response to the user device120. In turn, the user device120may respond with an acknowledgment, acknowledging the reception of the EFTM response. Similar to the EFTM request, the EFTM response may include one or more new IEs for supporting the enhanced VHT MIMO parameters. These messages may comprise the capabilities exchange phase of an FTM procedure. During this stage, the AP102and the user device120are able to determine how to perform the FTM procedure using their capabilities. Further, the AP102and the user device120may utilize a new addressing mechanism in order to account for the unassociated cases which are not typically included in a sounding procedure. The AP102may allocate a UID to the user device120, which can be used not only in the unassociated mode, but also in the associated mode. However, the AP102may also use either an AID or a UID during the communication with the user device120.

At block506, the device may identify a null data packet announcement associated with a location determination of the first device. For example, after completing the capabilities exchange phase of the FTM procedure, the user device120and the AP102may enter the measurements phase such that one or more control frames are used, instead of management frames, in order to enhance the FTM procedure. During this measurements phase, the AP102and the user device120may be involved in multiple measurements in order to determine the range of the user device120. To start the measurements phase, the user device120may signal that this NDPA is an NDPA for location determination by setting one or more of the fields of the NDPA. For example, a sounding dialogue token field within the NDPA may be used to set one or more bits to indicate that this NDPA is for FTM location determination.

At block508, the device may identify a null data packet received from the first device. For example, the user device120may send an NDP to the AP102.

At block510, the device may cause to send a null data packet feedback to the first device. In the NDP feedback, the AP may send the following information: a feedback matrix, the NDP time of arrival, and the last NDP time of departure. It is understood that the above descriptions are for purposes of illustration and are not meant to be limiting.

FIG.5Billustrates a flow diagram of an illustrative process550for EFTM protocol negotiation, in accordance with one or more example embodiments of the present disclosure.

At block552, an initiating device (e.g., the user device(s)120and/or the AP102ofFIG.1) may cause to send an EFTM request to a responding device (e.g., the user device(s)120and/or the AP102ofFIG.1), the EFTM request comprising one or more information elements associated with multiple-input multiple-output (MIMO) parameters. For example, the initiating device may wish to determine its range to another device such as a responding device, in order to determine the initiator device's location. The EFTM request may be used by the initiating device in order to establish an FTM procedure with the responding device. The EFTM request may include one or more IEs for supporting enhanced VHT MIMO parameters. These MIMO parameters may include at least in part, a number of supported TX chains, a number of supported RX chains, supported BWs, or other parameters, together with its legacy capabilities (e.g., existing REVmc FTM parameters, location context identifier (LCI) request indication, etc.). When the responding device receives the EFTM request, the responding device may respond with an acknowledgment frame in order to acknowledge receipt of the EFTM request. Further, the responding device may respond to the EFTM request by sending either a legacy FTM response or an EFTM response message that may include one or more IEs associated with the MIMO parameters.

At block554, the initiating device may identify an EFTM response from the responding device. The responding device may have responded in either a legacy FTM response or an EFTM response based on the capability of the responding device. That is, if the responding device is a legacy responding device, the legacy responding device may ignore the newly defined IE that was used in the EFTM request sent by the initiating device. The responding device may have signed a UID to be associated with the initiating device during the FTM procedure. The initiating device may receive the response from the responding device and decode the response. After decoding the response, the initiating device may extract information from the response. For example, the initiating device determines the UID based on the extracted information. The initiating device may send an acknowledgment message to the responding device indicating that it has received the response message from the responding device.

At block556, the initiating device may cause to send an NDPA associated with a location determination. The initiating device may employ the use of control frames, such as NDPA and NDP frames, for the repeated measurements to perform an FTM procedure. The NDPA message may include one or more fields that may assist the responding device in determining information associated with the initiating device. For example, the NDPA message may include a receiver address (RA), a transmitter address (TA), a sounding dialogue token, followed by a series of fields that may include information associated with the initiating device. The initiating device may signal that this NDPA is an NDPA for location determination by setting one or more of the fields of the NDPA. For example, the sounding dialogue token may be used to set one or more bits to indicate that this NDPA is for FTM location determination.

Measurement may be performed periodically. The measurements may also serve as keep alive from the responding device and the initiating sides keeping the UID valid. If the responding device does not receive the NDPA for a predetermined number of periods of time from the initiating device, or the initiating device did not receive an NDP feedback from the responding device for a predetermined number of periods of time as was defined in the capabilities exchange phase ofFIG.3, the UID may expire and a new UID may be allocated using the repeated capabilities exchange.

At block558, the initiating device may cause to send a null data packet to the responding device. The initiating device may send the NDP that may help determine the range measurements associated with the FTM procedure. The responding device may respond by sending another NDP to the initiating device.

At block560, the initiating device may identify an NDP feedback from the responding device. In the NDP feedback message, the responding device may send the following information: a feedback matrix, the NDP time of arrival (TOA or t1), and the last NDP time of departure (TOD or t4). The UID may be maintained on the initiating device side by using a keep alive process that may reset a timer associated with releasing the UID for the initiating device when the NDP feedback is received by the initiating device. If the NDP feedback is not received within a certain defined period, the UID may expire and the responding device may assign it to another device. However, if the NDP feedback is received by the initiating device before the expiry of the timer, the timer may be reset through the UID keep alive process. It is understood that the above descriptions are for purposes of illustration and are not meant to be limiting.

FIG.6shows a functional diagram of an exemplary communication station600in accordance with some embodiments. In one embodiment,FIG.6illustrates a functional block diagram of a communication station that may be suitable for use as an AP102(FIG.1) or a user device120(FIG.1) in accordance with some embodiments. The communication station600may also be suitable for use as a handheld device, a mobile device, a cellular telephone, a smartphone, a tablet, a netbook, a wireless terminal, a laptop computer, a wearable computer device, a femtocell, a high data rate (HDR) subscriber station, an access point, an access terminal, or other personal communication system (PCS) device.

The communication station602may include communications circuitry602and a transceiver610for transmitting and receiving signals to and from other communication stations using one or more antennas601. The transceiver610may be a device comprising both a transmitter and a receiver that are combined and share common circuitry (e.g., communication circuitry602). The communication circuitry602may include amplifiers, filters, mixers, analog to digital and/or digital to analog converters. The transceiver610may transmit and receive analog or digital signals. The transceiver610may allow reception of signals during transmission periods. This mode is known as full-duplex, and may require the transmitter and receiver to operate on different frequencies to minimize interference between the transmitted signal and the received signal. The transceiver610may operate in a half-duplex mode, where the transceiver610may transmit or receive signals in one direction at a time.

The communications circuitry602may include circuitry that can operate the physical layer (PHY) communications and/or media access control (MAC) communications for controlling access to the wireless medium, and/or any other communications layers for transmitting and receiving signals. The communication station600may also include processing circuitry606and memory608arranged to perform the operations described herein. In some embodiments, the communications circuitry602and the processing circuitry606may be configured to perform operations detailed inFIGS.2A,2B,3,4,5A and5B.

In accordance with some embodiments, the communications circuitry602may be arranged to contend for a wireless medium and configure frames or packets for communicating over the wireless medium. The communications circuitry602may be arranged to transmit and receive signals. The communications circuitry602may also include circuitry for modulation/demodulation, upconversion/downconversion, filtering, amplification, etc. In some embodiments, the processing circuitry606of the communication station600may include one or more processors. In other embodiments, two or more antennas601may be coupled to the communications circuitry602arranged for sending and receiving signals. The memory608may store information for configuring the processing circuitry606to perform operations for configuring and transmitting message frames and performing the various operations described herein. The memory608may include any type of memory, including non-transitory memory, for storing information in a form readable by a machine (e.g., a computer). For example, the memory608may include a computer-readable storage device, read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices and other storage devices and media.

The machine (e.g., computer system)700may include a hardware processor702(e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory704and a static memory706, some or all of which may communicate with each other via an interlink (e.g., bus)708. The machine700may further include a power management device732, a graphics display device710, an alphanumeric input device712(e.g., a keyboard), and a user interface (UI) navigation device714(e.g., a mouse). In an example, the graphics display device710, alphanumeric input device712, and UI navigation device714may be a touch screen display. The machine700may additionally include a storage device (i.e., drive unit)716, a signal generation device718(e.g., a speaker), an EFTM protocol negotiation device719, a network interface device/transceiver720coupled to antenna(s)730, and one or more sensors728, such as a global positioning system (GPS) sensor, a compass, an accelerometer, or other sensor. The machine700may include an output controller734, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate with or control one or more peripheral devices (e.g., a printer, a card reader, etc.)).

The storage device716may include a machine readable medium722on which is stored one or more sets of data structures or instructions724(e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. The instructions724may also reside, completely or at least partially, within the main memory704, within the static memory706, or within the hardware processor702during execution thereof by the machine700. In an example, one or any combination of the hardware processor702, the main memory704, the static memory706, or the storage device716may constitute machine-readable media.

The EFTM protocol negotiation device719may carry out or perform any of the operations and processes (e.g., processes500and550) described and shown above. For example, the EFTM protocol negotiation device719may be utilized to perform timing measurements between the initiating device and the responding device using control frames as opposed to management frames. Management frames have advantages in terms of negotiation because management frames do not require a response when received. However, management frames require additional processing time. Typically, FTM requires downlink and uplink paths between the initiating device and the responding device so that the initiating device may respond with an acknowledgment to a received FTM frame. A downside of using management frames is that the responding device is responsible for setting the timing of the transmission of the FTM frames. From the perspective of the initiating device, there may be some waiting involved on channel time, resulting in the entire measurement process to have increased power consumption. Further, management frames require increased processing time (e.g., in milliseconds). Typically, control frames have limited and simpler structures than management frames. That means that baseband processing may process control frames using a simpler procedure, resulting in faster processing (e.g., in microseconds). However, control frames are less flexible than management frames. Control frames are fixed in size while management frames are capable of being extended to add new capabilities. Management frames are not limited or fixed in size. Further, control frames do not include information elements, which may be used to extend the management frames.

The EFTM protocol negotiation device719may include a backward-compatible negotiation that may enable the measurement protocol to operate in both the associated and the unassociated modes, and may provide a single capability exchange and allocation negotiation used for multiple measurement exchanges, which minimizes the medium overhead caused by the negotiation.

The EFTM protocol negotiation device719may introduce a capabilities exchange phase that includes the functionality of the negotiation phase of the FTM procedure. The capabilities exchange phase may utilize one or more management frames that may be enhanced to include additional information. The capabilities exchange phase may include one or more information elements (IEs) that may be added to an FTM request frame. A benefit of the management frames as opposed to control frames is that management frames may be modified to include additional IEs. Additionally, a legacy device that receives the FTM request that includes unrecognized additional IEs may ignore those IEs, which in turn makes the EFTM protocol negotiation device719to be backward-compatible with legacy devices. For example, the EFTM protocol negotiation device719may be backward-compatible with the existing legacy REVmc protocol, such that an IEEE 802.11az device may be able to communicate with a VHT access point (AP) or legacy device supporting legacy FTM in a legacy compatible way, while using the new operational mode when both the AP and the device are IEEE 802.11az capable.

The EFTM protocol negotiation device719may utilize one or more control frames during the measurements phase of the FTM procedure. The EFTM protocol negotiation system may keep the flexibility of management frames during the capabilities exchange phase while enhancing the entire FTM procedure by decreasing the time it takes to perform the measurements by using control frames, which do not require as much waiting time between frames as the management frames. The measurements phase may include an exchange of null data packets between the AP and an STA. The NDP is a physical layer (PHY) protocol data unit (PPDU) that carries no data field.

The EFTM protocol negotiation device719may facilitate an IEEE 802.11az STA to transmit an enhanced FTM request, in post discovery (e.g., using a passive scan beacon), that may include a new IE for supporting the enhanced VHT MIMO parameters indicating the capabilities of the STA (e.g., number of supported TX chains, number of supported RX chains, supported BWs, etc.) together with its legacy capabilities (e.g., existing REVmc FTM parameters, location configuration information (LCI) request indication, etc.).

The 802.11ac protocol uses a referencing mechanism for the MAC address that uses what is known as an associated ID (AID) instead of the MAC address. The MAC addresses are typically hardcoded in the devices during manufacturing. However, the AID is assigned to the device during association. Therefore, one additional consideration for the EFTM protocol negotiation device719is to introduce a new addressing mechanism because the MAC addressing is not compatible with it and because the FTM procedure has to operate in the associated and the unassociated modes. In the unassociated cases, addressing is not yet established since the AID would not have been assigned yet. Therefore, the EFTM protocol negotiation device719may facilitate a new addressing mechanism in order to account for the unassociated cases; however, this new addressing mechanism may also apply to the associated mechanism. The new addressing mechanism is referred to hereinafter as an unassociated ID (UID). In the associated mode, a device may use an AID or a UID.

During the capabilities exchange phase, if the device is already associated with the AP, then both the device and the AP know each other's capabilities. During association, the security context is established. In the case of the EFTM procedure, the security context may be desirable. Consequently, the one or more additional IEs may include an IE associated with the security context that may be exchanged between the AP and the STA.

The EFTM protocol negotiation device719may be configured to allow a legacy AP to ignore the newly defined IE and may respond with a legacy FTM response frame, while an IEEE 802.11az capable AP may respond with an FTM response frame including a new IEEE 802.11az IE providing its capabilities (e.g., supported bandwidth, number of supported TX chains, number of supported RX chains, LCI for all antennas) and may assign a unique identifier for the unassociated operation unique identifier (UID). The UID may be maintained using a keep alive process of transmitting a null data packet announcement (NDPA) for location, and resetting the timer. If no NDPA is received within a certain defined period of time, the UID may expire and the AP may assign the UID to another STA.

It is understood that the above are only a subset of what the EFTM protocol negotiation device719may be configured to perform and that other functions included throughout this disclosure may also be performed by the EFTM protocol negotiation device719.

The term “access point” (AP) as used herein may be a fixed station. An access point may also be referred to as an access node, a base station, an evolved node B (eNodeB), or some other similar terminology known in the art. An access terminal may also be called a mobile station, user equipment (UE), a wireless communication device, or some other similar terminology known in the art. Embodiments disclosed herein generally pertain to wireless networks. Some embodiments may relate to wireless networks that operate in accordance with one of the IEEE 802.11 standards.

According to example embodiments of the disclosure, there may be a device. The device may include memory and processing circuitry configured to identify an enhanced fine timing measurement request received from a first device, the enhanced fine timing measurement request may include one or more information elements associated with one or more multiple-input multiple-output (MIMO) parameters. The processing circuitry may be further configured to cause to send an enhanced fine timing measurement response to the first device. The processing circuitry may be further configured to identify a null data packet announcement associated with a location determination of the first device. The processing circuitry may be further configured to identify a null data packet received from the first device based on receiving the null data packet announcement. The processing circuitry may be further configured to cause to send a null data packet feedback to the first device.

The implementations may include one or more of the following features. The null data packet announcement and the null data packet feedback are control frames and the null data packet is a physical layer (PHY) convergence protocol data unit (PPDU) received based on the fine time measurement response. The one or more MIMO parameters include at least one of a number of supported transmit chains, a number of supported receive chains, a supported bandwidth, or a legacy compatibility. The processing circuitry is further configured to allocate a pre-association identification (pre-AID) to the first device. The processing circuitry may be further configured to cause to start a pre-AID allocation timer. The processing circuitry is further configured to cause to maintain the pre-AID allocation to the first device before expiration of the pre-AID allocation timer. The pre-AID allocation timer is associated with a time the enhanced fine timing measurement response is sent to the first device. The processing circuitry is further configured to determine a location of the device based at least in part on measurements of null data packet announcement, the null data packet feedback and null data packet and location configuration information (LCI) extracted from the fine timing measurement response. The null data packet announcement may include an indication of location. The device may further include a transceiver configured to transmit and receive wireless signals. The device may further include one or more antennas coupled to the transceiver.

According to example embodiments of the disclosure, there may be a device. The device may include memory and processing circuitry configured to causing to send an enhanced fine timing measurement request to a device, the enhanced fine timing measurement request may include one or more information elements associated with multiple-input multiple-output (MIMO) parameters. The processing circuitry may be further configured to identify an enhanced fine timing measurement response from the device. The processing circuitry may be further configured to cause to send a null data packet announcement associated with a location determination. The processing circuitry may be further configured to cause to send a null data packet to the device. The processing circuitry may be further configured to identify null data packet feedback from the device.

The implementations may include one or more of the following features. The one or more MIMO parameters include at least one of a number of supported transmit chains, a number of supported receive chains, supported bandwidths, or legacy capabilities. The processing circuitry is configured to identify an unassociated identification (pre-AID) allocated by the device and included in the enhanced fine timing measurement response. The null data packet announcement and the null data packet feedback are control frames and the null data packet is a physical layer (PHY) convergence protocol data unit (PPDU) received based on the fine time measurement response. The processing circuitry is configured to determine a location of the device based at least in part on measurements of null data packet announcement, the null data packet feedback and null data packet and location configuration information (LCI) extracted from the fine timing measurement response. The null data packet announcement may include an indication of location.

According to example embodiments of the disclosure, there may be a non-transitory computer-readable medium storing computer-executable instructions which, when executed by a processor, cause the processor to perform operations. The operations may include causing to send an enhanced fine timing measurement request to a device, the enhanced fine timing measurement request may include one or more information elements associated with multiple-input multiple-output (MIMO) parameters. The operations may include identifying an enhanced fine timing measurement response from the device. The operations may include causing to send a null data packet announcement associated with a location determination. The operations may include causing to send a null data packet to the device. The operations may include identifying a null data packet feedback from the device.

The implementations may include one or more of the following features. The one or more MIMO parameters include at least one of a number of supported transmit chains, a number of supported receive chains, supported bandwidths, or legacy capabilities. The operations further comprise identifying an unassociated identification (pre-AID) allocated by the device and included in the enhanced fine timing measurement response. The null data packet announcement and the null data packet feedback are control frames and the null data packet is a physical layer (PHY) convergence protocol data unit (PPDU) received based on the fine time measurement response. The operations further comprise determining a location of the device based at least in part on measurements of null data packet announcement, the null data packet feedback and null data packet and location configuration information (LCI) extracted from the fine timing measurement response. The null data packet announcement may include an indication of location.

According to example embodiments of the disclosure, there may be a non-transitory computer-readable medium storing computer-executable instructions which, when executed by a processor, cause the processor to perform operations. The operations may include identifying, by one or more processors, an enhanced fine timing measurement request received from a first device, the enhanced fine timing measurement request may include one or more information elements associated with one or more multiple-input multiple-output (MIMO) parameters. The operations may include cause to send an enhanced fine timing measurement response to the first device. The operations may include identify a null data packet announcement associated with a location determination of the first device. The operations may include identify a null data packet received from the first device based on receiving the null data packet announcement. The operations may include cause to send a null data packet feedback to the first device.

The implementations may include one or more of the following features. The null data packet announcement and the null data packet feedback are control frames and the null data packet is a physical layer (PHY) convergence protocol data unit (PPDU) received based on the fine time measurement response. The one or more MIMO parameters include at least one of a number of supported transmit chains, a number of supported receive chains, supported bandwidths, or legacy capabilities. The operations may include allocating an unassociated identification (PRE-AID) to the first device. The operations may include causing to start a PRE-AID allocation timer. The operations may include maintaining the pre-AID allocation to the first device before expiration of the pre-AID allocation timer. The pre-AID allocation timer is associated with a time the enhanced fine timing measurement response is sent to the first device. The operations may include determining a location of the device based at least in part on measurements of null data packet announcement, the null data packet feedback and null data packet and location configuration information (LCI) extracted from the fine timing measurement response. The null data packet announcement may include an indication of location.

According to example embodiments of the disclosure, there may include a method. The method may include identifying, by one or more processors, an enhanced fine timing measurement request received from a first device, the enhanced fine timing measurement request may include one or more information elements associated with one or more multiple-input multiple-output (MIMO) parameters. The method may include causing to send an enhanced fine timing measurement response to the first device. The method may include identifying a null data packet announcement associated with a location determination of the first device. The method may include identifying a null data packet received from the first device based on receiving the null data packet announcement. The method may include causing to send a null data packet feedback to the first device.

The implementations may include one or more of the following features. The null data packet announcement and the null data packet feedback are control frames and the null data packet is a physical layer (PHY) convergence protocol data unit (PPDU) received based on the fine time measurement response. The one or more MIMO parameters include at least one of a number of supported transmit chains, a number of supported receive chains, supported bandwidths, or legacy capabilities. The method may further include allocating an unassociated identification (PRE-AID) to the first device. The method may include causing to start a PRE-AID allocation timer. The method may further include maintaining the pre-AID allocation to the first device before expiration of the pre-AID allocation timer. The pre-AID allocation timer is associated with a time the enhanced fine timing measurement response is sent to the first device. The method may further include determining a location of the device based at least in part on measurements of null data packet announcement, the null data packet feedback and null data packet and location configuration information (LCI) extracted from the fine timing measurement response. The null data packet announcement includes an indication of location.

According to example embodiments of the disclosure, there may include a method. The method may include causing to send an enhanced fine timing measurement request to a device, the enhanced fine timing measurement request may include one or more information elements associated with multiple-input multiple-output (MIMO) parameters. The method may include identifying an enhanced fine timing measurement response from the device. The method may include causing to send a null data packet announcement associated with a location determination. The method may include causing to send a null data packet to the device. The method may include identifying a null data packet feedback from the device. The one or more MIMO parameters include at least one of a number of supported transmit chains, a number of supported receive chains, supported bandwidths, or legacy capabilities. The method may further include identifying an unassociated identification (pre-AID) allocated by the device and included in the enhanced fine timing measurement response. The null data packet announcement and the null data packet feedback are control frames and the null data packet is a physical layer (PHY) convergence protocol data unit (PPDU) received based on the fine time measurement response. The method may further include determining a location of the device based at least in part on measurements of null data packet announcement, the null data packet feedback and null data packet and location configuration information (LCI) extracted from the fine timing measurement response. The null data packet announcement includes an indication of location. In example embodiments of the disclosure, there may be an apparatus. The apparatus may include means for identifying, by one or more processors, an enhanced fine timing measurement request received from a first device, the enhanced fine timing measurement request may include one or more information elements associated with one or more multiple-input multiple-output (MIMO) parameters. The apparatus may include means for causing to send an enhanced fine timing measurement response to the first device. The apparatus may include means for identifying a null data packet announcement associated with a location determination of the first device. The apparatus may include means for identifying a null data packet received from the first device based on receiving the null data packet announcement. The apparatus may include means for causing to send a null data packet feedback to the first device.

The implementations may include one or more of the following features. The null data packet announcement and the null data packet feedback are control frames and the null data packet is a physical layer (PHY) convergence protocol data unit (PPDU) received based on the fine time measurement response. The one or more MIMO parameters include at least one of a number of supported transmit chains, a number of supported receive chains, supported bandwidths, or legacy capabilities. The apparatus may further include means for allocating an unassociated identification (PRE-AID) to the first device; and means for causing to start a PRE-AID allocation timer. The apparatus may further include means for maintaining the pre-AID allocation to the first device before expiration of the pre-AID allocation timer. The pre-AID allocation timer is associated with a time the enhanced fine timing measurement response is sent to the first device. The apparatus may further include means for determining a location of the device based at least in part on measurements of null data packet announcement, the null data packet feedback and null data packet and location configuration information (LCI) extracted from the fine timing measurement response. The null data packet announcement includes an indication of location.

In example embodiments of the disclosure, there may be an apparatus. The apparatus may include means for causing to send an enhanced fine timing measurement request to a device, the enhanced fine timing measurement request may include one or more information elements associated with multiple-input multiple-output (MIMO) parameters. The apparatus may include means for identifying an enhanced fine timing measurement response from the device. The apparatus may include means for causing to send a null data packet announcement associated with a location determination. The apparatus may include means for causing to send a null data packet to the device. The apparatus may include means for identifying a null data packet feedback from the device.

The implementations may include one or more of the following features. The one or more MIMO parameters include at least one of a number of supported transmit chains, a number of supported receive chains, supported bandwidths, or legacy capabilities. The apparatus may further include means for identifying an unassociated identification (pre-AID) allocated by the device and included in the enhanced fine timing measurement response. The null data packet announcement and the null data packet feedback are control frames and the null data packet is a physical layer (PHY) convergence protocol data unit (PPDU) received based on the fine time measurement response. The apparatus may further include means for determining a location of the device based at least in part on measurements of null data packet announcement, the null data packet feedback and null data packet and location configuration information (LCI) extracted from the fine timing measurement response. The null data packet announcement includes an indication of location.